2. Physical and Chemical Changes

Question 1

When does it matter change?

Answer 1

matter is said to undergo changes when energy is added or removed from the matter

Question 2

physical changes (2)

Answer 2

physical changes are those that do not change the fundamental structure of a substance i.e chemical composition is not altered

they are usually temporary, reversible and only the state of the substance changes

Question 3

chemical changes (2)

Answer 3

chemical changes are those in which the identity of the substance is altered, and it generally results in the formation of a new substance(s) i.e. chemical composition is altered

they are usually permanent, not easily reversible

Question 4

what are reversible and irreversible changes

Answer 4

reversible - changes which can be reversed (melting of ice and freezing of water)

irreversible - changes that cannot be reversed (baking of cake, cutting of fruits)

Question 5

what are slow and fast changes

Answer 5

slow changes - changes which occur very slowly (a seed growing into a tree)

fast changes - changes which occur very rapidly (lightning, blinking of an eye)

Question 6

what are periodic and non-periodic changes

Answer 6

periodic changes - changes which occur periodically or at fixed, regular intervals (change of seasons, pendulum)

nonperiodic changes - changes which do not occur periodically or happen at random (sneezing, change of weather)

Question 7

what are desirable and non-desirable changes

Answer 7

desirable changes - changes which produce useful results (can be brought about by man or nature)

undesirable changes - changes which produce useless or harmful results (can be brought about by man or nature)

Question 8

4 main points of physical changes

Answer 8

• Unaltered composition
• temporary (generally)
• no change in mass because no matter is added or removed
• not marked by evolution or absorption of heat

Question 9

4 main points of chemical changes

Answer 9

• altered composition
• permanent change (generally)
• change in mass of the reactant because matter is added/removed, but total mass stays the same
• accompanied by evolution/absorption of heat or even sometimes evolution of light

Question 10

6 examples of physical changes

Answer 10

• melting of wax
• boiling of milk
• rain cycle
• ringing of an electric bell
• heating a platinum wire
• magnetization of iron

Question 11

6 examples of chemical changes

Answer 11

• carbon cycle
• Rotting of eggs
• formation of iron sulfide when iron and sulfur powder are heated
• rusting of iron
• addition of iron to acid
• Baking of a cake

Question 12

40/40 PLEASEEEE

Answer 12

YESSSIRR