This document discusses different types of changes of state that substances undergo: melting (solid to liquid), vaporization (liquid to gas), freezing (liquid to solid), condensation (gas to liquid), and sublimation (solid to gas). Examples are given for each type of change. Melting occurs when ice cubes turn to water with heat transfer. Vaporization can be boiling or evaporation, with boiling converting liquid to vapor with heating and evaporation extracting salt from sea water slowly at the liquid surface. Freezing happens when liquid water cools and freezes into ice cubes. Condensation cools gas into liquid like water vapor into clouds. Sublimation directly changes solid into gas like burning camphor or dry

1. CHANGES AROUND
US
STD 7
LEVEL-1
R.SANGEETHA
1122119BD138

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What happens when you heat butter?
Ice melts on heating. Which state
does it change to?
What are the three states of matter?
What are physical and chemical
properties of a substance?

3. CHANGES AROUND US
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Changes takes place around us all
the time.
Change - alternation in the
composition of matter, மா ற
Examples of change: melting of ice,
heating of water and rusting of iron.

4. CHANGE OF STATE
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Change of state of a substance is one
of the major physical changes we
encounter in our lives.
Definition: The process of changing of a
substance from one physical state to
another at a definite temperature is
known as change of state.

6. CHANGES OF STATE
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Melting- solid to liquid
Vaporization- liquid to gas
Freezing- liquid to solid
Condensation- gas to liquid
Sublimation- solid to gas

7. MELTING
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The change of solid state into
liquid state by means of heat
transfer.
Eg: ice cubes in room temperature
will turn into water.

8. VAPORIZATION
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Two types- boiling and evaporation.
Boiling- conversion of a liquid into
vapours on heating.
Evaporation- technique used to
extract salt from sea water. It is a
slow process. Takes place at the
surface of liquid.

9. FREEZING
• Particles loose energy on
cooling and hence they
experience strong force of
attraction. Hence water (liquid)
freezes to form ice cubes
(solid).

10. CONDENSATION
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Cooling down of gas.
Conversion of gas into liquid
by cooling.
It is a Physical change.
Eg:water vapour condenses
to form clouds.

11. Sublimation
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Solid is directly converted
into gas.
Eg: burning of camphor,
napthalene balls, dry ice etc.