Chemistry Blog

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What is a Chemical Reaction?

Before defining Chemical Reaction, its’ important to understand what elements, substances and compounds are, in Chemistry.

In chemistry, an element is a pure substance consisting only of atoms that all have the same numbers of protons in their nuclei. Unlike chemical compounds, chemical elements cannot be broken down into simpler substances by any chemical reaction.

A chemical compound is a chemical substance composed of many identical molecules composed of atoms from more than one element held together by chemical bonds. A molecule consisting of atoms of only one element is therefore not a compound.

Chemical Reaction, a process in which one or more substances, the reactants, are converted to one or more different substances, the products. Substances are either chemical elements or compounds. A chemical reaction rearranges the constituent atoms of the reactants to create different substances as products.

The basis for different types of reactions is the product formed, the changes that occur, the reactants involved and so on.

Types of Chemical Reactions

Combustion Reaction :

A combustion reaction is a type of chemical reaction in which a compound and an oxidant are reacted to produce heat and a new product. The general form of a combustion reaction can be represented by the reaction between a hydrocarbon and oxygen, which yields carbon dioxide and water:

hydrocarbon + O2 → CO2 + H2O

In addition to heat, it’s also common (although not necessary) for a combustion reaction to release light and produce a flame.

In general terms, combustion is one of the most important of chemical reactions and may be considered a culminating step in the oxidation of certain kinds of substances. Though oxidation was once considered to be simply the combination of oxygen with any compound or element, the meaning of the word has been expanded to include any reaction in which atoms lose electrons, thereby becoming oxidized. As has been pointed out, in any oxidation process the oxidizer takes electrons from the oxidizable substance, thereby itself becoming reduced (gaining electrons). Any substance at all can be an oxidizing agent. But these definitions, clear enough when applied to atomic structure to explain chemical reactions, are not as clearly applicable to combustion, which remains, generally speaking, a type of chemical reaction involving oxygen as the oxidizing agent but complicated by the fact that the process includes other kinds of reactions as well and by the fact that it proceeds at an unusually fast pace. Furthermore, most flames have a section in their structure in which, instead of oxidations,  reduction  reactions occur. Nevertheless, the main event in combustion is often the combining of combustible material with oxygen.

Decomposition Reaction :

Chemical decomposition, or chemical breakdown, is the process or effect of simplifying a single chemical entity (normal molecule, reaction intermediate etc.) into two or more fragments. Chemical decomposition is usually regarded and defined as the exact opposite of chemical synthesis. In short, the chemical reaction in which two or more products are formed from a single reactant is called a decomposition reaction.

A reaction is also considered to be a decomposition reaction even when one or more of the products are still compounds. A metal carbonate decomposes into a metal oxide and carbon dioxide gas.

For example, calcium carbonate decomposes into calcium oxide and carbon dioxide:


Metal hydroxides decompose on heating to yield metal oxides and water. Sodium hydroxide decomposes to produce sodium oxide and water:


Some unstable acids decompose to produce nonmetal oxides and water. Carbonic acid decomposes easily at room temperature into carbon dioxide and water:


Neutralization Reaction :

In chemistry, neutralization is a chemical reaction in which acid and a base react quantitatively with each other. In a reaction in water, neutralization results in there being no excess of hydrogen or hydroxide ions present in the solution. The pH of the neutralized solution depends on the acid strength of the reactants.

A neutralization reaction is when and acid and a base react to form water and a salt and involves the combination of H+ ions and OH- ions to generate water. The neutralization of a strong acid and strong base has a pH equal to 7. The neutralization of a strong acid and weak base will have a pH of less than 7, and conversely, the resulting pH when a strong base neutralizes a weak acid will be greater than 7.

When a solution is neutralized, it means that salts are formed from equal weights of acid and base. The amount of acid needed is the amount that would give one mole of protons (H+) and the amount of base needed is the amount that would give one mole of (OH-). Because salts are formed from neutralization reactions with equivalent concentrations of weights of acids and bases: N parts of acid will always neutralize N parts of base.

Neutralization Reaction Equation

acid + base(alkali) → salt + water

Neutralization reaction equation

Neutralization Reaction Example – Formation of Sodium Chloride (Common Salt):
HCl + NaOH → NaCl + H2O

Redox Reaction :

Redox (reduction–oxidation) is a chemical reaction in which the oxidation states  of atoms are changed. Redox reactions are characterized by the actual or formal transfer of electrons between chemical species, most often with one species (the reducing agent) undergoing oxidation (losing electrons) while another species (the oxidizing agent) undergoes reduction (gains electrons). The chemical species from which the electron is removed is said to have been oxidized, while the chemical species to which the electron is added is said to have been reduced. 

Example of Redox Reactions – Reaction Between Hydrogen and Fluorine

In the reaction between hydrogen and fluorine, the hydrogen is oxidized whereas the fluorine is reduced. The reaction can be written as follows.

H2 + F2 → 2HF

The oxidation half-reaction is:  H2 → 2H+ + 2e–

The reduction half-reaction is:  F2 + 2e– → 2F–

The hydrogen and fluorine ions go on to combine in order to form hydrogen fluoride.

Precipitation or Double-Displacement Reaction :

Double displacement reactions may be defined as the chemical reactions in which one component each of both the reacting molecules is exchanged to form the products. During this reaction, the cations and anions of two different compounds switch places, forming two entirely different compounds.

The general equation which represents a double displacement reaction can be written as:

AB + CD  –>  AD + CB

The easiest way to identify a double displacement reaction is to check to see whether or not the cations exchanged anions with each other. Another clue, if the states of matter are cited, is to look for aqueous reactants and the formation of one solid product (since the reaction typically generates a precipitate).

Double displacement reactions generally take place in aqueous solutions in which the ions precipitate and there is an exchange of ions.

For example, on mixing a solution of barium chloride with sodium sulphate, a white precipitate of barium sulphate is immediately formed. These reactions are ionic in nature. The reactants changes into ions when dissolved in water and there is an exchange of ions in solution. This results in the formation of product molecule.

Double displacement reactions can be further classified as neutralization, precipitation and gas formation reactions.

Neutralization reactions are a specific kind of double displacement reaction. An acid-base reaction occurs, when an acid reacts with equal quantity of base. The acid base reaction results in the formation of salt (neutral in nature) and water.

Precipitation is the formation of a solid in a solution or inside another solid during a chemical reaction. This process usually takes place when the concentration of dissolved ions in the solution exceeds the solubility product.

Synthesis Reaction:

Synthesis reactions are reactions that occur when two different atoms or molecules interact to form a different molecule or compound. Most of the time, when a synthesis reaction occurs, energy is released and the reaction is exothermic. However, an endothermic outcome is also possible. Synthesis reactions are one of the major classes of chemical reactions, which include single displacement, double displacement, and combustion reactions.

The general form of a synthesis reaction is:

A + B → AB

Examples of synthesis reactions:

2 H2(g) + O2(g) → 2 H2O(g)

Carbon dioxide:
2 CO(g) + O2(g) → 2CO2(g)

3 H2(g) + N2(g) → 2 NH3(g)

Aluminum oxide:
4 Al(s) + 3 O2(g) → 2 Al2O3(s)

Iron sulfide:
8 Fe + S8 → 8 FeS

Potassium chloride:
2 K(s) + Cl2(g) → 2 KCl(s)

Book Review: ‘Stuff Matters’ by Mark Miodownik – Exploring the marvelous materials that shape our man-made world.

Author:                        Mark Miodownik

Publisher:                    Houghton Mifflin Harcourt

Publication Date:        May 27, 2014

Print length:                272 pages

Stuff Matters: Exploring the Marvelous Materials That Shape Our Man-Made World takes the reader through a fascinating journey of discovery as the author studies ordinary objects to uncover fascinating secrets about the materials that make our physical world together. From the cultural impact of plastic to modernization of self-healing concrete, Miodownik takes the reader through a microscopic look at everyday things we hardly notice, revealing the engineering marvels that infiltrate our lives. An absorbing contemplation on why materials look and act the way they do; Stuff Matters will teach the reader to see the material world (rather the world of martials) in a completely new approach.

The real difference between materials are deep below the surface, a world that is shut off from the most unless they have access to sophisticated scientific equipment.

The author narrates the story of ten ingredients which provide us with much of the substance that ambiances us. Midownik expresses his passion for the useful, emotive, and sensory aspect of materials such as steel, concrete, ceramics, polymers, glass, and more. Arguably the most interesting chapter for the average reader may be the one on paper. In his commentary on paper, Midownik describes all the different aspects of paper- from the wrapping paper to the office stationary. This thousands of years of old technology is gradually leaving from our lives as the digital ecosphere replaces printing or writing letters on sheets of paper.

Although the Pantheon survived the fall of the Roman Empire, concrete as a material did not.

to the author, another Roman invention, concrete is almost as enduring as books. The author explains how Roman Empire used concrete to construct some of its longest-lasting structures, like the dome of the Pantheon, which has stood for more than 20 centuries and remains the world’s oldest unreinforced concrete structure. Miodownik further elaborates on how, despite its sturdiness, concrete’s fragility had become a problem, the Romans were unable to solve. When he turns to plastics, Miodownik celebrates celluloid, which he said has had the largest cultural impact. Without it, film would have been impossible. The author also takes a moment to talk about craft inventions that were created before the scientific age. Miodownik concludes that materials are so much more than “blobs of differently colored matter”—they are marvels, and looking at them a little closer allows us to gain insight into the reasons they look and act the way they do.

