Heat and Temperature Flashcards
(27 cards)
power
the rate at which work is done
electrical energy supplied
VIt
mass =
density by volume
why is it necessary to have a standard thermometer
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
what is the advantage of having that room temperature approximately halfway between the initial and final temperature of the water
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
2 places of error in heat experiments
thermometer not sensitive enough
calorimeter not insulated (lagged)
100 watts at 80% efficiency energy
100 J/s x .8 = 80 joules every second
specific latent heat of vaporisation of water experiment, why was steam used?
the maths equation used is only based on steam and not liquid water being added to the cold water in the calorimeter
specific latent heat of vaporisation of water experiment, how was the steam dried
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
why is a thermometer with low heat capacity more accurate?
such a thermometer would absorb less heat from system, the maths equation assumes that the thermometer absorbs no heat
after you figure out using power how long it will take to heat water to a temperature, why will it actually take longer?
some of the electrical energy will be lost to the surrounding air (not all energy is used to heat water)
2 precautions to minimise heat loss to surrounding air in heat experiments
lag calorimeter with polystyrene
insulate calorimeter
experiment to measure specific latent heat of fusion of ice, why is warm water used 2
temperature rise of melted ice is greater (smaller % error)
can melt a larger mass of ice (smaller % error in weighing)
the liquid in a vacuum-tube solar collector has a large specific heat of vaporisation, explain why
more energy is absorbed than released during the state of change
describe in terms of heat transfer the operation of a heat pump
heat energy taken from a cold region making it colder and transferred to a hot region making it hotter
give an advantage of a geothermal heating system over a solar heating system
a geothermal system works all of the time but a solar system only works when the sun is shining
how is water cooled below room temperature
placed in the fridge for some time before the experiment
heat capacity =
specific heat capacity x mass
mechanical way of adding heat energy at a constant rate
water bath
electrical way of adding heat energy at a constant rate
using a heating coil with a joulemeter and a rheostat
if a calorimeter is made of polystyrene
may be ignored in the maths as it does not gain nor lose any heat
give an advantage of using the kelvin as the SI unit of temperature
the values of temperature will always be positive
2 characteristics of an accurate thermometer
small heat capacity
sensitive i.e. graduated to 0.1º C
experiment to measure specific latent heat of fusion of ice
why was ice crushed and dried
. 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
