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Chemical Reactions

What is Chemical Reaction?

chemical reactionA chemical reaction is an interaction which occurs between two or more than two substances to form a new substance. For example, oxygen and hydrogen react with each other to form a new substance called water (H2O). Chemical reactions happen all the time around you, even without your notice. The food that you eat goes to your stomach and there it reacts with many chemicals including acids to digest the food. Other examples of everyday life chemical reactions include; rusting of iron, burning of wood, photosynthesis, and combustion in the cars.

Substances that chemically react with each other are called reagents and reactants. Reactants are consumed in the reaction. The new substance that is formed is called the product of the reaction.

Why do Chemical Reactions happen?

Chemical reactions occur because molecules of different substance interact with other, in such a way that chemical bonds are broken and formed.

Equation of the Chemical Reaction

Chemical reactions need to be expressed in the simple form so that it can be understood easily. For this reason, chemists use chemical equations. Chemical equations use the symbol for elements and molecular formula for the compounds to express the substances.

The reacting substances are placed on the left side. Whereas, newly formed substance are placed on the right side of the equation. Both left and right of the equation are separated by symbol (→). The head of the arrow is used to point in the direction of the reaction; from reacting substances to products.

Types of Chemical Reaction

There basically four types of the chemical reaction, which are:

  1. Synthesis reaction:
    In this type of reaction, two or more than two substance react with each other to form a new substance (product). For example, Carbon from coal and oxygen from the atmosphere will react to produce carbon dioxide. The equation of the reaction is C + O2 –> CO2.synthesis-reaction
  2. Decomposition reaction:
    When a substance is broken down into its constituent parts, then it is called decomposition reaction. For example, water is decomposed into its constituent parts, which are hydrogen and oxygen with help of electrolysis. You can consider this reaction as opposite of synthesis reaction. The equation of the reaction is H2O –> H2 + O.decomposition-reaction
  3. Single Replacement reaction:
    In this type of reaction, an element will replace another element which is already part a substance. For example, if a substance AB is composed of element A and B, reacts with the element C. If this element C takes the place of B in the reaction will result in the formation of new substance AC, and release of element B. The equation of the reaction is AB + C –> AC + B.single-replacement-reaction
  4. Double Replacement reaction:
    In this type of reaction, two substances will exchange their constituent elements, resulting in the formation of two new substances. For example, a substance AB is made of element A and B, reacts with other substance CD, which is composed of element C and D. Now in the reaction they will exchange their constituent elements; element B and D will exchange their position. The equation of the reaction is AB + CD –> Ad + CB.double-replacement-reaction


  • In a chemical reaction, new substances are created from reacting substances.
  • Chemical reactions can produce heat and light. For example, burning of wood.
  • Many rockets use the reaction of oxygen and hydrogen for their propulsion.

Chemical Bonding

What is Chemical Bond?

A chemical bond is an attractive force that binds atoms together to form new compounds. These bonds are formed in a process called chemical reaction.

So, how these bonds are formed? To understand this concept, let’s first understand the structure of an atom.

Structure of an atom

An atom consists of electrons, protons, and neutrons. Protons and neutrons are placed together in the nucleus; the center part of an atom. Whereas, electrons orbit around the nucleus at certain distances known as shells. The number of electrons in a normal atom are equal to number protons, and the atom is said to be neutral.carbon-atom

Each shell of an atom has a certain capacity for holding electrons. So, when lower shells become filled, electrons occupy upper shells to accommodate themselves. The outermost shell of an atom is called its valence shell. The first shell can accommodate 2 electrons, the second shell can 8 electrons, and the third shell can 18 electrons. (Read more at what is atom).

Why is Chemical bond formed?

Atoms always try to completely fill their valence shell with electrons to become stable. But, the number of electrons in an atom depends on the number of protons. So, mostly atoms can’t fill their valence shell completely. For example, oxygen has 8 protons, so it will carry 8 electrons. These electrons will accommodate in the shells as follow: two electrons will go to the first shell and the remaining six electrons will go to the second shell (here the second shell is valence shell). But as described previously, the second shell can carry 8 electrons, but here only 6 electrons are going to it. This will make the oxygen atom unstable, so oxygen atom will somehow try to get these remaining two electrons to complete its shell, or it will try to lose these 6 electrons to make the first shell as valence shell. For that reason, atoms will make chemical bonds with other atoms to complete their shells.

Types of chemical bond

There are basically two main types of chemical bond. Which are:

  1. Ionic bond
  2. Covalent bond

Although, there more than two types of bonds. But, here only two types of the bonds will be discussed.

Ionic bond

In this type of bond, atoms will completely transfer their electrons between each other to complete their shells. Ionic bond will occur between the atoms of different elements and mostly occurs between metals and non-metals.


lithium has 3 electrons in its shells. Lithium has to donate one electron or borrow seven electrons from another atom to complete its valence shell. But, donating one electron is easier than borrowing seven electrons so Lithium can act as a donor. Similarly, fluorine has seven electrons in its valence shell and it needs one extra electron to complete its valence shell.Chemical bond of lithium floride

If Lithium donates one electron to Fluorine, they both can complete their valence shell. By doing so, both atoms will become electrically charged. Now, Lithium will have more protons than electrons so it will become positively charged lithium ion, and fluorine with increased number of electrons will become negatively charged fluorine ion. This charge difference between them will create an electrostatic force of attraction between them. As a result, both atoms will be attracted to each other and will be held together. This way a new substance will be made called Lithium Fluoride (LiF).

