revision unit 13

Question 1

explain why metal are good conductors of energy

Answer 1

metal have free electrons, so once one side of the metal is heated the electrons would gain kinetic energy and would diffuse to the other side and hit the other electrons making go faster heat would be transferred

Question 2

what is convection

Answer 2

it is circulation of a fluid once it is heated

Question 3

why do fluids raise

Answer 3

once a fluid is heated the particles get further away lower the density because the mass now occupies a bigger volume so it would rise up

Question 4

what are the examples of convection

Answer 4

1. sea breezes when hot air goes up and cold air would replace it
2. in hot water at home, where the hot water would go up and the cold would go down

Question 5

what is evaporation

Answer 5

it is the process where particles in liquids leaves below its boiling points at the surface

Question 6

why does evaporations causes a cooling effect

Answer 6

the particles in liquids have week intermolecular forces so the particles with faster kinetic energy would break from the other liquids molecule once they leave the liquid would have less kinetic energy making it cooler

Question 7

the rate of evaporation can be increased by?

Answer 7

1. increasing the surface area
2. increasing the temperature
3. creating a draught of air across the surface of a liquid

Question 8

how can you increase the rate of condensation

Answer 8

1. increasing the surface area

2. reducing surface temperature

Question 9

the higher the temperature of an object….

Answer 9

the more infrared radiation it emits in given times, and the shorter the wavelength the more intense the radiation is

Question 10

what does the sun emit

Answer 10

the sun emits all types of electromagnetic radiation which most of them are blocked by the ozone layer

Question 11

what is the greenhouse effect

Answer 11

so in a green house the infrared radiation from the sun would go into the greenhouse and get trapped by the glass keeping it warm, the same idea applies when greenhouse gases cause global warming

Question 12

which surfaces are the best emitters of radiation

Answer 12

dark mat surfaces emit for infrared radiation than light, shiny surfaces

Question 13

which surfaces are best at absorbing and reflecting radiation

Answer 13

light shiny surfaces would absorb less and reflect more than dark surfaces

Question 14

what are the factors that effect the rate of energy

Answer 14

1. the temperature difference between the objects and its surrounding
2. the material the object is made from
3. the mass of the object
4. the surface and volume of the object
5. the nature of surface that came in contact with the object

Question 15

what is expansion of heating

Answer 15

the expanding of an substance due to increase in temperature, where gasses expand more than liquids

Question 16

what are examples of expansion of heat in gases and liquid

Answer 16

1. a radiator thermostat, when a oil is heated in would expand causing the valve to be open allowing hot water to flow to the radiator
2. liquid in a glass thermometer, where the liquid would expand because of the heat coming from the someone and it would land on there temperature

Question 17

what are examples of uses of expansion of solids

Answer 17

1. expansion gaps are used in building to avoid them to become buckle in the summer
2. we would heat a tyre and fit on a train wheel so when it cools down and contracts it would fit tightly
3. bimetallic strips that are used in thermostats to