P1.1 Enegry Transfer by Heating Processes

Question 1

What is heat radiation?

Answer 1

The transfer of heat energy by infrared radiation

Question 2

What is IR emitted/absorbed by?

Answer 2

All objects are continually emitting and absorbing IR, it is emitted from the surface of an object

Question 3

How does temperature affect the rate infrared transfer?

Answer 3

An object that’s hotter than its surroundings emits more IR than it absorbs (as it cools down), an object that is cooler than its surrounding absorbs more heat than it emits (as it warms up)

Question 4

How does the surface colour and texture of an object affect the rate infrared transfer?

Answer 4

Dark, matt surfaces absorb more and emit more IR than light, shiny surfaces which reflect a lot of the IR falling on them

Question 5

What can light, shiny surfaces be used for?

Answer 5

Because they reflect IR, they can reduce the amount of energy transferred by radiation

Question 6

What are the three states of matter?

Answer 6

Solid, liquid and gas

Question 7

What makes a substance a particular state?

Answer 7

The particles are the same, the arrangement and energy of the particles are different

Question 8

Describe the structure of a solid

Answer 8

Fixed, regular arrangement - the particles don’t have much energy so they can only vibrate about their fixed position

Question 9

What is the bonding like in a solid?

Answer 9

Strong forces of attraction hold the particles together

Question 10

Describe the structure of a liquid

Answer 10

The particles are close together, but can move past each other and form irregular arrangements

Question 11

What is the bonding like in a liquid?

Answer 11

There are weaker forces of attraction between particles than those in solids

Question 12

Describe the structure of a gas

Answer 12

The particles have more energy than those in a liquid/solid, and are able to freely move around in random directions at high speeds

Question 13

Why do solids melt, and liquids boil?

Answer 13

Because when you heat a substance you give its particles more kinetic energy so they vibrate or move faster

Question 14

Describe the melting of a solid

Answer 14

The particles gain enough energy to be able to move past each other

Question 15

Why can gases and liquids flow, but solids can’t?

Answer 15

Because liquid and gas particles can move past each other, whereas solid particles are in a fixed position

Question 16

Why are gases compressible and solids/liquids aren’t?

Answer 16

Because when you compress a gas you’re just reducing the distance between the particles and bringing them closer together, solids and liquids can’t really get much closer

Question 17

What is conduction?

Answer 17

When you heat particles in solids, they vibrate more and collide with neighbouring particles and share pass on some of their extra energy

Question 18

If you were to heat one side of a solid, why does the other side also gradually get hot?

Answer 18

Due to conduction, the energy is gradually passed all the way through the solid to the other side and increases the amount of heat radiating from the solid’s surface

Question 19

What affects the rate of conduction?

Answer 19

The density of the substance, the denser a substance, the closer the particles which means the particles collide more often

Question 20

Why are metals such good conductors?

Answer 20

At the hot end, delocalised electrons in the metal gain kinetic energy and move freely through the substance quicker - they then collide with other DE and pass on the energy and so on and so on.

Question 21

Why do metals conduct heat so much quicker than other substances?

Answer 21

Because transferring heat by electrons freely moving throughout the substance, is much faster than particles slowly passing on energy to neighbour atoms

Question 22

When does convention occur?

Answer 22

When more energetic particles in gases or liquids move from a hotter region to a cooler region - and take their heat energy with them

Question 23

Immersion heaters, heater coils…

Answer 23

Heat the water at the bottom of the tank by conduction, these particles then get more energy and move around faster. They move around faster so there is more space between them (the water becomes less dense) - this then results in the less dense water rising above the denser (cooler) water. The colder water sinks towards to the heater coils and rises - and so it goes on

Question 24

Immersion heaters, what happens to the particles at the bottom of the tank?

Answer 24

They move around faster so there is more space between them (the water becomes less dense) - this then results in the less dense water rising above the denser (cooler) water.

Question 25

Immersion heaters, when hot water rises…

Answer 25

The colder water sinks towards to the heater coils and rises - and so it goes on

Question 26

What ends up happening in an immersion heater?

Answer 26

Convection currents going up, round and down, circulating the heat energy around the water