Question

heating curve for substance x. temperature (°c) -40 -20 0 20 40 time (min) 0 10 20 30 40 50 60 at approximately which temperature does a phase change begin? a -30°c b -10°c c 18°c d 0°c

Explanation:

Step1: Identify phase - change on graph

On a heating curve, a phase - change is indicated by a horizontal line where the temperature remains constant while heat is being added.

Step2: Read temperature at start of horizontal line

Looking at the graph, the horizontal line starts at approximately - 10°C.

Answer:

B. -10°C