Question

21 The heating curve of a substance is shown below. 2.1.1 2.1.2 2.1.3 2.1.4 2.1.5 graph 100 (b) 100 10 10 Time (minutes) Write down the physical state of the substance at t= 15 minutes. What is the boiling point of the substance? 25 (13) S (Write down only INCREASE, DECREASE or REMAINS THE SAME.) Refer to the Kinetic Molecular Theory to fully explain the answer to QUESTION 2.1.6 Define the term boiling point (2) 1.7 Name the process that takes place between 5 minutes and 11 minutes (1) 18 Name the process that takes place between 19,5 minutes and 24 minutes (1) [14]​

Answer 1

2.1.1 Liquid (The line is in the sloped region indicating the substance is in the liquid state)

2.1.2 100 °C (The temperature levels off at 100 °C, indicating this is the boiling point)

2.1.3 REMAINS THE SAME (As energy is added, the temperature remains the same during boiling)

2.1.4 Boiling point is the temperature at which the vapor pressure of the liquid equals the external pressure and the liquid begins to boil.

2.1.5 Evaporation (constant slope indicates evaporation where particles gain enough energy to escape the liquid)

2.1.6 Boiling: As heat is added, the particles gain enough kinetic energy to overcome the intermolecular forces holding them in the liquid. The particles break free from the surface and enter the gas phase, causing the temperature to remain constant at the boiling point.

2.1.7 Evaporation

2.1.8 Vapourization (steam/vapor is produced)