P1.1 Energy Transfer by Heating Flashcards
How does sublimation happen?
Sublimation is the change of state between a solid and a gas, an example of this is dry ice. This happens because it gains thermal energy which transfers into kinetic energy turning it into a gas.
What objects emit heat radiation?
Anything above 0 degrees K
Describe the arrangement of particles in a solid.
Close together in a regular pattern.
Describe the arrangement of particles in a liquid.
Close together and random.
Describe the arrangement of particles in a gas.
Far apart and random.
Describe the movement of particles in a solid.
Vibrate about a fixed position.
Describe the movement of particles in a liquid.
Move around each other.
Describe the movement of particles in a gas.
Move around quickly in any direction.
State four different transfers of energy.
Conduction, convection, evaporation and condensation.
Give two examples of convection.
Immersion heater.
Radiator.
Give an example of evaporation.
Sweating
Give an example of conduction.
A saucepan on a hob.
What two things are dark, matt surfaces good at?
Absorbing infrared radiation.
Emitting infrared radiation.
State the three things at which the rate of an object transferring energy by heating depends on.
Surface area and volume.
The material from which the object is made.
The nature of the surface it is contacting.
How do you calculate specific heat capacity?
m x c x feta
Why are steel electric kettles often made very shiny?
because shiny surfaces are poor emitters therefore they lose less heat by radiation.
The hotter a surface is the more…?
radiation it radiates
what happens in terms of particles when a solid melts into a liquid?
particles will gain more kinetic energy. They will vibrate more and move faster to eventually overcome the strong forces of attraction that hold the particles in a solid together.
how do the change in particles energy cause a convection current in a room?
The particles have more energy so the distance between them becomes greater therefore the air expands and becomes less dense. This reduction in density means the hot air rises above the cooler denser air.
what factor would increase the rate of the evaporation of a liquid?
The liquid has a high temperature low density large surface area or low concentration
factors that increase the rate of condensation of gas?
The temperature of the surface the gas touches is lower or if the surface area of the surface the gas touches is larger.
what for features of a vacuum flask reduces heat transfers?
shiny surface - reduce radiation
plastic stopper - reduces conduction
Vacuum gap between walls of bottle - reduce convection
why do the hairs on your skin stand up when you are cold?
to trap insulating air around your body to limit the amount of heat lost by convection.
why do some people skin go pink when they are hot?
The body diverts more blood to flow near the surface of the skin so that more heat can be lost by radiation.
why would an arctic animals have small ears?
to minimise heat loss by radiation and stay warm.
how could we insulate our house?
loft installation, double glazing, cavity wall insulation, thicker curtains.
how does cavity wall insulation work?
it reduces heat transfer by convection because pockets of air are trapped in the foam.
how does loft insulation work?
reduces heat transfer by conduction.
how do you calculate payback time?
initial cost Divided by annual saving
what is meant by a U-value?
they measure how effective a material is as an insulator
what is meant by specific heat capacity?
The amount of energy needed to raise the temperature of 1 kg of a substance by 1°.
how do work out specific heat capacity?
Energy transferred (J) = mass (kg) X specific heat capacity (J/kg) X temperature change (‘c)
what does convection take place in?
liquids & gases
why can can’t convection take place in solids?
because the particles cannot move