Covalent bond

In this type of bonding, electrons are shared between atoms to complete their valence shells rather than transferring their electrons. Electrons are shared in pairs; each atom has to share same number electrons to make pairs. Shared electrons become part of each covalently bonded atom. They constantly circulate between them. This type of bond mostly occurs between non-metals.


The oxygen atom has 6 electrons in its valence shell, and hydrogen atom has one electron in its valence shell (which is also its first shell). Oxygen needs two electrons to complete its shell and hydrogen needs one electron. So, oxygen takes two hydrogen atoms and shares its one electron with each hydrogen atoms. Hydrogen atoms also share their one electron with oxygen. So, two pairs of electrons (4 electrons) are shared in this bond.Chemical bond of water - H2O

Oxygen has four shared electrons, and four remaining electrons in the valence shell, which make its valence shell complete. Both hydrogen atoms have one shared pair of electrons (2 electrons), which make their valence shell (in this case, first shell) complete.

In this bond oxygen and hydrogen atoms that are held together due to sharing of electrons. This new substance which formed as a result of their bonding is called water (H2O).


  • Valence shells of noble gases are complete. So, they don’t form any bond in normal condition.
  • Common table salt (NaCl) is formed when Sodium donates its one electron to chlorine gas.
  • Atoms in a bond are held together due to the electrostatic

How to Make Foamy Fountain

Make this interesting colored foamy fountain at home and enjoy its beauty! The foam that is produced by fountain is special because each bubble is filled with oxygen gas. You will learn how this fountain works and what science is behind it.

Required Materials

  • Empty plastic bottle about 500ml (half liter) in volume
  • ½ cup of Hydrogen Peroxide (20-volume or 6%)
  • 1 Tablespoon of Yeast
  • Liquid dish soap
  • Food coloring


  1. Pour ½ cup of hydrogen peroxide in the bottle. Be careful! When dealing with hydrogen peroxide. It can irritate skin so let an adult to handle it.
  2. Add few drops of food coloring of your choice into the bottle.
  3. Add 1 tablespoonful of liquid dish soap into the bottle. Close the bottle with cap and swish it so that all the liquids mix together.
  4. Take a cup and add 3-4 tablespoons of water and 1 tablespoon of yeast in it. Stir the cup with spoon to mix the water and yeast together.
  5. Your fountain is ready. When it is time to start fountain just add water-yeast mixture into the bottle.

Fountain will expel the foam out of the bottle so you should do this experiment at washable area of your home.

Foamy Fountain


This Foamy Fountain is the breaking of hydrogen peroxide into water and oxygen gas with the help of yeast that acts as a catalyst. Sudden release of oxygen cause rapid bubbling of gas because of soap in the bottle. These bubbles rush out of bottle because new bubbles are constantly created.


  1. Increase the amount of yeast added in the bottle and find out! Does it affect the rate of reaction?
  2. Increase the amount of Hydrogen Peroxide and also add some water in the bottle and find out! Does it affect the timing of the fountain?

How to Inflate Balloon with Vinegar and Baking Soda

Inflating balloon with vinegar and baking soda is a classic experiment. Perform this experiments with friends and explain them what is happening. You can perform this experiments with materials from your kitchen. In this experiment you will learn you will learn how gas (carbon dioxide) produced from chemical reaction inflates the balloon.

Required Materials

  • One Empty Plastic Bottle
  • Half Cup of Vinegar
  • A Balloon
  • 2 to 3 Spoons of Baking Soda
  • Water

What To Do

  1. Pour the ½ cup of vinegar and ¼ cup of water in the plastic bottle.
  2. Inflate and deflate the balloon with your mouth 2 times to loosen it. Pour 2 spoonful of baking soda in the balloon using funnel (If you don’t have funnel than you can make one from paper and scotch tap).
  3. Stretch open the mouth of the balloon and carefully put it over the neck of the plastic bottle. Let the end of the balloon dangle to prevent the baking soda from falling into the bottle.
    Balloon with baking soda
  4. Hold the mouth of balloon tightly on neck of the bottle and hold the other end of balloon up so that all the baking soda goes into the bottle.

Observe the inflating balloon and chemical reaction.

inflating balloon


When Baking soda is added to vinegar, an acid-base reaction takes place. In this reaction carbon dioxide gas is produces which develops pressure in the bottle and starts to inflate the balloon that means your balloon is full of carbon dioxide gas so it won’t float in the air because carbon dioxide is heavier than air. Adding water in the bottle dilutes vinegar and slows down rate of reaction.


How to make invisible ink

invisible-writingLearn how to make invisible ink from household materials and start writing your secret messages and symbols. This is very interesting science experiment so you will get a lot of fun.

Method 1 – Using Lemon juice
two lemons

Required Materials

  • Lemon
  • Cotton swap
  • Light bulb


  1. Cut a lemon into two pieces and squeeze their juice into a cup
  2. Add few drops of water into lemon juice and mix it well.
  3. Dip a cotton swap into the mixture of water and juice and start writing your secret message on a white paper
  4. Allow your message to dry completely

When the paper dries the message will disappear. When it is time to show your message just heat the paper with light bulb by holding it over the bulb.


Method 2- Using Baking Soda

Required Materials

  • Baking Soda
  • Cotton swap or fountain pen
  • Grape Juice


  1. Put 2 spoonful of baking soda into the cup and pour warm water enough to make saturated solution.
  2. Dip the cotton swap (or use fountain pen) into the solution that you made and start writing message on white paper.
  3. When you finish writing your message let the paper dry until there is no sign of your message (you can dry it on sunlight).

When you want your message to be visible than dip any drawing brush into Grape juice and start painting it on your message