The author’s thoughtful and careful study of ingredients makes that the vivid reader will never look at our everyday stuff the same way again. Both the knowledgeable author and the interesting storyteller in him, deserve the readers’ praise for opening their eyes to the deeper value of objects and materials that often ignore.

Book Review: Molecules: the elements and the architecture of everything by Theodore Gray

The Author –  Theodore Gray

Photographs by Nick Mann

Published on – 2014

Published by – Black Dog & Leventhal 

ISBN 9781579129712

The hundred or so Elements of the Periodic Table, are finite and Molecules are not. There may be only seven different chess pieces but the combinations which can be made on the board by these seven pieces are unlimited. Though there are almost as many categories of Molecules as there are Molecules, that’s why the author Theodore Gray has chosen to write about only the interesting Molecules, the ones that illustrate deeper connections and border concepts that unify them all.

The world of compounds is so wide and diverse that you could make up a large chemistry set focused on even a tiny fraction of it.

If your expectation is a Chemistry Text Book with standard presentation of compounds, this books goes way far beyond that. In its presentation, this is a typical coffee table kind of a book with nice pictures but it had turned out to be a lot more. Supported by Nick Mann’s beautiful photographs, Molecules is a serious attempt to explain the world of chemical compounds to the reader without assuming previous science knowledge.

Gray begins with an explanation of how atoms bond to form molecules and compounds, as well as the difference between organic and inorganic chemistry. He then goes on to explore the vast array of materials molecules can create, including: soaps and solvents; goops and oils; rocks and ores; ropes and fibers; painkillers and dangerous drugs; sweeteners; perfumes and stink bombs; colors and pigments; and controversial compounds. Finally, Gray concludes his commentary on compounds with the most horrible and very bad inorganic compound ever, Asbestos.

Though there is no chapter specially on acids and bases in this book, the first three chapters familiarize the reader with the notions of atoms, elements and chemical structures. The sections ‘compounds’ and ‘molecules’ give simple but meaningful introductions to ionic and covalent bonds. The readers will surely appreciate how Gray has added his personal touch to every segment of text by carefully compiling historic, scientific and other facts into concise, clear and easy to read chunks of knowledge, throughout the book.

Nick Mann, the photographer has done every justice to this book by capturing very clear and striking photographs of the elements and molecules, as well as diagrams of the compounds. He has captured molecules in their various states and their chemical bonds as well. These pictures go wonderfully alongside the chemical structures; which Gray chose to depict with a diffuse glow around the atoms: a reminder that molecules aren’t little balls connected by sticks but rather an assembly of nuclei surrounded by fuzzy electron clouds.

At the designated price, this book is well worth for the money and will make even a fantastic present for a science lover.

Book Review: The Disappearing Spoon by Sam Kean

The Book – The Disappearing Spoon: And Other True Tales of Madness, Love, and the History of the World from the Periodic Table of the Elements

The Author –  Sam Kean

Published on – July 12, 2010

Published by – Little, Brown and Company 

This book can be described as the story telling at its best. The author, Sam Kean describes the evolution of the periodic table with real life stories on how the elements were discovered by their inventors. Kean narrates about the lives of these inventors such as  Marie Curie and Pierre Curie and how their findings impacted on the industry as well as their personal lives. For example, how the  theoretical physicist Maria Goeppert-Mayer facing comparative disadvantages owing to her sex, though she won the Nobel Prize in Physics for her outstanding work.

Then this Pons and Fleischmann story about “Cold Fusion” might be one of the top stories that this book carries.  In 1989, two electrochemistsMartin Fleischmann and Stanley Pons, reported that their apparatus had produced excess heat of a magnitude they asserted would defy explanation except in terms of nuclear processes. Kean describes how this experiment made and unmade Pons and Fleischmann within a few months of time, from being a part of historical scientific breakthrough to being a part of a well-orchestrated con act.  

Pons and Fleischmann with their apparatus of “Cold Fusion” experiment

From “Cold Fusion” story of Pons and Fleischmann, Kean makes his way to introduce pathological science by narrating the story of William Crookes. Due to the grief of the tragic loos of his brother, William Crooks has turned to spiritualism to try to communicate with his brother. He published “Notes of an Enquiry into the Phenomena Called Spiritual” in 1874 and his coworkers thought he was crazy. Crookes eventually left the spiritual research and returned to science and focused on other topics. He finally ends up being a key contributor to the body of knowledge of chemistry.

The theme of each chapter – politics, money, war, the arts, health, toxins, radiation and so on – is prescribed by groups of elements in the periodic table and the things they tell us about the nature of matter; about the stardust origins of the elements; about the compounds they make and why some elements are more reactive than others; and why the table falls into a pattern so obvious that its begetters were able to predict the characteristics of elements not yet identified. The pace is enthusiastic, the tone and language are pitched at the young or the non-chemical and the examples are pleasingly unexpected.

Kean tells the story of Robert Falcon Scott’s expedition to the South Pole. Many scientists were attempting to be the first people to reach the South Pole, but a team led by Roald Amundsen had already reached it. The Amundsen team safely returned from the journey, but Scott’s team was delayed at the pole due to snow flurries and fuel supplies lost due to the high temperatures. Robert Falcon Scott and his companions died on the South Pole.

Kean discusses elements that were put through extreme temperatures to be able to get a sample. Xenon and krypton were put to temperatures as low as −240 F. Kean explains how laser beams are produced by yttrium and neodymium. Kean states that the most powerful laser has more power than the US and it uses crystals of yttrium spiked with neodymium. While lasers produce visible light, masers do not, instead produce microwaves. Masers were considered impossible until Charles Townes worked on them, earning him a Nobel Prize in 1964.

Kean should get the credit for coming up with a book on the subject of chemistry which even a non-chemist can read end to end in a one go due to Kean’s demonstrated ability of top story telling.

The enthalpy change for a reaction between a strong acid and a strong alkali

Aim / Objective: 

To determine the enthalpy change for a reaction between a strong acid and a strong alkali.

Introduction:  Enthalpy is defined as the total energy in a system.  The change in energy ∆H can be positive in heat absorbing (endothermic reactions) or negative in heat releasing (exothermic reactions). This experiment focuses on one form of enthalpy change which is enthalpy of neutralization (∆Hn).  Enthalpy of Neutralization is the enthalpy change observed when one mole of water is formed when a base reacts with an acid in a thermodynamic system.

The literature standard enthalpy for a strong acid-base reaction is -57.1kJ/mol. For weak acids and bases the heat of neutralization is different as they are not fully dissociated and hence some heat will be absorbed.

Materials/ Apparatus:

1.0M HCl solution, 1.0M NaOH solution, 2 measuring cylinders, 2 Styrofoam cups, 2 beakers, 1 thermometer, 1 glass stirring rod.

Method / Procedure:

  1. Use a measuring cylinder to measure 50cm3 of sodium hydroxide (NaOH) and pour into a Styrofoam cup.
  2. Use a thermometer to measure the temperature of the NaOH. Record the reading.
  3. Use a measuring cylinder to measure 50cm3 of hydrochloric acid (HCl) and pour into a Styrofoam cup.
  4. Use a thermometer to measure the temperature of the HCl. Record the reading.
  5. Mix the contents of both cups in a beaker and stir the contents using the glass stirring rod.
  6. Take the temperature after stirring the mixture then record the reading.
  7. Repeat steps 1 to 6 TWO times and then tabulate the results.

Suggested Results:

Experiment numberInitial temperature / °CFinal temperature / °C

Discussion / Calculations:

Heat released = mcΔT

  1. Calculate mass

1000g = 1kg

1000g ÷1000

x = 1kg

50cm3 of acid and 50cm3 alkali = 100cm3 = 1kg

  1. Average temperature = (32+30+30+33.5+30.5+30.5) / 6

= 186.5/6

= 31.08°C

  1. Change in temperature (ΔT) = final temperature – initial temperature

= (46 – 31.08) °C

= 14.92°C

Change °C to K = 14.92 + 273 =287.92

  1. Specific heat capacity = 4.187JK-1kg-1
  2. Heat energy released = mcΔT

= 1kg x 4.187JK-1kg-1 x 287.92K

= 1205.52104J

  1. Enthalpy change = mcΔT / number of moles

50cm3 of acid & base contains (2/1000) x 50

=0.1 moles

0.1 moles H20 = 727.92J

1.0 moles H2O = 727.92J / 0.1 moles

= 7279.2J

Change from J to kJ

7279.2J / 1000 = 7.279kJ

Write the molecular and ionic equation for the reaction

NaOH(aq)   +  HCL(aq)                NaCl(aq) +  H2O(l)

H+(aq)   +    OH(aq)                 H2O(l)

Explain whether the reaction was exothermic or endothermic?

Heat was lost from the mixture to the environment can be said to be exothermic.

What was the use of the Styrofoam cups?

They were used to minimize heat loss of the mixture to the environment.

