State the name given to the change of state labeled: (i) A (ii) B. Describe the movement of molecules in a gas. Which of the changes A, B or C is endothermic? Explain your answer.

Question 1:

a)

• (i) Change A is from liquid to gas.
  • A: Boiling (or Evaporation / Vaporisation)
• (ii) Change B is from liquid to solid.
  • B: Freezing (or Solidification)

b)
Molecules in a gas move randomly and rapidly in straight lines until they collide with other molecules or the container walls. They are far apart and have high kinetic energy.

c)
Change A is endothermic.

• Explanation: Endothermic processes absorb heat energy from the surroundings. Change A (liquid to gas) requires energy input to overcome intermolecular forces and allow molecules to escape into the gaseous state.

Question 2:

a)

• Apparatus: Bunsen burner

b)

• Apparatus: Volumetric flask

c)

• Apparatus: Liebig condenser

d)

• Apparatus: Desiccator

e)

• Apparatus: Pipette