Question

classify each of the following as a physical change or property, or a chemical change or property.
a) a fireplace poker glows red when you heat it in the fire.
b) a marshmallow turns black when toasted too long in a campfire.
c) hydrogen peroxide dental strips will make your teeth whiter.
d) if you wash your jeans with chlorine bleach, they will fade.
e) if you spill some nail polish remover on your skin, it will evaporate quickly.
f) when making ice cream at home, salt is added to lower the temperature of the ice being used to freeze the mixture.
g) a hair clog in your bathroom sink drain can be cleared with drain cleaner.
h) the perfume your boyfriend gave you for your birthday smells like flowers.

Explanation:

To solve this, we need to recall the definitions:

• Physical change: No new substance formed (e.g., phase change, color change without reaction).
• Chemical change: New substance formed (e.g., burning, reaction).
• Physical property: Observable without changing substance (e.g., color, smell).
• Chemical property: Describes ability to react (e.g., reactivity with other substances).

Part (a)

A fireplace poker glows red when heated.

• This is a physical change (no new substance; just temperature-induced color change, like metal heating).

Part (b)

A marshmallow turns black when toasted too long.

• Toasting causes combustion (new substances like carbon form) → chemical change.

Part (c)

Hydrogen peroxide dental strips whiten teeth.

• H₂O₂ reacts with stains (new substances) → chemical change (reaction occurs).

Part (d)

Washing jeans with chlorine bleach fades color.

• Bleach reacts with dye (new substances) → chemical change (reaction to remove color).

Part (e)

Nail polish remover evaporates quickly.

• Evaporation is phase change (liquid → gas, no new substance) → physical change.

Part (f)

Salt lowers ice cream mixture’s freezing point.

• This is a physical property (describes ability to affect freezing point, no reaction occurs here; it’s a colligative property).

Part (g)

Drain cleaner clears hair clogs.

• Drain cleaner (e.g., lye) reacts with hair (new substances) → chemical change (reaction to break down hair).

Part (h)

Perfume smells like flowers.

• Smell is an observable property (no reaction) → physical property.

Final Answers:

a) Physical Change
b) Chemical Change
c) Chemical Change
d) Chemical Change
e) Physical Change
f) Physical Property
g) Chemical Change
h) Physical Property

Answer:

To solve this, we need to recall the definitions:

• Physical change: No new substance formed (e.g., phase change, color change without reaction).
• Chemical change: New substance formed (e.g., burning, reaction).
• Physical property: Observable without changing substance (e.g., color, smell).
• Chemical property: Describes ability to react (e.g., reactivity with other substances).

Part (a)

A fireplace poker glows red when heated.

• This is a physical change (no new substance; just temperature-induced color change, like metal heating).

Part (b)

A marshmallow turns black when toasted too long.

• Toasting causes combustion (new substances like carbon form) → chemical change.

Part (c)

Hydrogen peroxide dental strips whiten teeth.

• H₂O₂ reacts with stains (new substances) → chemical change (reaction occurs).

Part (d)

Washing jeans with chlorine bleach fades color.

• Bleach reacts with dye (new substances) → chemical change (reaction to remove color).

Part (e)

Nail polish remover evaporates quickly.

• Evaporation is phase change (liquid → gas, no new substance) → physical change.

Part (f)

Salt lowers ice cream mixture’s freezing point.

• This is a physical property (describes ability to affect freezing point, no reaction occurs here; it’s a colligative property).

Part (g)

Drain cleaner clears hair clogs.

• Drain cleaner (e.g., lye) reacts with hair (new substances) → chemical change (reaction to break down hair).

Part (h)

Perfume smells like flowers.

• Smell is an observable property (no reaction) → physical property.

Final Answers:

a) Physical Change
b) Chemical Change
c) Chemical Change
d) Chemical Change
e) Physical Change
f) Physical Property
g) Chemical Change
h) Physical Property