Chromatographic Methods of separation of substances of a mixture

Chromatography is used to analyze small quantities of a mixture of substances which are chemically similar to each other. It involves the partition of the components of the mixture between a stationary phase and a mobile phase. The mixture to be separated is introduced on the stationary phase which stays still. The mobile phase is then allowed to move over the stationary phase for separation. Partition depends on the different solubilities of the components in the mobile phase and the different adsorption forces of the components with the stationary phase. Adsorption is the temporary attraction of molecules of a gas or liquid to a solid surface. Components with greater solubilities will dissolve into the mobile phase and move along with it readily. Components with stronger adsorption forces will be held on the stationary phase and not move along readily with the mobile phase. The differences in solubilities and adsorption bring about separation.

Paper Chromatography

In paper chromatography, a piece of filter paper or chromatography paper is used which consists of stationary water molecules embedded in a cellulose matrix. The water molecules act as the stationary phase. The mobile phase consists of a suitable solvent that travels up the stationary phase. The mixture to be separated is spotted a short distance from one end of the paper (the base line). The end below the spot is placed in the solvent. As the solvent moves along the paper it carries the mixture with it. The distance the solvent moves from the baseline is called the solvent front. Components of the mixture will separate readily according to how strongly they adsorb on the stationary phase and how readily they dissolve in the mobile phase. If the separated components are colorless, then a visualizing agent can be used to convert them into colored spots. The positions of certain substances can also be determined by fluorescing under a UV lamp. The ratio of the distance moved by a component of the mixture to the distance moved by the solvent is called retention factor. Rf = distance moved by a component distance moved by solvent Each component has a characteristic Rf value for a given solvent under controlled conditions. Thus Rf values of known substances can be used to identify components of a mixture. Paper chromatography is used to analyze mixtures such as dyes in ink, coloring in food additives and amino acids from protein hydrolysis. A visualizing agent such as ninhydrin is used to detect amino acids and amines.

Thin Layer Chromatography (TLC)

This method is similar to paper chromatography. The stationary phase is a thin layer of powered alumna or silica gel which s fixed on to a glass or plastic plate. Plates can be coated with a slurry of the powered adsorbent and then oven – dried. The mixture to be analyzed is spotted near the bottom of the plate. The end below the spot s placed in a suitable solvent. This solvent is the mobile phase and moves up the plate causing the components of the moving solvent. The separated components may be recovered for further analysis by scraping spots off the plate. Thin layer chromatography has the advantage that a variety of adsorbents can be used for separation. It is commonly used to separate amino acids in blood samples and for analysis of food dyes.

Column Chromatography

This method is similar to thin layer chromatography however the stationary phase is packed into a vertical glass column (diameter 1- 2cm) instead of being coated on a plate. A slurry of silica gel or alumina is commonly used for column chromatography. The mobile phase is a suitable solvent which is added to the top of the loaded column. The solvent flows down the column under gravity causing the components of the mixture to partition between the adsorbent and solvent. Each component emerges from the column at different times and can be collected separately. The time between addition of the sample at the top of the column and the emergence of a component at the bottom of the column is called the retention time of that component. Identical substances will have the same retention time under the same conditions thus retention times can be used to identify substances. Column chromatography has the advantage that larger quantities can be separated and therefore can be used to prepare compounds in addition to analyzing them. This method is used in biochemical research and in hospitals to identify amino acids, peptides and nucleotides.

High Performance Liquid Chromatography (HPLC)

This technique is similar to column chromatography however instead of gravity feed, high pressure is used to force the solvent through the column. Columns are smaller than those used in column chromatography, some being 10cm to 30cm long and 4mm in diameter. Retention times are shorter thus rapid analysis of substances can be made. HPLC s used n the industry and hospitals. It is also used to identify suspected stimulants, doping and drugs that may be present in athletes and racehorses.

Gas – Liquid Chromatography (GLC)

GLC uses a longer column than HPLC. It is usually packed with the stationary phase which is an inert powder coated with an non-volatile oil. The column is maintained at a constant, preset temperature in an oven. The mobile phase is an un-reactive gas. The sample to be analyzed has to be in the vapor state at the temperature at which the column is operated. The vaporized sample is carried through the column by the mobile phase. The sample is partitioned between the oil and the carrier gas A detector records each component as it leaves the column at different times. Emerging components can also be fed directly into a mass spectrometer for identification. GLC method of analysis is very sensitive and can be used in forensic testing, to monitor air and water pollution, to detect and identify traces of pesticides or agricultural chemicals in foodstuff and to check dosage of drugs in blood or urine samples.


Saponification can be defined as a “hydration reaction where free hydroxide breaks the ester bonds between the fatty acids and glycerol of a triglyceride, resulting in free fatty acids and glycerol,” which are each soluble in aqueous solutions.

Aim / Objective:

To produce soap using a base-catalyzed saponification of triglycerides.


Soap molecules are the conjugate bases of fatty acids.  Vegetable oils and animal fats are the main materials that are “saponified”. These fats are in fact tri-esters of a glycerol molecule. In the traditional one-step process, the triglyceride is treated with a strong base (e.g., lye), which accelerates cleavage of the ester bond and releases the fatty acid in its conjugate base form, and glycerol.

A General Reaction is as follows:

Saponification Reaction

Saponification using triglycerides

Different alkyl (R) groups are found in different fats and oils.  Depending on which triglyceride (tri-ester) you choose, your soap will have different properties.  For example, some oils make soft or liquid soaps, and some fats make hard soap.


Tripod stand, wire gauze, spatula, breaker, 2 measuring cylinder, glass stirring rod, filter funnel, filter paper, Bunsen burner, 2 test tubes with bungs, test tube rack, evaporating dish, castor oil, concentrated sodium hydroxide (NaOH), distilled water, perfume, dye, saturated solution of sodium Chloride (NaCl)

Method / Procedure:

  1. Half fill a beaker with tap water and set to boil.
  2. Place 2cmcastor oil into evaporating dish. Use a measuring cylinder to pour 10cm3 of concentrated NaOH into the castor oil
  3. Place the evaporating dish atop the beaker of boiling water
  4. Stir the mixture of oil and alkali with a glass stirring rod for 10-15 minutes
  5. Add 10cm3 of the saturated salt solution to the basin and stir the mixture
  6. Turn the Bunsen burner off and leave to cool for 2-3 hours
  7. Use a spatula to scrape the crust of soap which is formed on the side of the evaporating dish
  8. Put this material in a beaker
  9. Add water to the material in the beaker and heat the beaker.
  10. Add a few drops of dye and perfume to the beaker


1. What is the name given to this process?

>>> Saponification

2. Write the word equation for this reaction

>>> Fat/Oil + NaOH        =         Glycerol + Soap (Sodium Salt of Acid)

3. Why is the product of saponification called a salt?

>>> This experiment is the hydrolysis of a fatty acid, usually from lye and fats. The process produces a carboxylate which is a sodium salt.

4. Why was ethanol added to the mixture of fat and base?

>>> Ethanol (ethyl alcohol) is added to the mixture to make the soap transparent. Transparent soap is also known as glycerin.

5. How does soap emulsify fats and oils?

>>> Grease and oil are nonpolar and insoluble in water. When soap is mixed with oils and fats  the nonpolar hydrocarbon portion of the micelles of the soap break up the nonpolar oil molecules. A different type of micelle then forms, with nonpolar oils and fats molecules in the center. Therefore, grease and oil and the ‘dirt’ attached to them are caught inside the micelle and can be rinsed away.

6. Explain the difference in “hard water” and “soft water”

Hard water is any water containing a great quantity of dissolved minerals while soft water is treated water in which the only cation (positively charged ion) is sodium.

7.  Explain which water is better to use with soap

>>>Soap is less effective in hard water as it will react with the ions in the water to form the calcium or magnesium salt of the organic acid of the soap. These salts are insoluble and form grayish soap scum, but no cleansing lather.

Separating a mixture of oil and water using a separating funnel

Aim / Objective:

To separate a mixture of cooking oil and water.


In this experiment, an immiscible mixture of oil and water was separated using a separating funnel.

Materials/ Apparatus:

measuring cylinder, retort stand, beaker, clamp, separating funnel, conical flask, cooking oil and water,

Method / Procedure:

  1. Use a measuring cylinder to measure 10cm3 of cooking oil and pour it into the conical flask.
  2. Use another measuring cylinder to measure 10cm3 of water and add to the conical flask with the oil.
  3. Mix both liquids by shaking the flask vigorously.
  4. Use a clamp to attach the separating funnel to a retort stand. Ensure that the separating funnel is in the closed position and pour in the mixture of oil and water.
  5. Allow the mixture to settle for a few minutes. Place a beaker under the mouth of the separating funnel and allow the mixture of water to run off in the beaker slowly.
  6. Collect the remaining portions of water and oil and then the pure oil.

Diagram of apparatus showing the separation of a mixture of oil and water using a separating funnel

Suggested Results:

When the water was added to the cooking oil, it was seen to be the more dense liquid hence the water settled on top of it. Also in between the layer of pure oil and the layer of pure water, there was a layer consisting of a mixture of oil.

Diagram of apparatus showing the separation of a mixture of oil and water using a separating funnel


1.What type of mixture is the separating funnel generally used to separate?

