Heat and Phase Changes of Water

The video explains the process of adding heat to water at its boiling point, leading to vaporization without a temperature increase. It introduces the concept of latent heat of vaporization, which is the energy required to convert liquid to gas. Example calculations demonstrate how to determine the heat needed for vaporizing different masses of water. Once fully vaporized, additional heat increases the temperature of the water vapor.

What happens to water when it reaches its boiling point and more heat is added?

• The temperature increases.

• The water starts to freeze.

• The water begins to vaporize.

• The water remains in liquid form.

What phase change occurs when water reaches its boiling point and heat is added?

• Solid to liquid

• Solid to gas

• Liquid to gas

• Gas to liquid

Why does the temperature of water remain constant at the boiling point even when heat is added?

• The heat is used to cool the water.

• The heat is used to increase the pressure.

• The heat is used to vaporize the liquid.

• The heat is lost to the surroundings.

What is the latent heat of vaporization?

• The heat required to vaporize a liquid into gas.

• The heat required to increase the temperature of a liquid.

• The heat required to freeze a liquid.

• The heat required to melt a solid.

How much heat is required to fully vaporize 5 grams of water if the latent heat of vaporization is 1000 J/g?

• 1000 joules

• 3000 joules

• 5000 joules

• 2000 joules

If 1 gram of water requires 1000 joules to vaporize, how much heat is needed for 3 grams?

• 1000 joules

• 4000 joules

• 2000 joules

• 3000 joules

What is the relationship between the mass of water and the heat required to vaporize it?

• The heat required decreases with mass.

• The heat required is the same for all masses.

• The heat required increases with mass.

• The heat required is independent of mass.

If the latent heat of vaporization is 1000 J/g, how much heat is needed to vaporize 2 grams of water?

• 1000 joules

• 4000 joules

• 2000 joules

• 3000 joules

What happens to the temperature of water vapor when more heat is added after it has fully vaporized?

• The temperature decreases.

• The temperature remains constant.

• The temperature increases.

• The water vapor condenses.

Why does adding more heat to water vapor increase its temperature?

• Because the heat is lost to the surroundings.

• Because the heat is used to freeze the vapor.

• Because there are no other phases beyond gas.

• Because the heat is used to vaporize more liquid.