1. Name the type of chemical reaction which occurs in the following reactions.
(a) AB + CD -> AD + BC
(g) Acid + Base - Salt + Water
2. Stainless steel spoons are not used in pickle jars. Why?
3. What type of changes does burning of candle involve? Explain.
4. Classify the following as physical or chemical change.
E Think An
(b) A + 2D AD2-heat
(d) ABA+B
(f) A + BC-AC + B
(c) A + 2BAB2 + heat
(e) A + B AB
(b) Cooking of food
(d) Beating of gold into the foil
(1) Photosynthesis in plant
(a) Condensation of steam
(c) Ripening of fruit
(e) Burning of kerosene oil
Physical and Chemical Chan
Answers
Answer:
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Explanation:
Question 1:
Which of these is a chemical change?
(a) A substacne with different chemical properties is formed.
(b) A substance in a different state but similar chemical properties is formed.
(c) The molecules of the substances do not undergo any change.
(d) A substance with a different shape and size but similar chemical properties is formed.
ANSWER:
(a) A substance with different chemical properties is formed.
A chemical change occurs when two substances react chemically to form new substances with different chemical properties.
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Question 2:
Which of these is an irreversible physical change?
(a) rusting of iron
(b) freezing of water
(c) a double decomposition reaction
(d) breaking of a glass tumbler
ANSWER:
(d) breaking of a glass tumbler
Breaking of a glass tumbler is an irreversible physical change. Rusting of iron is a chemical change. Freezing of water is a reversible physical change. A double decomposition reaction is a chemical change.
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Question 3:
An arrow pointing downwards in a chemical reaction shows
(a) evolution of gas
(b) formation of precipitae
(c) oxidation
(d) displacement
ANSWER:
(b) formation of precipitate
In a chemical reaction, an arrow pointing downwards shows the formation of a precipitate and an arrow pointing upwards shows the evolution of a gas.