Page 20 - ICSE Chemistry 8

Freezing: The process of change of a liquid into its solid state on cooling is called freezing.
Mel ng: The process of change of a solid into its liquid state at a fi xed temperature is called mel ng.

Condensa on: The process of change of a gas into its liquid state is called condensa on.

Sublima on: The process of change of a solid to its gaseous state directly without changing into a liquid
state is known as sublima on.

Deposi on: The process of change of a substance from gaseous state to its solid state directly without
changing into a liquid state is called deposi on.

Activity 1.1

Aim: To observe change when ice melts
Materials required: A glass beaker, some ice cubes, thermometer

Procedure

• Take some ice cubes in a glass beaker.

• Note the temperature of the ice every minute using a thermometer
thermometer.

• Draw a temperature- me graph on a graph paper. ice cubes
• Note your observa ons in a table.

Observa on: As the temperature increases the ice starts to
melt and eventually changes into liquid state.

LAW OF CONSERVATION OF MASS

The law of conserva on of mass states that mass can neither be created nor destroyed. The mass of a
substance remains the same during a change. The density of ma er and the volume occupied by the ma er
may vary within a system but the mass remains constant. The law of conserva on of mass holds because
the naturally occurring elements are stable. The
atom is also neither created nor destroyed.
Know Your Scientist
The substances may show change in size, shape,
Antoine Lavoisier, in the late 18th century,
kine c energy and other proper es during
rediscovered the Law of Conserva on of
a physical change but the total mass of the
Mass. He describes the law as a fundamental
substances remains the same. principle of Physics.

Let’s understand the law of conserva on of mass
with the help of some examples.

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