Question

the horizontal lines on a cooling curve represent:
i. a temperature change
ii. a constant temperature
iii. a change of state
i and ii
i alone
ii alone
ii and iii

Explanation:

A cooling curve shows the temperature change of a substance over time as it cools. During a change of state (e.g., from liquid to solid), the temperature remains constant. Horizontal lines on a cooling curve indicate a constant temperature (II) which occurs during a change of state (III). A temperature change (I) would be represented by a non - horizontal (sloped) line on the cooling curve.

Answer:

II and III