Thermal physics

Question 1

What is gas pressure?

Answer 1

Collisions with gas particles and the walls of there container.

Question 2

How does gas pressure change?

via temperature

Answer 2

At constant volume, increase in temperature causes particles to have more kinetic energy. Increasing frequency and force of collisions.

Question 3

How does gas pressure change

via volume

Answer 3

At constant temperature, Decreasing volume increases pressure as there is less area for the particles to move without colliding with container walls.

Question 4

Explain solids thermal expansion

using kinetic particle model

Answer 4

Increase in temperature causes solids particles to vibrate faster taking more space. Limited by the strong attraction force of solids.

Question 5

Explain liquids thermal expansion

using kinetic particle model

Answer 5

Particles move faster around eachother. Limited by attraction force. (increase is greater than solids)

Question 6

Explain gases thermal expansion

using kinetic particle model

Answer 6

Volume will be size of container. If container is flexible, increasing temperature increases volume. Otherwise, increases pressure.

Question 7

Uses of thermal expansion?

Answer 7

1. 2 metal strips expand at different rates. This can be used to break a circuit with a heating element to control temperature
2. Expansion of liquids in thermometers

Question 8

What is evaporation?

Answer 8

When particles break away from liquids surface and form vapour

Question 9

How does this affect liquids temperature?

Relation to sweat?

Answer 9

Only particles high in kinetic energy leave the surface. This reduces the average energy of molecules in the liquid, reducing its temperature
Evaporation of sweat keeps body cool as, skin is in contact with an evaporating liquid.

Question 10

factors affecting evaporation

3 points

Answer 10

1. Higher temperature increases particles kinetic energy, allowing more particles to leave surface
2. Strong air flow across surface carries evaporating molecules away quickly
3. Increasing surface area increases evaporation

Question 11

What is thermal conduction?

(solids)

Answer 11

Atoms in lattice vibrate more as solid is heated. Attractive forces cause vibrations to be passed on to other atoms.

Question 12

Why are metals good conductors?

Answer 12

Metals contain sea of delocalised electrons which transfer thermal energy from the hot atoms to cold via colliding.

Question 13

Describe convection current?

Answer 13

Particles move faster when a fluid is heated, causing the heated particles to be less dense. They rise above the unheated denser particles in circulating motion.

Question 14

How to stop heat transfer via conduction/convection?

Answer 14

1. Place object in a vacuum.
2. Restrict movement of fluid

Question 15

How does radiation travel?

What is unique about this heat transfer method?

Answer 15

Via infrared rays
It can transfer heat through a vacuum

Question 16

What surfaces/tones are good emitters/absorbers of infrared radiation?

Answer 16

Dull and black surfaces

Question 17

What surfaces/tones are good reflectors of infrared radiation?

Answer 17

White and shiny surfaces

Question 18

How does earth gain energy?

How to greenhouse gases trap heat?

Answer 18

Earths energy comes from sun’s thermal radiation. The Earth also radiates thermal radiation into space. Determining the Earths temperature. Greenhouse gases absorb radiated heat from the Earth and disperse it in the atmosphere.