Page 129 - Active Science 5 Ebook and Activity

1. Physical Change: A change in the physical state of matter is called a physical
change. The change of ice (a solid) into water (a liquid) and the further change of

water into vapour (a gas) is an example of physical change.

Water vapour (gas) can be changed into liquid by cooling. Liquid matter can be
changed back into ice (solid) by freezing. Such changes are called physical changes.
A physical change is temporary and reversible. It does not change the basic atomic
structure of the substance.

ice water steam

2. Chemical Change: When a paper is burnt, we Factual Study
get ash but we cannot get the paper back from The starting and ending materials of

the ash, such a change is called a chemical a physical change are the same, even
change. When a substance burns, it combines though they may look different. For
with oxygen and a new substance is produced. example, melting of wax is a physical
The rusting of a nail, the cooking of eggs, etc., change. From wax, we prepare candle
and from a candle, we get wax (after
are other examples of chemical changes.
burning).

Let’s Recapitulate

Choose the correct option.
1. The process of changing liquid to a gaseous form is called _____________.

a. melting b. evaporation c. condensation
2. The process of changing solid into a liquid form is called ______________.
a. evaporation b. condensation c. melting

3. When we cool a liquid, the movement of molecules _____________.
a. slows down b. becomes faster c. stops

4. A _____________ change makes a new substance altogether.
a. physical b. mechanical c. chemical

A chemical change makes a new substance altogether. A chemical reaction is accompanied
by emission of light, heat, colour change, gas production or sound.

LET’S
REVISE

• Anything that occupies space and has weight is called matter.
• Matter is made up of atoms and molecules.

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