>>>The separating funnel is generally used to separate a mixture of immiscible liquids. Immiscible meaning that the liquids do not mix but separate into distinct layers

2. Explain why this technique was suitable in separating the oil from the water.

>>>This technique was ideal for the experiment for when water is mixed with oil, it is known to be immiscible. It forms a total of three layers, a layer of pure oil, pure water and a layer of both water and oil mixed together.

3. Explain the chemical principle underlying the type of mixture formed by oil and water

>>>Pure oil doesn’t mix with water because water is polar solvent and oil is non-polar and like dissolves like. But in between the layer of pure oil and pure water there was a layer of both oil and water. This type of technique can be said to be an emulsion.

4.To what position should the top of the funnel be turned when opening it?

>>>The top should be vertical to allow the water to run out and must be closed before the oil reaches the bottom of the funnel

5.Can separating funnel be used to separate a mixture of ethanol and water? Explain your answer

>>>No. A separating funnel cannot be used to separate ethanol and water because ethanol will dissolve in the water due to polarity hence being classified as miscible liquids. So in order to separate a mixture of ethanol and water, one would have to use fractional distillation.

Source of Error/ Limitations/ Assumptions: 

–  Improper technique of decanting, thus allowing for the layers that were collected to be not entirely pure.

Periodic Table Trends

Atomic Radius

The atomic radius of an element is half of the distance between the centers of two atoms of that element that are touching each other. Generally, the atomic radius decreases across a period from left to right and increases down a given group. The atoms with the largest atomic radii are located in group 1 and at the bottom of groups.

Moving from left to right across a period, electrons are added one at a time to the outer energy shell. Electrons within a shell cannot shield each other from the attraction of protons. Since the number of protons is also increasing, the effective nuclear charge increases across the period. This causes the atomic radius to decrease. Moving down a group in the periodic table, the number of electrons and filed electron shells increases, but the number of valence electrons remains the same. The outermost electrons in a group are exposed to the same effective nuclear charge, but electrons are found farther from the nucleus as the number of filled energy shells increases. Therefore, the atomic radius increases.

Ionization energy

The ionization energy or ionization potential is the energy required to completely remove an electron from a gaseous atom or ion. The closer and more tightly bound an electron is to the nucleus, the more difficult it will be to remove, and thus the higher its ionization energy will be. The first ionization energy is the energy required to remove one electron from its parent atom. The second ionization energy is the energy required to remove a second valence electron. The second ionization energy is always greater than the first ionization energy.

Ionization energies increase moving from left to right across a period (deceasing atomic radius). Ionization energy decreases moving down a group (increasing atomic radius). Group 1 elements have low ionization energies because the loss of an electron forms a stable octet.

Electron Affinity

Electron affinity reflects the ability of an atom to accept an electron. It is the energy change that occurs when an electrons is added to a gaseous atom. Atoms with stronger effective nuclear charge have greater electron affinity. Group IIA elements and alkaline earth metals have low electron affinity values. These elements are relatively stable because they have filled “s” sub shells. Group VIIA elements, the halogens have high electron affinities because the addition of an electron to an atom results in a completely filled shell. Group VIII elements, noble gases, have electron affinities near zero, since each atom possesses a stable octet and will not accept an electron readily. Elements of other groups have low electron affinities.

In a period, the halogens will have the highest electron affinity; while the noble gas will have the lowest electron affinity. Electron affinity decreases moving down a group because a new electro would be further from the nucleus of a large atom.


Electro-negativity is a measure of the attraction of an atom for the electrons in a chemical bond. The higher the electro-negativity of an atom, the greater its attraction will be for bonding electrons. Electro-negativity is related to ionization energy. Electrons with low ionization energies have low electro-negativities because their nuclei exert a strong attractive force on electrons. Elements with high ionization energies have high electro-negatives due to the strong pull exerted on electrons by the nucleus. in a group, the electro-negativity decreases as atomic number increases, as a result of increased distance between the valence electron and nucleus (greater atomic radius).

Summary of trends

Moving left to right

  1. Atomic radius decreases
  2. Ionization energy increases
  3. Electron affinity generally increases
  4. Electro-negativity increases

Moving top to bottom

  1. atomic radius increases
  2. ionization energy decreases
  3. electron affinity generally decreases
  4. electro-negativity decreases
Periodic Table Trends

Empirical, Molecular and Structural Formulas

There are three main types of chemical formulas: empirical, molecular and structural. Empirical formulas show the simplest whole-number ratio of atoms in a compound, molecular formulas show the number of each type of atom in a molecule, and structural formulas show how the atoms in a molecule are bonded to each other.

Empirical Formula

The empirical formula shows the simplest whole number ratio of the atoms in a molecule. For example: the empirical formula of hydrogen peroxide is HO.

The determination of the empirical formula of an organic compound involves combustion. A known mass of the compound is burned completely in excess oxygen.

There are several crucial steps in determining the empirical formula of a compound.

Steps for determining an empirical formula

Step 1 – Start with the number of grams of each element, given in the problem. If percentages are given, assume that the total mass is 100g therefore the percent given is equal to the mass of each element present.

Step 2 – Convert the mass of each element to moles using the molar mass in the periodic table

Step 3 – Divide each mole value by the smallest mole that was calculated

Step 4 – Round off to the nearest whole number

Now lets use an example to help us understand exactly how to do this.

Question Compound X contains 45.9% carbon, 32% hydrogen 13.5% nitrogen and 8.6% oxygen. Calculate the empirical formula of compound X.

Step 1 – The mass of each element based on the question

C – 45.9g

H – 32g

N – 13.5g

O – 8.6g

Step 2 – Convert the mass to moles using the molar masses in the periodic table

C          45.9 / 12 = 3.825

H         32 / 1 = 32

N         13.5 / 14 = 0.9643

O         8.6 / 16 = 0.5375

Step 3 – Divide each mole by the smallest number of moles calculated. Remember to round off to the nearest whole number.

C          3.825/0.5375 = 7

H         32 / 0.5375 = 2

N         0.9643 / 0.5375 = 2

O         0.5375 / 0.5375 = 1

Empirical Formula of Compound X – C7H2N2O

Molecular Formula

The molecular formula shows the actual number of atoms of each element in a molecule of the compound. E.g. the molecular formula of the compound hydrogen peroxide is H2O2

Molecular formula can be determined if the molar mass of the compound is known. To find this, calculate the mass of the empirical formula and divide the molar mass of the compound by the empirical formula. Use the number calculated and multiply all the atoms by this ratio to find the molecular formula.

Using an example should make this much easier to understand.

Using the same question above:

Compound X contains 45.9% carbon, 32% hydrogen 13.5% nitrogen and 8.6% oxygen. Calculate the empirical formula of compound X. The molar mass of compound X is 482g/mol

With the empirical formula calculated to be C7H2N2O. We can now go ahead and calculate the molar mass.

C7H2N2O = (7x12g) + (2×1) + (14×2) + (16×1)

84 + 2+ 98 + 16 = 200g/mol

Molar Mass / empirical formula =

482g/mol / 200 g/mol = 2

Therefore multiply the atoms in C7H2N2O by 2

The molecular formula of C7H2N2O is C14H4N4O2

Structural Formula

The structural formula shows the actual number of atoms and the bonds between them; that is the arrangement of atoms in the molecule. The structural formula of hydrogen peroxide is H-O-O-H. The structural formula shows how the various atoms are bonded.

structural formula


Nitinol metal alloy is one of the most useful alloys used for various purposes. It has numerous important medical applications.

What is Nitinol?

It is a nickel- titanium metal alloy with some unique properties. It is also known as Nickel titanium. This alloy exhibits the superelasticity or pseudoelasticity and the shape memory properties. It means this unique metal can remember its original shape and shows great elasticity under stress.

Composition of Nitinol

This metal alloy is composed of nickel and titanium. It contains these two elements at approximately equal atomic percentages. Nickel is a known allergen and it might also have carcinogen properties. Due to this reason the nickel content of this alloy has raised great concerns about its usefulness in the medical industry.

Production of Nitinol

Extremely tight compositional control is required for making this alloy. Due to this reason it is very difficult to prepare this alloy. The extraordinary reactivity of titanium is another obstacle in its preparation. Two primary melting methods are presently used for this purpose:

  • Vacuum Arc Re-melting: In this method, an electrical arc is struck between a water cooled copper strike-plate and the raw materials. Water cooled copper mold is used for melting the constituents in high vacuum to prevent carbon introduction.
  • Vacuum Induction Melting: The raw materials are heated in a carbon crucible using alternating magnetic fields. This is also accomplished in high vacuum; however, carbon is introduced in this process.
Nitinol Picture
3D view of Austenite and Martensite structures of the NiTi compound.

Picture 1 – 3D view of Austenite and Martensite structures of the NiTi compound.

Source –

There are no considerable amounts of data showing the product of one method to be better than the other. Both these methods have different advantages to offer. Other methods like induction skull melting, plasma arc melting, and e-beam melting are also used for this purpose on a boutique scale. Physical vapor deposition process is also used in laboratories.

Symbol of Nitinol

This metal alloy is denoted by the symbols of its constituent metals. The formula for this alloy is NiTi.

History of Nitinol

This material derived its name from its constituents and its place of discovery. In 1962, William J. Buehler and Frederick Wang first discovered the unique properties of this metal at the Naval Ordnance Laboratory.

Commercialization of this alloy was not possible until a decade later. This delay was mainly caused by the difficulty of melting, machining and processing the material.

