Flashcards
Unit 6: Thermal physics
Flashcards do conjunto (24)
- 1Recall that substances expand when heatedthermal expansion = increase of length of a solid or increase of volume of a liquid or a gas due to an increase of temperature
- 2Recall that gases expand much more than solids and liquidsGases expand much more than solids and liquids
- 3Describe applications and some consequences of thermal expansionExpansion gaps - used in buildings, bridges and railway tracks to allow for themal expansion. Without them, e.g. bridges would buckle.
Steel tyres - fitted on train wheels by heating the tyre so it expands, then fitting it on the wheel. As the tyre cools, it contracts so it fits very tightly on the wheel.
Bimetallic strips - consists of 2 different metals such as brass and steel stuck together. When the temperature of the strip rises, one metal expands more than the other so the strip bends. - used in fire alarm and thermostats. - 4Describe the fixed points for the Celsuis scale of temperatureice point (0 degrees C)
steam point (100 degrees C) - 5Explain how a liquid-in-glass thermometer worksa thermometer that uses the expansion of a liquid (usually mercury) as its thermometric property.
thermometric property = physical property of a themometer that varies with temperature - 6Explain how a thermocouple thermometer worksan electrical thermometer that makes use of the voltage between 2 different metals in contact with each other.
- 7Describe applications of the use of each type of thermometer aboveliquid-in-glass thermometer:
at home, in the office, in greenhouses, in hospitals
thermocouple thermometer:
in ovens, temperature variation of gas flow, data logging, remote locations - 8Describe the thermal expansion of a gas at constant pressurethe volume of a gas at constant pressure increases when its temperature is increased
- 9Explain what is meant by the range, sensitivity and linearity of a thermometerrange = the range of temperatures that can be measured from the lowest to the highest.
sensitivity = change of the thermometric property for a 1 degree C rise of temperature.
linearity = the extent of the difference between the readings of a thermometer and the readings of a standard gas thermometer - 10Explain what is meant by thermal capacitythe energy needed by an object to raise its temperature by 1 degree C
- 11Describe an experiment to measure the specific heat capacity of a body and recall and use the equation E=mc (02 - 01)specific heat capacity = energy needed by a 1kg of a substance to raise its temperature by 1 degree C.
- 12Describe what is meant by melting point and boiling point and recall that energy is needed to melt a solid or boil a liquidmelting point = the temperature at which a substance melts or solidifies.
boiling point = the temperature at which a substance boils or condenses.
Energy is needed to melt a solid or boil a liquid. - 13Explain the difference between boiling and evaporationBoiling occurs throughout a liquid at its boiling point.
Evaporation occurs from the surface of a liquid when its temperature is below the boiling point. - 14Explain what is meant by latent heat of fusion and of vaporisationlatent heat of fusion = energy supplied to a substance to melt it; also, energy removed from a substance to solidify or freeze it.
latent heat of vaporisation = energy supplied to a liquid substance to vaporise it; also, energy removed from a vapour to liquefy it. - 15State what is meant by specific latent heat of fusion and of vaporisation and recall the use of the equation E=mlspecific latent heat of fusion = energy needed to melt a 1kg of a substance at its melting point; also equal to the energy that must be removed from 1kg of a substance at its melting point to solidify it.
specific latent heat of vaporisation = energy needed to vaporise 1kg of a substance at its boiling point; also equal to the energy that must be removed from 1kg of a vapour to liquefy it at its boiling point. - 16Describe experiments to compare the thermal conduction of different materials
- 17Explain why metals are good conductors of heat and non-metals are poor conductorsConduction in a metal is due to free electrons transferring energy inside the metal.
Non-metals are poor conductors because they do not contain free electrons. - 18Recall that convection happens due to density changes when a gas or a liquid is heatedConvection only takes place in fluids (i.e. a gas or a liquid). It happens due to circulation (convection) currents within the substance. Heating a liquid or a gas makes it less dense. Convection currents transfer thermal energy from the hotter parts to the cooler parts.
- 19Describe and explain experiments and applications that show or use convectionHot water at home:
Hot water from the boiler rises and flows into the tank where it rises to the top. This is where you draw hot water from when you use the hot water tap.
Hot air balloon:
- carries its own burner to heat the air in the balloon - this makes the air in the balloon less dense than the surrounding air. So the balloon rises and floats. - 20Recall the main branches of the spectrum of electromagnetic radiationRadio waves, Microwaves, Visible light, Infra-red, Ultraviolet rays, X-rays
- 21Understand that all objects emit infra-red radiation which increases with increasing temperatureAll objects emit infra-red radiation. The hotter an object is, the more infra-red radiation it emits. If an object is very hot, it emits light as well.
The radiation emitted by an object due to its temperature is sometimes called thermal radiation. - 22Describe experiments that show the properties of good and bad emitters and absorbers of infra-red radiationDark, matt surfaces are better emitters and absorbers of infra-red radiation than light, shiny surfaces
- 23Recall the main methods of increasing heat transfer to stop devices from over-heatingHeat transfer to or from an object can be increased by increasing the surface area of the object or making its surface matt black.
- 24Recall the main methods of reducing heat transfer to keep objects warmHeat transfer in cold weather from a building can be reduced using aluminium foil behind radiators, cavity wall insulation, double glazing and loft insulation.
Heat transfer in summer into a building can be reduced by painting outdoor surfaces white, using white window shutters or blinds, and having thick walls.
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- GCSE Physics (Unit 6: Thermal physics) FlashCards sobre Unit 6: Thermal physics, criado por cmharrisuk em 09-04-2015.
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