Lessons 17-20

Question 1

how does heat or thermal energy flow?

Answer 1

always high temperature to low temperature

Question 2

define heat

Answer 2

it is the energy that you add or remove

Question 3

define temperature

Answer 3

it is a measure of kinetic energy within the subject

Question 4

whats the first thing that happens once something is heated?

Answer 4

the particles are given energy- kinetic- which makes them move around faster.

Question 5

whats the second thing that happens once something is heated, after the particles are given kinetic energy?

Answer 5

the particles get potential energy as they move further apart. this is why objects expand when they get hot.

Question 6

state the three ways of heat transfer

Answer 6

conduction, convection and radiation

Question 7

explain conduction

Answer 7

process of heat transfer through vibrating particles. occurs mostly in solids where particles are touching.

Question 8

what makes metals such good conductors?

Answer 8

Metals are good conductors cause the kinetic energy can be passed though delocalised electrons, which move through the substance freely. The structure of metal is a lattice which has overlapping elements. The more electrons in the lattice, the better the conductor it is.

Question 9

explain convection

Answer 9

it occurs in liquids and gasses.

When a substance is heated, the particles move faster and and the fluid substance expands, making it less dense. As it is less dense, it rises.

As the substance rises away from the heat source, it cools and the particles fall back down as they become less dense.

The circulation of particles is called a convection current.

Question 10

explain radiation

Answer 10

this type of heat transfer does not involve particles, instead energy is transferred as electromagnetic waves.

This frequency produces infrared waves.

Question 11

how is heat from the sun transferred?

Answer 11

infrared radiation (does not need particles or can travel in vacuum)

Question 12

what kind of colour is a bad absorber/emitter of heat?

Answer 12

light colours, eg white.

Question 13

what kind of colour is a good absorber/emitter of heat?

Answer 13

dark colours eg black.

Question 14

best kind of surface to absorb heat?

Answer 14

black matte. matte absorbs heat well.

Question 15

best kind of surface to reflect heat?

Answer 15

black shiny. shiny surfaces are great reflectors.