Properties of Nitinol

The shape memory and superelasticity properties are the most unique properties of this alloy. The shape memory property allows this metal to “remember” its original shape and retain it when heated above its transformation-temperature. It happens due to the different crystal structures of nickel and titanium. This pseudo-elastic metal also shows incredible elasticity which is approximately 10 to 30 times more than that of any ordinary metal.

Here are some basic physical and mechanical properties of this alloy:

Physical Properties

Appearance: this is a bright silvery metal.

Density: The density of this alloy is 6.45 gm/ cm3

Melting Point: Its melting point is around 1310 °C.

Resistivity: It has a resistivity of 82 ohm-cm in higher temperatures and 76 ohm-cm in lower temperatures.

Thermal Conductivity: The thermal conductivity of this metal is 0.1 W/ cm-°C.

Heat Capacity: Its heat capacity is 0.077 cal/ gm-°C.

Latent Heat: this material has a latent heat of 5.78 cal/ gm.

Magnetic Susceptibility: Its magnetic susceptibility is 3.8 emu- gm in high temperatures and 2.5 in low temperatures.

Mechanical Properties

Ultimate Tensile Strength: The ultimate tensile strength of this material ranges between 754 and 960 MPa.

Typical Elongation to Fracture: 15.5 percent

Typical Yield Strength: 560 MPa in high temperature; 100 MPa in low temperature

Approximate Elastic Modulus: 75 GPa in high temperature; 28 GPa in low temperature

Approximate Poisson’s Ratio: 0.3

Making Nitinol Devices

Hot working of this material is relatively easy than cold working. The enormous elasticity of this material makes cold working difficult by increasing roll contact. This results in extreme tool wear and frictional resistance. These reasons also make machining of this alloy extremely difficult. The fact that this material has poor thermal conductivity does not help in this purpose. It is relatively easy to perform Grinding, laser cutting and Electrical Discharge Machining (EDM) on this metal.

Heat treatment of this material is very critical and delicate. The heat treatment-cold working combination is important for controlling the useful properties of this metal.

Nitinol Wires

Nitinol is used for making shape-memory actuator wire used for numerous industrial purposes. This wire is used for guidewires, stylets and orthodontic files. This wire is ideal for applications requiring high loading and unloading plateau-stresses as well as for eyeglass frames and cell phone antennas. However, the main uses of this wire are in stents and stone retrieval baskets.

Nitinol Stent

This alloy is used for manufacturing endovascular stents which are highly useful in treating various heart diseases. It is used to improve blood flow by inserting a collapsed Nickel titanium stent into a vein and heating it. These stents are also used as a substitute for sutures.

Nitinol Basket

Nickel titanium wire baskets are well-suited for many medical applications as it is springier and less collapsible than many other metals. This basket instrument is highly useful for the gallbladder.

Uses of Nitinol

Here are some of the main applications of Nitinol metal alloy:

Medical Applications

  • This alloy is very useful in dentistry, especially in orthodontics for wires and brackets that connect the teeth. Sure Smile (a type of braces) is an example of its orthodontic application.
  • It is also used in endodontic mainly during root canals for cleaning and shaping the root canals.
  • In colorectal surgery, it is used in various devices for the purpose of reconnecting the intestine after the pathology is removed.
  • Nitinol stents are another significant application of this metal in medicines.
  • Its biocompatible properties make useful in orthopedic implants.
  • Nitinol wires can be used for marking and locating breast tumors.
  • The use of Nitinol tubing for various medical purposes is increasing in popularity.

Industrial Uses

  • Nitinol wires are used in model heat engines made for demonstration purposes.
  • This material is used in temperature controls. Its shape changing properties can be used for activating a variable resistor or a switch for controlling the temperature.
  • This metal is often used in mechanical watch springs.
  • It is used as microphone boom or a retractable antenna in cell phone technology for its mechanical and flexible memory nature.
  • Nitinol spring is used in various industries for the purpose of utilizing the superelastic properties of this metal.
  • Nitinol sheets are used for punching, stamping and deep drawing.

Other Uses

  • It is also used as an insert for golf clubs for its shape changing abilities.
  • It is a popular choice for making extremely resilient glass-frames.
  • Nitinol is used for making self-bending spoons used in magic shows.

Availability of Nitinol

Nickel titanium is available in various forms including wires, tubes, sheets and springs. NDC is one of the leading manufacturer and supplier of this metal alloy. However, there are many other suppliers of Nitinol wires, tubes, springs etc. Different forms of this metal are also available online at reasonable prices.

Nitinol is counted among the most useful metal alloys with numerous industrial and medical applications. It is often the best choice for many applications that require enormous motion and flexibility. However, this material has shown fatigue failure in many demanding applications. Experts are working hard for the purpose of defining the durability limits of this metal alloy.



Cesium (Cs) is a metal with atomic number 55, group 1 and period 6. It can be non-radioactive or radioactive. Cesium-137 is one of its most common radioactive forms.

History of Cesium-137

Cesium metal was first discovered in 1860 by two Germans Robert Bunsen and Gustav Kirchhoff while working on flame spectroscopy. Radioactive Cesium with other variants was first discovered in late 1930s.

Cesium-137 Radioactive Source

Non-radioactive Cesium is found naturally in many metals. Cesium-137 is produced when neutron is absorbed by uranium and plutonium and undergoes fission. This process is used in nuclear reactors and nuclear weapons.

Facts of Cesium-137

Some of the important facts about this radioactive substance are as follows:

  • It is only one of the three metals that are liquid in room temperature (83 °F).
  • It is a soft, malleable metal with silvery white color
  • Half-life of Cesium-137 is 30.17 years.
  • Its molecular weight is 136.9071.
  • Its nominal mass is 137 Da, average mass 136.9071 Da, and monoisotopic mass 136.9071 Da.

Picture 1 – Cesium-137
Source –

Uses of Cesium-137

This radioactive substance is used for a number of reasons. Some of its main uses are summed up here:

  • Its strong radioactive nature makes it very useful as isotopes in nuclear weapons, nuclear reactors and industries.
  • It is used as a moisture-density gauge in the construction industry.
  • It is used for detecting liquid flow in pipelines and tanks.
  • This radioactive metal is used in measuring gauges, for calculating dimensions of sheet metal, paper, film and other such products.
  • One of Cesium’s notable usages is in atomic clocks. The speed of vibrations in the element’s outer electrons is recorded and multiplied by 9,192,635,770 to determine a second.
  • In medical science, it is used to treat cancer.

Environmental Exposure of Cesium-137

People are exposed to this substance in very small quantities through soil and environmental fallouts. Exposure to this radioactive substance was mainly because of nuclear tests during the 1950s and 1960s. However, much of it is now decayed. Nuclear accidents such as Chernobyl disaster in Ukraine and fallout of tsunami in Japan in 2011 release some amount of Cesium-137. For instance, water from units 1-4 at Fukushima Daiichi plant has polluted adjoining seawater with this substance. Often, industrial and healthcare equipments containing Cesium-137 are not disposed properly or stolen. In such cases, there is significant risk of contamination.

Health Implications of Cesium-137

If drinking water is contaminated with this metal, it can directly enter the body thereby exposing living tissues to beta and gamma radiation. Human beings may be exposed to it with food or water or through dust. Once inside the body, it spreads uniformly across the soft body tissues. Concentration of this metal is a bit higher in muscles while lower in bones and fats. Compared to many other radionuclides, it remains in the body for a relatively shorter period of time and eliminated through urine. Exposure to this metal can lead to cancer, as is the case with other radionuclides. Very high exposure, which is rare, could lead to serious burns and even death.

Medical Tests to Detect Cesium-137 Presence

There are specialized ways to detect exposure of Cesium-137 to human body, such as a method called “whole-body counting”. There are a number of portable appliances that can measure its level in soft tissue samples from organs or blood, bones, and milk.

Cesium-137 Elimination

Beta particles emission and relatively strong radiation of gamma lead to the radioactive decay of this substance. It degenerates to barium-137m, a short lasting decay output, which then converts to a non-radioactive variant of barium. Half-life of Cesium-137 is 30.17 years. Elimination of this metal is difficult because it moves easily through the environment.



Plutonium-238 is an isotope of plutonium. It is a radioactive substance extensively used as a longstanding fuel source in space probes.

Identification of Plutonium-238

The CAS Registry Number for this radioactive isotope is 13981-16-3.

History of Plutonium-238

Among the different isotopes of plutonium, Pu-238 was the first to be discovered. In 1941, Glenn Seaborg and associates bombarded uranium-238 using deuterons to synthesize Plutonium-238. The intermediate product Neptunium-238 goes through decomposition to form Plutonium-238.

Nucleus of Plutonium-238

There are 144 Neutrons and 94 Protons in the Plutonium-238 isotope.

Symbol of Plutonium-238

The symbol denoting Plutonium-238 is written as 238Pu.

Plutonium-238 Picture

Picture 1 – Plutonium-238

Production of Plutonium-238

Plutonium-238 can be produced by hitting uranium-238 with deuterons. This method is expressed in the following reaction.

238Pu92 + 2D1 → 238Np93 + 21n0

238Np93 → 238Pu94

In the above reaction, Uranium-238 is hit by a deuteron which produces Neptunium-238 and two neutrons, which then undergoes spontaneous decomposition through emission of negatively charged beta particles and forming Plutonium-238 in the process.

