chemical reaction

chemical reaction

What is Chemical Reaction?

A 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

Facts

  • 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 bond of water - H2O

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

carbon-atomAn 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.

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. So, they need a way to complete their valence shell. For this reason, they form bond with other atoms.

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.oxygen-atom

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.

Example:

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.

Example:

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).

Facts

  • 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
Foamy Fountain

Foamy FountainYou may have seen the water fountains at many parks. These fountains give us very good view parks. So, let’s make this interesting fountain at home. This it will be colored and made of foam. We will call it the foamy fountain, and enjoy its beauty!

The foam that will be produced by the fountain is special because each bubble is filled with oxygen gas. You will also learn how this fountain works and what science is behind it.

Precaution: Always wear safety goggles and hand gloves when dealing with chemicals. Also, take the permission from your parents for the experiment, or involve them.

Things You Will Need

  • Empty plastic bottle about 500ml (half a liter) in volume
  • A half cup of Hydrogen Peroxide (20-volume or 6%)
  • 1 Tablespoon of Yeast
  • Liquid dish soap
  • Food coloring (Red, Green or any color)

How to Make

  1. Pour ½ cup of hydrogen peroxide in the bottle. Be careful! When dealing with hydrogen peroxide. It can irritate the skin, so it will be advisable to get the help of an adult.
  2. Add few drops of food coloring of your choice into the bottle.
  3. Add 1 tablespoonful of liquid dishwashing soap into the bottle.
  4. Close the bottle with cap, and shake it so that all the liquids mix together.
  5. Take a cup and add 3 to 4 tablespoons of water and 1 tablespoon of yeast in it.
  6. Stir the cup with a spoon to mix the water and yeast together.

Your fountain is ready!

When it is time to start fountain, just add water-yeast mixture into the bottle and BOOM!

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

What is Happening?

When you add the yeast into the bottle which contains the hydrogen peroxide, the breakdown of hydrogen peroxide takes place. The hydrogen peroxide is broken down into water and oxygen gas. The sudden release of oxygen in the bottle causes the bubbling. Because bottle contains liquid soap. These bubbles rush out of the bottle due to the formation of new bubbles. This will until the breakdown of hydrogen peroxide will take place.

Try It

  1. Increase the amount of yeast added to the bottle. Find out, does it affect the rate of reaction?
  2. Increase the amount of Hydrogen Peroxide and also add some water to the bottle. Find out, does it affect the timing of the fountain?
  3. What can you do to increase the height of the fountain? Think about it.
inflating balloon

inflating balloonInflating the balloon with vinegar and baking soda is a classic experiment. Perform this experiments with your friends, and explain to them what is happening? You won’t need to buy anything, all the materials you will find in your kitchen easily.

In this experiment, you will learn how the gas (carbon dioxide) produced from chemical reaction inflates the balloon.

Precaution: Always wear safety goggles and hand gloves when dealing with chemicals. Also, take the permission from your parents for the experiment, or involve them.

You Will Need

  • An empty plastic bottle
  • A Half-Cup of Vinegar
  • A Balloon
  • 2 to 3 Spoons of Baking Soda
  • Water

Procedure

  1. Pour the half cup of vinegar and one-fourth cup of water in the plastic bottle.
  2. Inflate and deflate the balloon with your mouth 2 times to make it lose.
  3. Pour 2 spoonful of baking soda into the balloon using a funnel (If you don’t have a funnel, you can make one from paper and scotch tape).
  4. 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

Your inflating balloon is ready!

When you want to inflate the balloon just hold the mouth of balloon tightly on the neck of the bottle. Then, let the baking soda in the balloon to fall in the bottle.

Now, observe the inflating balloon and chemical reaction.

What is Happening?

When the baking soda is added to vinegar, an acid-base reaction takes place. In this reaction, carbon dioxide gas is produced which develops pressure inside the bottle and starts to inflate the balloon. The balloon is being inflated with carbon dioxide gas, so it won’t float in the air. Because carbon dioxide is heavier gas than air.

Try It

If you want to slow down the reaction, so that balloon inflates slowly. Just, add water to the bottle to dilute the vinegar.

invisible-writing

invisible-writingDo you want to write some secret messages that no one can see without you? Learn how to make invisible ink from household materials, and start writing your secret messages and symbols. This is a very interesting science experiment, you will get a lot of fun.

Precaution: Always wear safety goggles and hand gloves when dealing with chemicals. Also, take the permission from your parents for the experiment, or involve them.

Method 1 – Using Lemon juice

two lemons

Things You Will Need

  • Lemon
  • Cotton swap
  • Light bulb

How to Make

  1. Cut a lemon into two pieces and squeeze their juice into a cup.
  2. Add few drops of water to the lemon juice, and mix it well.
  3. Dip a cotton swab into the mixture of water and juice. Then, 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 a light bulb by holding it over the bulb.

Method 2- Using Grape Juice and Baking Soda

Things You Will Need

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

How to Make

  1. Put 2 spoonfuls of baking soda into the cup.
  2. Pour some warm water into the cup. Then, stir well.
  3. Dip a cotton swab (or use a fountain pen) into the solution and start writing a message on a white paper.
  4. When you finish your writing, place the paper aside and let it dry until there is no sign of your message (you can dry it in sunlight).

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