physical and chemical changes

2. 1. Concept of a physical and a chemical change.
2. Investigate the observable changes during a physical and a
chemical change
3. Conservation of mass during a physical and chemical change.
4.Concept of matter & the changes in states of matter.
5. Differences between a physical and chemical change.
6. Effects of chemical change on physical properties of substances.
7. Understanding the terms crystallization, galvanization, rusting,
fermentation, sublimation etc. with examples.
8. Significance of chemical changes in everyday

3. We notice different changes around us
.
We can classify these changes into
1 Physical changes – Occur when the
appearance of substance changes but
chemically the substance is the same.
No new substance is produced
2.Chemical changes- Occur when
chemical reactions occur & new
substances are produced

4. Cut a piece of paper in
four square pieces . Cut
each square piece into
four square pieces. Lay
these pieces on the table
so as to get the original
piece of paper
 Can you Join them to
make them as original
piece of paper ?
 Is there any change in
the property of the
paper ?

5.  Square Pieces OR Triangular Pieces
pieces

6. Activities :3&4
• Crush a small piece of
chalk into dust.
• Add little water to the dust
to make a paste. Roll it
into the shape of a piece
of chalk.
• Let it dry.
• Did you get back chalk
from the dust?
• Take some ice in a plastic
tumbler. Melt a small portion of
ice . Now place the tumbler in
the Fridge / freezing mixture
( ICE PLUS COMMON SALT )
• Does water become solid
again? (Salt reduces the freezing
point of water, so allows ice to
attain temp. lower than O 0C)
EXPT::
https://www.youtube.com/watch?feature=
player_detailpage&v=xKDYcX2fRYo

7.  Boil some water in a
container.
 And observe
 Hold an inverted pan by
its handle over the steam
at some distance from
the boiling water .
 Again observe the inner
surface of the pan.
 Do you see any droplets
of water there ?

8. ACTIVITY :6&7
1. Gems or pebbles to be
used to show particles
arrangement in solids,
liquids and gases.
2. Three groups of
students to act as
1. SOLIDS ,
2. LIQUIDS ,
3. GASES
GROUP ACTIVITY

9. Change of State
Remember
The particles in a solid are close together and
vibrate.
The particles in a liquid are further apart and
slide over each other.
The particles in a gas are far apart and bump
into each other as they move quickly.

10. ACTIVITY-9
 Hold a used hack-saw blade with a pair of tongs.
 Keep the tip of the free end on the flame of a stove or candle
 Wait for a few minutes .
 Observe change in color of the tip of blade after heating and
cooling .
 Make a note of changes observed.

11. * A physical change is a change during which no new
substance is formed.
** Physical changes occur when the state of a substance
changes ( SOLID LIQID GAS )
*** Physical change occurs when a substance is crushed, ground
or cut into smaller pieces.
**** Physical changes are often easy to reverse.
Physical Changes ReversibleChanges)

12. PHYSICAL CHANGES
* Properties such as Shape. Size. Colour
and State of a substance are called its
PHYSICAL Properties
**A Change in which a substance
undergoes a change in its Physical
Properties is called a PHYSICAL
CHANGE.
***A Physical change is generally
REVERSIBLE.
**** In such a change no new substance
is produced
We can use our senses to see

13. 10. How do you use these materials to show or explain
Physical changes
1. BALLOON
2. RUBBER BAND
3. CANDLE
4. APPLE
5. SALT AND WATER
6. SUGAR AND WATER
7. MODELLING CLAY / DOUGH
8. SPRING

14. Concept / MIND MAP
through

17. Chemical Changes
A chemical change or chemical reaction occurs
whenever a new substance forms.
Evidence that a new substance is formed are –
a change in colour.
a gas given off.
a new solid forms.
a change in temperature.

18. The following are examples of chemical change.
• Wood burns
• An egg is cooked to become a white and yellow solid.
• A metal panel on a car rusts.
• Fireworks explode.
• Concrete hardens.
• An egg cooks.
• Paper burns.

19. Chemical Change
Rusting nails as new substance is produced

20. Chemical Change
Effervescent tablet

21. Chemical Change
Reaction of Vinegar and Baking soda releases
CO2 which turns lime water milky

22. Chemical Change
Burning wood

23. Burning of Magnesium Ribbon
Magnesium burns with oxygen to form Magnesium oxide which dissolves
in water to form magnesium hydroxide which turns blue litmus red

24. Reaction of Copper sulphate with Iron
Copper sulphate reacts with iron to form Iron Suphate
( Green) and Copper ( Brown deposit )

25. TERMS & Meanings
Galvanization Definition:
Galvanization is a process
that applies a coat of zinc to
metal to prevent oxidation.
Example: Galvanized nails
at a hardware store.
crystallization is the slow precipitation of
crystals from a solution of a substance.
Crystallization can also refer to the solid-
liquid separation and purification
technique in which mass transfer occurs
from the liquid solution to a pure solid
crystalline phase.

26. Questions
Classify the following examples as physical or chemical changes.
a) Water freezes to make snow.
b) A cake cooking.
c) Food is digested.
d) A puddle of water evaporates.
e) Lighting the gas in a bunsen burner.
f) Lighting a match.
g) Steam condensing on a mirror.
h) Melting a gold nugget to make a gold bar.
i) Dynamite exploding.
j) Burning your toast.
k) Water freezes to make ice cubes.
l) Ice cream melting.
m) Iron rusting
a) Physical
b) Chemical
c) Chemical
d) Physical
e) Chemical
f) Chemical
g) Physical
h) Physical
j) Chemical
i) Chemical
k) Physical
l) Physical
m) Chemical