Pure Plutonium-238 can be generated by irradiating americium in a nuclear reactor or by irradiating neptunium-237 which is a minor actinide derived while reprocessing spent nuclear fuel. In each case, the derived components are then subjected to a chemical reaction. This involves dissolving the components in nitric acid for extracting Pu-238 from them.

Reactor-grade plutonium obtained from spent nuclear fuel consists of several plutonium isotopes, out of which only 1% or 2% is Plutonium-238. However due to its brief half-life, this small percentage is probably responsible for most of the short-term decay heat produced from the spent nuclear fuel. This is not an effective way for manufacturing Plutonium-238 for Radioisotope Thermoelectric Generators (RTGs) as the spent nuclear fuel would have to go through a difficult process of isotopic separation.

Properties of Plutonium-238

The various Plutonium-238 properties have been discussed below:


It is a solid, bright silvery metal.

Critical Mass

The critical mass of Plutonium-238 for bare sphere is 10 kg.

Critical Diameter

The critical diameter of Plutonium-238 for a uniform sphere is 9.7 cm.

Isotope Mass

The Isotope mass of Plutonium-238 is 238.049553 u.

Decay Mode

Plutonium-238 decay modes include alpha emission, spontaneous fission, 32Si cluster emission and 28Mg + 30Mg double cluster emission.

Decay Energy

Energy released by Plutonium-238 during decomposition is 5.593 MeV.

Branching Ratio

The branching ratio for Plutonium-238 while decaying through alpha emission is 100%.

The branching ratio for Plutonium-238 while decaying through spontaneous fission is 1.9 x 10-9.

The branching ratio for Plutonium-238 while decaying through 32Si cluster emission is 1.4 x 10-16.

The branching ratio for Plutonium-238 while decaying through 28Mg + 30Mg double cluster emission is 6 x 10-17.

Daughter Nuclide

Uranium-234 is produced as a daughter nuclide when Pu-238 undergoes decomposition.

Magnetic Dipole Moment

The magnetic dipole moment of Plutonium-238 is 0 μN.

Spin Parity

Spin parity of Pu-238 is represented as Jπ = 0+ (atomic boson).

Binding Energy

Binding energy per nucleon of Pu-238 is 7.568354 MeV.

Specific Activity

The specific activity SA of Plutonium-238 is 634 GBq/g.

Half-Life of Plutonium-238

In radioactivity, half-life is the time taken by a specific amount of a radioactive substance that undergoes decomposition to be decreased by half. The half-life for Plutonium-238 is 87.7 years.

Radioactive Decay of Plutonium-238

The unstable atomic nucleus of Plutonium-238 loses energy in order to reach a stable stage. This reaction is defined as radioactive decay. Plutonium-238 releases around 5.593 MeV of energy through radioactive decay.

Plutonium-238 Decay Equation

The alpha decomposition of Plutonium-238 is shown in the equation below:

94238Pu → 92234U + 24He

The helium nucleus 24He in this reaction equation has got atomic number 2 and mass number 4. Helium here indicates the alpha particle. This reaction can also be represented in the following way:

94238Pu → 92234U + α

Plutonium-238 Decay Chain

Plutonium-238 goes through decomposition to produce Uranium-234 as the daughter nuclide. At the end of this Alpha decay chain, the stable element that is produced is Lead-206. The complete decay chain is expressed in the following reaction:

Plutonium-238 → Uranium-234 → Radium-226 → Radon-222 → Polonium-218 → Lead-214 → Bismuth-214 → Polonium-214 → Lead-210 → Bismuth-210 → Polonium-210 → Lead-206

Plutonium-238 Fission

Plutonium-238 is not a fissile material and so it is incapable of sustaining chain reactions. However, this substance is fissionable when struck by high energy neutrons.

Uses of Plutonium-238

The various uses of Plutonium-238 are described below:

  • Plutonium-238 is a very strong alpha particle emitter. Since the chances of getting other forms of more powerful and penetrating radiation are minimal, this isotope of Plutonium is used in radioisotope heater units and Radioisotope Thermoelectric Generators (RTGs).
  • This substance produces almost 0.5 watts of heat per gram. It is thus used as an important source of power for fueling interplanetary probes and unmanned spacecrafts. Nuclear batteries using Pu-238 have been used in the Voyager and Pioneer space probes.
  • Trace amounts of Plutonium-238 were also used in manufacturing early pacemaker batteries.
  • A combination of Pu-238 and beryllium produces neutrons which are used in research purposes.

Plutonium-238 Contamination and Health Risks

Plutonium-238 is a dangerous carcinogenic substance. Like Pu-239, Pu-238 is hard to locate once it enters the body and has been absorbed by it.

The main health hazards come from the alpha (α) radiation emitted by Pu-238. These particles are much heavier than the beta and gamma radiation particles and so when they are within the body, they constantly bombard a particular area thereby causing cancer.

Traces of Plutonium-238 mostly get lodged in soft tissues, like in the bone marrow, the liver, on bone surfaces and other non-calcified bony structures. The major threat to human health comes from inhaling this radioactive substance. This can damage the cells and tissues of the lungs and the bronchial tubes. The substance can also enter the body through cuts and abrasions and be absorbed in the blood stream.

Plutonium-238 is one of the most indispensable of all the radioactive isotopes. Without it, the cause of space research would have been much difficult to pursue.



Definition of Iridium-192

It is a radioactive isotope of Iridium with symbol 192Ir.

Sources of Iridium-192

It is a man-made radioactive element that is produced by nonradioactive Iridium metal in a nuclear reactor.

Color of Iridium-192

It is a dense metal that is shiny and silvery-white in appearance.

Properties of Iridium-192

Know about some of the chemical as well as physical properties of this element.

  • Its binding energy per nucleon is 7.938986 MeV (Megaelectronvolts).
  • It has a melting point of 2,446°C.
  • It has a boiling point of 4,428°C.
  • Its specific gravity is 22.562 (at 20°C).
  • It is a dense metal and has a relative density of 22.42.

Fact Sheet of Iridium-192

Know about some important facts associated with this substance.

  • The mass number of this radioactive element is 192.
  • The atomic number of this element is 77.
  • Its neutron number is 115.
  • The atomic mass of this radioactive substance is 191.962605012 u (unified atomic mass units).
  • It has a mass excess of -34.833207 MeV(Megaelectronvolts).

Half Life of Iridium-192

The half-life of this isotopic substance is 73.828 days.


Picture 1 – Iridium-192
Source –

Lifetime of Iridium-192

The lifetime of this radioactive element is 106.51 days.

Decay Modes of Iridium-192

Its decay modes are Beta Particles and Gamma Radiation. It decays 95.13% of the time through negative beta emission to 192Pt (daughter nuclide). For the remaining 4.87% of the time, it decays through electron capture to 192Os. A gamma photon with an average energy of 0.38 MeV (max 1.06 MeV) is released in the process.

Isotopes of Iridium-192

As aforesaid, Iridium-192 is a radioactive iridium isotope. It is also the most common isotope used for high dose rate brachytherapy applications. Once World War II ended, new isotopes such as cobalt-60, caesium-137 and iridium-192 became available for Industrial Radiography. Consequently, the use of radon and radium decreased.

Specific Activity

Its specific activity differs depending on the concentration of 192Ir in the source. For applications of high dose, its specific activity is 2.4×102 TeV/g.

Production of Iridium-192

For commercial use, 192Ir is produced in a nuclear reactor by reaction of 191Ir with neutrons. This technique has numerous benefits. It ensures minimal generation of unwanted isotopes and large cross section of isotopes for interaction of neutrons. As a result, high concentration of 192Ir is produced comparatively easily.

Radiation Safety of Iridium-192

Being a radioactive substance, necessary safeguards must be taken while using it. It should be kept safe in order to avoid accidental exposure or deliberate misuse and disposed following state guidelines. In case of an accidental exposure, victims should remove clothes and discard them permanently. It is important to take showers. Immediate medical help should be sought.

Iridium-192 Applicator

High-dose rate (HDR) Iridium-192 Brachytherapy is often facilitated with the aid of a flexible applicator. It is also used for medical treatment, such as for the cure of stomal recurrence after Tracheostomy is performed for subglottic carcinoma.

Low Dose Supply of Iridium-192

Iridium-192 suppliers render this radioactive element in low doses in wires of 100 – 140 mm in length and 0.3 mm in thickness that can still be cut into smaller pieces as needed. The wires are non-reactive and flexible.

For high dose rate, Platinum/Iridium alloy capsules that are 3.5 mm long and 0.6 mm diameter in size are used. These, used a high 192Ir concentration, provides it with a high activity. The tablet comes coated in Platinum of thickness 1 mm, which weaken the consistency of any electrons produced during decay. The tablet is also welded to the end of a wire allowing it to be deployed using a HDR Remote Afterloading machine.

This radioactive element does not necessarily require sterilizing by end user when deployed for high dose rate (hdr) as it is rendered in a sealed sterilized package.

Uses of Iridium-192

Know about some of the main applications of this radioactive substance.

