KBSM SCIENCE FORM 4 CHAPTER 5 5.1

1. SCIENCE FORM 4
CHAPTER 5:
ENERGY AND
CHEMICAL
CHANGES

2. 5.1 PHYSICAL AND
CHEMICAL CHANGES
•There are two types of changes:
(i) Physical changes
(Ii) Chemical changes
-

3. PHYSICAL CHANGES
- Affects the physical properties
of a substance, such as its size,
shape and state.
- Usually reversible.
- No new substance is formed.

4. EXAMPLES INVOLVING
PHYSICAL CHANGES:
(a) Melting of ice
(b) Evaporation of water
(c) Dissolving sugar in water
(d) Crystallisation of sodium chloride
from its saturated solution
(e) Heating of iodine crystals
https://www.youtube.com/watch?v=jX9pskb
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5. 5.1 PHYSICAL AND CHEMICAL CHANGES
Melting of ice Evaporation of water

6. 5.1 PHYSICAL AND CHEMICAL CHANGES
Dissolving of
sugar in water
Heating iodine
crystals

7. (II) CHEMICAL CHANGE
- Produces new substances that have
properties different from those of the
original substance.
- Usually irreversible.
- Examples: Burning of papers

8. (B) COLOUR OF A PEELED APPLE
CHANGES WHEN IT IS EXPOSED
TO AIR

9. (C) FRYING AN EGG

10. (D) COMBUSTION OF FUEL

11. (e) When iron filings are heated with sulphur
powder, the mixture glows brightly. A
black solid, iron sulphide is formed.
Iron + Sulphur Iron sulphide

13. (f) When magnesium ribbon is heated,
it burns with a bright flame. A white solid,
magnesium oxide is formed.
Magnesium + Oxygen Magnesium oxide

14. (g) Zinc reacts with blue copper sulphate
solution to form a colourless zinc
sulphate solution and brown copper.
Zinc + Copper sulphate Zinc sulphate
+ Copper
(h) Iron nail rust when water and oxygen are
present. Rust is brown.
Iron + Oxygen + Water Rust

15. CHEMICAL CHANGES
Reaction of zinc with copper
sulphate solution

16. (i) Heating green copper carbonate
produces black copper oxide and
releases carbon dioxide.
Copper carbonate Copper oxide +
Carbon dioxide
(j) Mixing potassium iodide and lead nitrate
solution forms lead iodide, a yellow
precipitate.
Potassium + Lead Potassium + Lead
iodide nitrate nitrate iodide

17. SCIENCE MODULE P.96

37. CHAPTER 5: ENERGY AND CHEMICAL CHANGES QUIZ
1. Which of the following involve chemical
changes?
I. Lighting a match
II. Hard-boiling an egg
III. Melting tin to cast tin bars
A. I and II
B. I and III
C. II and III
D. I, II and III

38. CHAPTER 5: ENERGY AND CHEMICAL
CHANGES QUIZ
2. Which of the following statements about a
chemical which undergoes physical changes is not
true?
A. Its size is changed
B. Its state is changed
C. Its shape is changed
D. Its chemical properties are changed

39. CHAPTER 5: ENERGY AND CHEMICAL
CHANGES QUIZ
3. Why does the temperature rise in a chemical reaction?
A. The reaction is fast
B. The reaction is slow
C. The reaction absorbs heat energy
D. The reaction releases heat energy