Page 213 - New Medley 5 Semester 2

 change where no new substance is formed.

 change where properties and composition of the substance remain the same.

Chemical Changes

When the food is cooked, it is not possible to
get back the raw food material. When a paper

is burnt, we get its ash. Can we get the paper
back from the ash? Such a change where the

original substance cannot be obtained from
the nal product is called a chemical change.

When substances burn, they combine with Burning of an incense stick

oxygen and new substances are formed. When is a chemical change.
a candle burns, carbon dioxide, water vapour and carbon are produced.

us, a chemical change is a:

 permanent and irreversible change.

 change where a new substance is formed.

 change where the properties and composition of substance do not remain

the same and the new substances formed are completely di erent from the
original one.
2 • Problem Solving

Circle the odd one out.
1. Carbon, Carbon dioxide, Nitrogen, Iron
2. Ocean water, Milk, Air, Nitrogen

3. Rusting of a lock, Milk turning into cheese, Mixing salt into water, Baking a cake

4. Freezing of water, Cutting paper, Burning petrol, Stretching of spring

AT ONE GO

 All matter is made up of atoms and molecules.

 Atoms are very tiny particles that cannot be seen with the naked eye.
 Elements are made up of identical atoms whereas compounds are made up of two or more elements.
 A physical change is temporary and reversible whereas a chemical change is permanent and

irreversible.

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