  • It is a commonly used isotope in high dose rate Brachytherapy.
  • It is also used for medical reasons in Brachytherapy for the treatment of various types of cancer.
  • It also has applications in industrial radiography. It is used to capture x-ray images of heavy metal objects.
  • Radioactive Ir-192 is principally applied for non-destructive testing (NDT). It is also used to a lesser extent as a radio- tracer in the oil industry.

Iridium-192 Implants

Ir-192 implants have medical uses in healthcare industry. These are used for curative reasons, primarily in the breast and the head. These implants are manufactured in wire form and are introduced into the target area through a catheter. The implant wire is removed after being left in place for the time required to deliver the desired dose. This procedure is very effective at providing localized radiation to the tumor site while minimizing the patient’s whole body dose.

Benefits of Iridium-192

There are numerous advantages of using this radioactive element which can be summarized as follows:

  • Its application can be tailored to high or low dose rate, as per requirement.
  • It is relatively easy to manufacture.
  • It has a stable daughter product.
  • It can be reused.

Drawbacks of Iridium-192

Some of the main disadvantages of this element are:

  • Broad spectrum of photons is emitted during the emission process.
  • It involves frequent recalibrations as a consequence of radioactive decay.
  • It needs replacement after every three to four months.

Iridium-192 Cancer Treatment

192Ir is used as a source of gamma radiation for curing cancer with the application of Brachytherapy. Brachytherapy is a type of radiotherapy that involves the placement of a sealed radioactive source inside or adjacent to the region that requires treatment. Specific treatments involve procedures such as:

  • High Dose Rate Prostate Brachytherapy
  • Bilary Duct Brachytherapy
  • Intracavitary Cervix Brachytherapy

Toxicity of Iridium-192

Very little is known regarding the toxicity of iridium compounds. This is due to the fact that they are used in extremely small amounts. However, the radioisotopes of iridium are known to be quite dangerous. The same can be said for 192Ir, which is a radioactive Iridium isotope. Accidental exposure to 192Ir radiation can lead to injuries. High-energy 192Ir gamma radiation can elevate the risk of cancer.

Health Hazards of Iridium-192

External exposure to this substance can lead to problems like

  • Burns
  • Radiation poisoning
  • Acute radiation sickness
  • Death

Internal Iridium-192 exposure can only happen if anyone swallows its tablet or other forms sold commercially. Ingestion of 192Ir can result in burning of the linings of the intestines and the stomach. Swallowed tablets are usually excreted in feces. Long-term effect would depend on how powerful the swallowed contents were and how much duration they stayed in the body. 192Ir as well as other isotopes of Iridium such as 192mIr and 194mIr tend to get deposited in the liver. This can result in health hazards from both gamma and beta radiation.



Xenon-133 is a radioactive isotope of Xenon. It is mainly used for imaging the lungs and also for assessing pulmonary function. This radioactive gas was dispersed into nature during the Fukushima Daiichi nuclear disaster in 2011.

Identification of Xenon-133

CAS Number: 14932-42-4

ChemSpider: 59751

PubChem: 66376

Sources of Xenon-133

It is a fission product of Uranium-235 which means this radioactive gas can be produced by the fission reaction of Uranium-235.

Symbol of Xenon-133

The symbol for this radioactive isotope is 133Xe. It can also be denoted by Xe-133.

Xenon-133 Picture

Picture 1 – Xenon-133

Properties of Xenon-133

Here are some of the basic properties of this radioactive substance:

Appearance: It is a colorless gas.

Odor: This gas does not have any distinctive odor.

Isotope Mass: The isotope mass of this radioactive isotope is 132.9059107 u (unified atomic mass unit)

Decay Energy: It has a decay energy of 0.427 MeV.

Boiling Point: Its boiling point is -108 °C at 1mm.

Radioactive Decay of Xenon-133

The unstable nucleus of this radioactive gas emits ionizing particles in order to lose energy and reach a stable state. It undergoes Beta decay by radiating Beta Rays (β) with 0.427 MeV decay energy. This radioisotope also emits small amounts of Gamma (γ) rays.

Decay Equation of Xenon-133

Following is the decay equation for the Beta (β) decay of this radioactive isotope:

13354Xe → 0-1β + 13355Cs

Decay Chain of Xenon-133

Xenon-133 decays into Cesium-133 which makes it the daughter nuclide of Xe-133. The decay chain of this radioactive isotope is very short as the next element produced in this decay chain is a stable substance. Here is the decay chain:

Xenon-133 → Cesium-133 (stable)

Nucleus of Xenon-133

There are 79 neutrons and 54 protons in the nucleus of a single isotope of this gas.

Half Life of Xenon-133

This Radioactive gas takes 5.243 days to decay and reduce to the half of its original amount.

Xenon-133 in Human Body

This gas neither occurs naturally in human body nor is it used by the body. This diffusible gas passes through the cell membranes while exchanging between tissue and blood. It has a better solubility in body fats than in blood or plasma. It is also a little soluble in aqueous media. The inhaled Xe-133 crosses the alveolar wall entering the venous circulation via the pulmonary capillary bed. Almost all the Xenon-133 gas will be exhaled after returning to the lungs. The whole process takes a short period of time as this radioactive gas has a biological half life of 5 minutes.

Uses of Xenon-133

The Gamma radiation from this isotope is used by means of inhalation in Single Photon Emission Computed Tomography (SPECT) to image the lungs, heart and brain. It is also used for the measurement of blood flow.

Precautions of Using Xenon-133

It is not advisable to administer this radiopharmaceutical preparation to pregnant women as adequate researches have not yet been done to determine its effects on fertility. It should not be used by people having hypersensitivity to this radioactive agent. Radiopharmaceuticals should be used under proper guidance of physicians who are qualified for safe use of radionuclides.

Brand Name of Xenon-133

Xeneisol is one of the most important brand names for this gas.

Xenon-133 is one of the most useful radioactive isotopes of Xenon. It is highly useful in the field of radiopharmaceuticals with a short half life of little over 5 days.



Uranium-238 is a common radioactive isotope of Uranium. It is not a fissile substance thus cannot sustain nuclear fission. However this isotope is a fertile material, which means other fissile materials are generated from it.

Identification of Uranium-238

CAS Number: 7440-61-1

Sources of Uranium-238

Almost all Uranium in nature is found in the form of Uranium-238. Other isotopes like Uranium 234, Uranium 235 and Uranium 236 are found in smaller quantities in natural Uranium.

Chemical Formula of Uranium-238

The formula for this radioactive isotope is 238U. It is also denoted with U-238.


Picture 1 – Uranium-238
Source –

Properties of Uranium-238

The radioactive and physical properties of this substance include:

  • Appearance: It is a hard, silver white metal.
  • Molecular Weight: The molecular weight of this radioactive metal is 236.03 gm/mol.
  • Atomic Number: The atomic number of Uranium-238 is 92.
  • Mass Number: Its mass number is 238.02891(3) u (unified atomic mass unit).
  • Density: The density of this material is 18.95 gm/cm3. It has 65% more density compared to Lead.
  • Solubility: It is soluble in Nitric Acid (HNO3) and Hydrochloric Acid (HCl).
  • Melting Point: It has the melting point of 1,132 °C.
  • Boiling Point: The boiling point of this radioactive metal is 3,818 °C.
  • Specific Gravity: Its specific gravity is 9.1 at 25 °C temperature.

Radioactive Decay of Uranium-238

The unstable atomic nucleus of Uranium-238 emits ionizing particles and loses energy in order to achieve a stable state. This process is called the Radioactive decay. This isotope undergoes Alpha decay by emitting Alpha rays. It has a decay energy of 4.267 MeV.

Decay Equation of Uranium-238

Following is the equation for the Alpha (α) radiation of this isotope:

238U → 23490Th + 42He2+

The above equation can also be denoted as

238U → 234Th+ α

In the first equation the 42He (Helium) is similar to an Alpha particle having mass number of 4 and atomic number 2. Due to this reason it has been denoted by an Alpha particle in the second reaction.

Uranium-238 Decay Chain

Thorium-234 is the next radioactive substance in the decay process of Uranium-238. It means Thorium-234 is the daughter nuclide of this isotope. Lead (stable) is the final element of this Alpha decay process. Following is the complete decay series:

Uranium-238 → Thorium-234→ Protactinium-234m→ Uranium-234→ Thorium-230→ Radium-226→ Rodon-222→ Polonium-218→ Lead-214→ Bismuth-214→ Polonium-214→ Lead-210→ Bismuth-210→ Polonium-210→ Lead-205 (stable)

This series is also known as “Radium Series”. All the above elements are present (even if for a short time) in any sample containing Uranium be it metal, mineral or compound.

Nucleus of Uranium-238

One atom of this substance contains 92 protons and 145 neutrons.

Half Life of Uranium-238

Half life is the time period taken by a radioactive substance to decay and reduce to the half of its original amount. Uranium-238 has a very long half life of 4.468 billon years.

Uranium-238 Fission Reaction

This material does not undergo fission unless struck by a high energy neutron. It collides with a neutron and turns into Uranium 239, which undergoes decay and produces Plutonium-239. This final radioactive isotope is highly useful in power plants.

Uranium-238 uses

This radioactive metal has a very long half life. The Depleted Uranium (DU) is very heavy having a high density level. These properties make this substance useful in various industries.

