Matter Chemical Changes: Explanation and Example

Introduction: 

Matter is anything that has mass and occupies space. Matter cannot always be seen. Whatever is in our surroundings is made up of ‘matter.’ All matters are made up of tiny particles, such as atoms, molecules, or ions.  

Whatever the change is seen around are either physical change or chemical change. 

In this chapter we are going to learn about ‘chemical change.’ 

Explanation: 

Chemical change: 

Matter can change its state. In matter two different types of changes are observed— physical change and chemical change. 

A chemical change is when a new substance is formed. 

When there is change in shape, color and size it is known as chemical change. 

Light and heat, formation of gas, change in color are the signs of chemical change. 

Activities-1 

A burning log goes through a chemical change. The log starts off as solid wood. When you set the log on fire, it changes chemically.  

Carbon dioxide gas and ash form. The properties of these substances are very different from those of wood.  

That is because they are made up of different combinations of elements. 

 Activity-2 

Look closely at some pennies.  

Take salt water and add 150 milliliters of vinegar. Stir until the salt and vinegar dissolves. 

Dip a penny halfway into the liquid. Keep it for some time. Then remove the penny. 

Compare the half you held with the half that was in the liquid. 

When a substance is undergoing chemical change, we can consider it as a chemical reaction. 

Real life examples of chemical change  

Baking of cakes: 

When you bake a cake, the ingredients go through a chemical change. They form new substances.  

The properties of the substance formed (the cake) are entirely different from the properties of its ingredients.  

That is why the baked cake has a taste that differs from eggs, milk, and flour. 

Ripening of Fruits: 

When we expose a bunch of bananas to the air for a few hours, it slowly changes its color and results in the spoiling of bananas.  

This is because the gas present in the air (O₂) reacts with particles present in the banana. When it is exposed for a long time, the substance breaks down into a new substance. 

When this happens, food may change color or have a bad smell.