section 4 - energy

Question 1

what is conduction? (definition)

Answer 1

conduction is the transfer of thermal energy through a substance by the collision and vibration of the atoms within the substance

Question 2

When a substance is heated, the molecules gain lots of k______ e________

Answer 2

kinetic energy

Question 3

The more kinetic energy the molecules have, the more they are v_____________.

Answer 3

vibrating

Question 4

Vibrating molecules c__________ into adjacent ones, t_____ k_______ e__________ from one molecule to the next

Answer 4

• collide
• transferring kinetic energy

Question 5

Based on the above information, which materials transfer energy by conduction most effectively - solids, liquids or gases?

Answer 5

solids

Question 6

Why can thermal energy not be transferred by conduction through a vacuum?

Answer 6

No particles in a vacuum to pass the heat along

Question 7

Why do metals make the very best conductors, compared to non-metals?

Answer 7

Because they have compact particles unlike non metals

Question 8

Air is a gas, and therefore a b________ conductor

Answer 8

bad

Question 9

Our clothes trap a layer of air against our bodies, and this layer of t___________ a______ prevents thermal energy being transferred a__________ from our bodies by conduction to the surroundings.

Animal’s fur or feathers trap i______________ layers of air around their bodies in the same way. Both the trapped air and the fur itself are both b______ c_________ (good insulators).

Answer 9

1. trapped air
2. away
3. insulating
4. bad conductors

Question 10

what is convection? (definition)

Answer 10

Convection is the transfer of heat through fluids ( liquids and gases ) by the upward movement of warmer, less dense regions of fluid

Question 11

Which state of matter does convection not occur in? Why?

Answer 11

solids because the molecules are tightly packed together but for convection to take place the molecules should be free to move like liquids and gases

Question 12

Why can convection also not happen in a vacuum?

Answer 12

a vacuum has no presence of particles

Question 13

Why does trapping air in small pockets also help to reduce the amount of thermal energy transferred by convection?

Answer 13

because it is trapped, convection currents cannot be set up easily

Question 14

We said previously that having a layer of fur or wearing a puffer jacket, reduces the amount of h_____ l_______ to the surroundings by conduction because both air and fur are b_________ c___________

Answer 14

1. heat loss
2. bad condectors

Question 15

fur also helps prevent heat loss by c_______________

Answer 15

convection

Question 16

w_____ a_____ i______ t_______ in small pockets ________________, and so ____________ cannot form around the hot object.

Answer 16

1. when air is trapped
2. it cannot move around
3. convection currents

Question 17

what is thermal radiation?

Answer 17

the transfer of thermal energy by infra-red (IR) waves