Heat and Temperature

Question 1

power

Answer 1

the rate at which work is done

Question 2

electrical energy supplied

Answer 2

VIt

Question 3

mass =

Answer 3

density by volume

Question 4

why is it necessary to have a standard thermometer

Answer 4

if different thermometers which use different thermometric properties are used to measure the temperature change in a particular substance, they will most likely give different results

Question 5

what is the advantage of having that room temperature approximately halfway between the initial and final temperature of the water

Answer 5

heat energy lost to the surroundings at the initial stages of the experiment is approximately equal to the heat energy gained from the surroundings at the final stages of the experiment

Question 6

2 places of error in heat experiments

Answer 6

thermometer not sensitive enough

calorimeter not insulated (lagged)

Question 7

100 watts at 80% efficiency energy

Answer 7

100 J/s x .8 = 80 joules every second

Question 8

specific latent heat of vaporisation of water experiment, why was steam used?

Answer 8

the maths equation used is only based on steam and not liquid water being added to the cold water in the calorimeter

Question 9

specific latent heat of vaporisation of water experiment, how was the steam dried

Answer 9

the steam was insulated and sloped upwards to allow any condensation to fall back in the boiling tube
a steam trap could also be used

Question 10

why is a thermometer with low heat capacity more accurate?

Answer 10

such a thermometer would absorb less heat from system, the maths equation assumes that the thermometer absorbs no heat

Question 11

after you figure out using power how long it will take to heat water to a temperature, why will it actually take longer?

Answer 11

some of the electrical energy will be lost to the surrounding air (not all energy is used to heat water)

Question 12

2 precautions to minimise heat loss to surrounding air in heat experiments

Answer 12

lag calorimeter with polystyrene

insulate calorimeter

Question 13

experiment to measure specific latent heat of fusion of ice, why is warm water used 2

Answer 13

temperature rise of melted ice is greater (smaller % error)

can melt a larger mass of ice (smaller % error in weighing)

Question 14

the liquid in a vacuum-tube solar collector has a large specific heat of vaporisation, explain why

Answer 14

more energy is absorbed than released during the state of change

Question 15

describe in terms of heat transfer the operation of a heat pump

Answer 15

heat energy taken from a cold region making it colder and transferred to a hot region making it hotter

Question 16

give an advantage of a geothermal heating system over a solar heating system

Answer 16

a geothermal system works all of the time but a solar system only works when the sun is shining

Question 17

how is water cooled below room temperature

Answer 17

placed in the fridge for some time before the experiment

Question 18

heat capacity =

Answer 18

specific heat capacity x mass

Question 19

mechanical way of adding heat energy at a constant rate

Answer 19

water bath

Question 20

electrical way of adding heat energy at a constant rate

Answer 20

using a heating coil with a joulemeter and a rheostat

Question 21

if a calorimeter is made of polystyrene

Answer 21

may be ignored in the maths as it does not gain nor lose any heat

Question 22

give an advantage of using the kelvin as the SI unit of temperature

Answer 22

the values of temperature will always be positive

Question 23

2 characteristics of an accurate thermometer

Answer 23

small heat capacity

sensitive i.e. graduated to 0.1º C

Question 24

experiment to measure specific latent heat of fusion of ice

why was ice crushed and dried

Answer 24

. to ensure all ice was at 0ºC
. to ensure that only solid ice was added to the water and calorimeter and not a coating of liquid water on the surface of the ice

Question 25

how to crush ice

Answer 25

with a pestle and mortar

Question 26

how to dry ice

Answer 26

tissue paper was used to dry ice

Question 27

experiment to measure specific latent heat of fusion of ice

why would a very large amount of water make it less accurate

Answer 27

smaller change in temperature of water larger % error