Physics Module 4

Question 1

What is thermal energy?

Answer 1

The total kinetic and potential energies of all the particles in a material

Question 2

What is thermal expansion?

Answer 2

Particles taking up more space as they vibrate faster, and expanding the material.

Question 3

What state of matter experiences the most thermal expansion, and why?

Answer 3

Gas expands the most because of the strength of attraction between particles. Solids have strong bonds, liquids have weak bonds, and gases have no bonds.

Question 4

Do gases only expand when heated?

Answer 4

No. Volume depends on the container, so if temperature increases in a fixed volume, pressure will increase.

Question 5

What is conduction?

Answer 5

When thermal energy is transferred from one part of material to another. When heated, particles move faster, pushing on other particles and speeding them up too.

Question 6

What materials conduct heat best/worst and why?

Answer 6

• Metals are best because atoms are close together, and because free electrons collide with atoms and make them vibrate faster.
• Gases are worst because the molecules are far apart (which makes them good insulators).

Question 7

What is convection?

Answer 7

Heat transferred through the movements of liquids of gases in convection currents.

Question 8

How are convection current formed?

Answer 8

Warmer areas of the fluid expand and become less dense, so it rises as cooler, denser fluid sinks and displaces it.

Question 9

What is thermal radiation?

Answer 9

Thermal energy transferred through electromagnetic waves, usually infrared, but sometimes visible light too.

Question 10

What is the difference between boiling and evaporation?

Answer 10

• Evaporation is when a liquid below its boiling point changes into a gas.
• Boiling is when the vapour pressure in water bubbles is strong enough to overcome atmospheric pressure.

Question 11

What is specific heat capacity?

Answer 11

The amount of energy that must be transferred to heat 1kg of a specific material by 1C.

Question 12

What is the formula for specific heat capacity?

Answer 12

Energy transferred = mass x specific heat capacity x temperature change

Question 13

What is thermal capacity?

Answer 13

The amount of energy that must be transferred to heat a specific mass of a specific material by 1C.

Question 14

What is the formula for thermal capacity?

Answer 14

Thermal capacity = mass x specific heat capacity

Question 15

How does temperature change in melting ice and boiling water?

Answer 15

It reaches the melting/boiling point, then does not change, even as it absorbs more thermal energy.

Question 16

What is latent heat of fusion?

Answer 16

The extra thermal energy used to separate particles in a melting solid so it can form a liquid, instead of increasing the solid’s temperature above the melting point.

Question 17

What is latent heat of vaporisation?

Answer 17

The extra thermal energy used to separate particles in a boiling liquid so it can form a gas, instead of increasing the liquid’s temperature above the boiling point.

Question 18

What is the formula for latent heat?

Answer 18

Energy transferred = mass x specific latent heat