As a Breeder

Fertile uranium-238 isotope is used in Breeder Reactors for its neutron capture ability. It produces fissile products like Plutonium- 239, which is used as a nuclear fuel to produce high amounts of energy. This technology is used in many experimental nuclear reactors.

As a Radiation Shield

It is used as a shield against harmful radiation in the form of Depleted Uranium Dioxide and Depleted Uranium. The non-radioactive casing of the Shield can easily stop its Alpha radiation from causing any harm. The high atomic weight and electron numbers of this material can efficiently absorb Gamma Rays and X Rays. However, it cannot stop fast neutrons having a speed of 14,000 km/s, as effectively as ordinary water.

Researchers are trying to find out whether Uranium Dioxide concretes can be used as a Cask Storage material for storing radioactive waste.

In Radioactive Dating

The radioactive property of a material is applied to determine the age of objects like rocks and fossils. Uranium-238 is used in this dating process. The decay chain of this isotope is well documented with Lead being the final stable element. The whole decay series happens at a constant rate which helps to correctly date rocks and minerals.

In this process, the age of an object is determined by adding the amount of the daughter product (e.g. Thorium) in the object with the amount of the parent isotope (e.g. Uranium).

In Nuclear Weapons

Uranium-238 is used as a “tamper” material in nuclear weapons. Its function is to reduce the required critical mass and make the weapon work more efficiently. It is used in thermonuclear weapons for the purpose of encasing the fusion fuel which helps to make the weapon more powerful.


Downnblending is the opposite process of enriching. Enriched Uranium is downblended with the help of depleted Uranium for using it as commercial nuclear fuel. It is used to produce Mixed Oxide Fuel (MOX) along with Plutonium- 239.

Is Uranium-238 Harmful for Human Health?

Radioactive Uranium can be found in nature which can cause health problems for humans. It can enter the body through inhalation, ingestion and sometimes through open wounds. However, it cannot harm an organism from the outside as its Alpha radiation does not penetrate the skin.

Most of the Uranium-238 ingested or inhaled usually leaves the body. But a very small amount gets accumulated in the bones. It remains there undergoing radioactive decay for a very long time. This radiation can cause adverse health effects like kidney damage and cancer.

Commercial Supply of Uranium-238

There are many companies who supply this material in different parts of the world.

Uranium-238 is the main radioactive isotope of natural Uranium. It produces many other useful radioactive elements while undergoing decay. This makes this radioactive metal quite useful and valuable.



What is Americium-241?

Americium-241 is a radioactive substance that principally emits Alpha rays. It is one of the most important and useful isotopes of Americium or Am. It radiates Alpha Rays.

In its physical form, it appears as Americium oxide contained within a ceramic cylinder.

Identification Facts of Americium-241

The CAS Registry Number for this material is 14596-10-2.

History of Americium-241

“Am” was first said to be discovered from Plutonium (Pu) in the year 1945. The discovery was announced by well-known chemist Glenn Seaborg who also discovered Pu along with his colleagues.


Picture 1 – Americium-241
Source –

In their first attempt to produce Am Plutonium-239, a radioactive isotope of Pu was bombarded with neutrons containing high energy. The resultant substance was Plutonium-240, which was again bombarded with neutrons to produce Plutonium-241. The decay and subsequent transformation of isotope Plutonium-241 resulted in the formation of Americium-241 following the process of Beta Decay.

This experiment was done at the University of Chicago’s Metallurgical Laboratory (now the Argonne National Laboratory).

Symbol of Americium-241

The symbol used to denote this radioactive isotope is 241Am or Am-241.

Production of Americium-241

These days, the isotope is produced artificially as a decay product of Plutonium-241. It is also a resultant material of nuclear bomb explosions.

Decay of Americium-241

This substance undergoes Alpha decay, meaning it emits Alpha (α) Particles in its process of decay. In addition, it radiates small amounts of Gamma (γ) Ray as a by-product.

Half Life of Americium-241

This radioactive substance has a half life of 432.2 years, meaning it takes 432.2 years to decay and reduce to the half of its initial amount. Half Life is the time needed by a decaying radioactive substance to fall to half of its original value.

Decay Chain of Americium-241

This substance decays and changes into Neptunium-237 (237Np) which makes it the daughter nuclide of 241Am. The ultimate product of this series is Bismuth-209. Following is the complete decay chain:

241Am → 237Np → 233Pa → 233U → 229Th → 225Ra → 225Ac → 221Fr → 217At → 213Bi → 213Po → 209Pb → 209Bi

Decay Equation of Americium-241

Following is the Alpha decay equation for this isotope:

95241Am → 42α + 23793Np

Chemical Properties of Americium-241

Some of the main chemical properties of this substance are as follows:

  • It has the atomic mass of 241.056823.
  • It is a silver colored metal.
  • It mainly undergoes α particle emission, but it also radiates low energy γ particles.
  • The mixture of Am-241 and Beryllium is capable of emitting neutrons. It is efficiently used as a source for neutrons.
  • Its atomic number is 95.
  • In its chemical form, it appears as Americium Oxide.
  • The boiling point for this isotope is 2607°.
  • The melting point for this substance is 994°.
  • The density of this material is 13.67 g/cm3.

Uses of Americium-241

There are many different isotopes of Am, but Am-241 is the most important and useful among all of them. The most important use of this material is as an element of the Smoke Detector. Following are some of its other uses:

  • It is used for various researches.
  • It has applications in different medical diagnostic devices.
  • It is useful in Thickness gauging (the thickness measurement of materials like plastic, metal and paper).
  • It is also used in Fluid-density gauging (measuring the density of fluids).
  • Am-241 is used in Aircraft fuel gauges (A device to indicate the level of fuel in a tank).
  • This isotope is utilized in various distance-sensing devices.

All these applications use Gamma Ray emission. So, the Gamma radiating properties of this isotope are utilized for these purposes.

The European Space Agency is considering the use of 241Am in their space probes.

Americium-241 in Smoke Alarms

Smoke detectors or Smoke Alarms are very important safety devices. Two main types of this detector available in the market are:

  • Ionization chamber Smoke Detectors
  • Photoelectric Smoke Detectors

This substance is an important component for the Ionization Chamber Smoke Detectors. There is a small metal chamber in these detectors that contains a small amount of this substance. The chamber may also use some other radioactive substance for this purpose.

The main function of this device is to detect the presence of smoke caused by fire. The ionizing α radiation from Americium-241 is utilized to create ions that produce a low and steady electric current. When the smoke particles enter the chamber, they create a disturbance and trigger the alarm in the detector.

Radioactive materials are kept to a minimum in the device so that it cannot have any damaging effects of radiation on the human body.

Smoke Detector Precautions of Americium-241

241Am may cause different serious health problems in case of over exposure. While using this device, the following points should therefore be kept in mind:

  • Never try and dismantle the smoke detector.
  • Never try to remove the source of 241Am.
  • Never attempt to burn the device in order to dispose of it.

Any of these actions will expose you to the radioactivity of the material.

Even though it is not illegal to throw your Americium-241 Smoke Detector in the trash, it is best to return it to the manufacturer to dispose it of safely.

Americium-241 Exposure

It is very unlikely for people to come into direct contact with this material. It can have adverse effects on human health in case of inhalation and ingestion.

It was spread into the environment in large amounts during the nuclear weapon testing of 1950s and 1960s and also the Chernobyl Nuclear Disaster of 1986.

Skin contact

In case of accidental exposure of skin to this substance, the exposed region should thoroughly be washed along with water and soap. All clothes and accessories should be removed and cleaned or washed thoroughly before reuse.


Inhaling contaminated air or eating or drinking contaminated food or water may directly expose a person. In case of inhalation, the Am-241 tends to concentrate in the lungs. The amount depends on the form of its chemical compound. The soluble particles dissolve and pass into the bloodstreams. But the remaining substance may stay in the lungs or the stomach. The un-dissolved substance leaves the human body through the feces.


In case of accidental consumption of Am-241, it is necessary to excrete within a short time. Otherwise, it tends to accumulate in the liver and the skeleton and cause serious liver and bone problems and diseases.

Health Hazards of Americium-241

The half life of this material is very long (432.2 years). As a result, it may remain and undergo decay within the body and cause serious health problems for humans. It may even be responsible for causing cancer of the nearby organs and tissues.

External exposure to the γ radiation may also cause cancer of different organs.

Americium-241 Personal Safety Precautions

As aforesaid, exposure to this material can pose acute health risks. This is a toxic material that needs to be handled carefully.

Protective Gear

Special protective equipments like gloves, safety goggles and footwear covers should be used while dealing with Am-241 in industries. People using this substance should also ideally wear proper respiratory equipments to avoid ill-effects due to inhalation of this material.

Accidental Spillage

In case of accidental release or spillage of this material, everyone in the vicinity should be immediately alerted. The region should be evacuated and an absorbent material should be used to suck the dispelled substance. The waste should be disposed of in separate containers and aid should be summoned.

Americium-241 Exposure Tests

There are different tests to determine the amount of this material in different parts of an organism. These tests are useful in treating patients of Am-241 over-exposure. All these tests need special equipments to be carried out.

Though it is most important among all the radioactive isotopes of Am, it has the potential to cause critical health problems for humans. Care should be taken that there is no possibility of exposure for anyone using any application containing Am-241.


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