Heat *

Question 1

Convection:

Fill the gaps:

• Convection occurs when ________ with a lot of ____ ______ in a ______ or ___ move and take the place of _______ with less ____ ______
• Eventually a __________ _______ is formed

Answer 1

• Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy
• eventually a convection current is formed

Question 2

Radiation:

Fill the gaps:

• _______ energy can be transferred by _________ waves
• this energy can transfer from a ___ object to the _____________
• if ______ than the __________, the object will _______ more radiation
• _________ surfaces can ____ and ______ different amounts of radiation

Answer 2

• thermal energy can be transferred by infrared waves
• this energy can transfer from a hot object to the surroundings
• if colder than the surroundings, the object will absorb more radiation
• different surfaces can emit and absorb different amounts of radiation

Question 3

Which surface absorbs the most radiation?

Answer 3

black, then shiny black

Question 4

Which surface absorbs the least radiation?

Answer 4

copper

Question 5

What is conduction?

Answer 5

the process of heat transfer through a material

Question 6

Conductors and insulators : Which conducts heat better?

• metal vs non-metal
• copper vs steel
• wood vs glass

Answer 6

• metal
• copper
• wood

Question 7

Why do metals conduct heat the best?

Answer 7

metals contain lots of free electrons, which move about randomly and hold the positive ions together
the collide with each other and the positive ions, conducting the heat through the metal

Question 8

How is heat conducted through a metal rod?

Fill the gaps:

• when a metal rod is heated at one end, the ____ _________ at the hot end gain _______ ______ and _____ ______
• these _________ _______ and _______ with other ____ _________ and _____ in the cooler part of the rod and transfer ______ _______ to these _________ and _____
• so the energy is transferred from the hot end to the cold end

Answer 8

• when a metal rod is heated at one end, the free electrons at the hot end gain kinetic energy and move faster
• these electrons diffuse and collide with other free electrons and ions in the cooler part of the rod and transfer kinetic energy to these electrons and atoms
• so the energy is transferred from the hot end to the cold end

Question 9

Why is fibre glass a good insulator?

Answer 9

it contains pockets of trapped air

Question 10

What is heat measured in?

Answer 10

Joules (J)