09 Thermal Properties of Matter

What is internal energy

The sum of internal kinetic energy and the internal potential energy of an object

Describe a heating curve as the temperature increases

As the temperature of the particles increase, the average kinetic energy of the particles increase. The substance undergoes thermal expansion. Some of the energy transferred to the substance does work against the attractive forces between particles. The average separation between the particles increases.

Describe a heating curve as the substance changes state

As the temperature of the particles remains constant, average kinetic energy of the particles remains constant. As the substance changes state, all the energy transferred ti the substance does work against thr attractive forces between the particles. The average separation between the particles increases.

Describe a cooling curve as the temperature descreases

As the temperature of the particles decrease, average kinetic energy of the particles decreases. The substance undergoes thermal contraction, some energy is transferred out of the substance. The particles become less able to overcome the attractive forces between them. The average separation between the particles decreases.

Describe a cooling curve as the substance changes state

As the temperature of the particles remains constant, the average kinetic energy of the particles remains constant. As the substance changes state, energy is transferred out of the substance. as the particles become less able to overcome the forces of attracion between them, the average separation of the particles decreases.

What is heat capacity?

The change in internal energy of an object per unit change in its temperature

What is specific heat capacity?

The change in internal energy of an object per unit mass for each unit change in its temperature.

Formula for heat capacity

Q = CT

What is latent heat

The amount of energy transferred to change the state of a substance at a constant temperature

What is specific latent heat

The amount of energy transferred per unit mass of a substance to change the state of a substance at a constant temperature.

Why is lv higher than lf?

When a substance changes from a liquid to a gas, the average separation between particles increases at a greater amount than when the substance changes from a solid to a loquid. When the substance changes from a liqudi to a gas, more energy is transferred to the substance to do work against attractive forces between the particles.

Why would a jet of steam hurt more than boiling water at the same temperature?

Although they have the same kinetic energy, the jet of steam has more internal potential energy because the average separation between the steam particles is larger.

How does pressure affect evaporation

The greater the average force exerted per unit area on the liquid surface by the colliding air molecules, the less quickly particles escape from the liquid to the surrounding air.

How does temperature affect evaporation

The particles have a greater kinetic energy. More particles will have enough energy to overcome the attractive forced by other liquid particles.

How does the surface ares affect evaporation

The greater the number of particles escaping the liquid to the surrounding air per unit time.

How does wind speed affect evaporation

The greater the rate if removal or particles that have just escape to the air.

How does the boiling point affect evaporation

The lower the boiling point, the higher the rate of evaporation

How does humidty affect evaporation

The lower the humidity, the lower the concentration of water vapour in the air.

What is evaporation

Evaporation occurs when faster particles at the liquid surface with enough energy to overcome the forces of attraction by other liquid particles to escape into the air

How is boiling different from evaporation

Vaporisation occurs throughout the liquid and is faster

Boiling occurs at the boiling point whole evaporation occurs between the melting and boiling point

The temperature remains the same for boiling, descreases for evaporation

Boiling needs a heat source