P1: Thermal Physics Flashcards
Evaporation
It is the escape of the more energetic particles and occurs constantly on the surface of liquids
Thermistor thermometer
It contains a material that becomes a better electrical conductor when the temperature rises (semi-conductor). So when temperature increases, a higher current flows from a battery, causing a higher reading on the meter
Liquid in glass thermometer
In this thermometer, As temperature rises or falls, the liquid (mercury or alcohol) expands or contracts. Amount of expansion can be matched to temperature on a scale.
Thermocouple thermometer
In this thermometer, The probe contains 2 different metals joined metals to form 2 junctions. The temperature difference causes a tiny voltage which makes a current flow. A greater temperature difference gives a greater current. Thermocouple thermometers are used for high temperatures
Sensitivity
The change occurring on a scale with respect to the physical change of the quantity measured.
Range
The interval between the upper and lower fixed points on any scale
Linearity
When intervals on a scale is the same throughout.
Responsiveness
How long it takes for the thermometer to react to a change in temperature
Melting point
This is when a solid turns into a liquid. Temperature increases thus kinetic energy in solid increases and particles vibrate more rapidly but there is no increase in temperature of the substance when melting because thermal energy supplied is instead being used to overcome the forces of attraction between particles of the solid thus turning it into a liquid
Boiling point
This is when a liquid turns into a gas. Energy is supplied thus internal kinetic energy of the molecules in the liquid increases and particles vibrate more rapidly but there is no increase in temperature of the substance
Latent Heat of Fusion
This is the heat needed to change a mass of 1 kg the substance from a solid at its melting point into liquid at the same temperature
Condensation
Is when a gas turns back into a liquid
Solidification
The change of a liquid or gas to solid
Insulators
Are used to reduce the amount of heat lost to the surroundings
Conduction
Is the flow of heat through
Convection
Is the flow of heat through a fluid from places of higher temperature in places of lower temperature by movement of the fluid itself
Radiation
Is the flow of heat from one place to another by means of electromagnetic waves
Thermal radiation
Is mainly infra-red waves, but very hot objects also give out light waves. Infra-red radiation is part of the electromagnetic spectrum
Emitter
Sends out thermal radiation
Reflector
Reflects thermal radiation, therefore is a bad absorber
Solar panel
The sun’s thermal radiation is absorbed by a matt black surface and warms up the pipes containing water
Kelvin
Temperature scale based on average kinetic energy of particles. Lowest possible temperature is 0 K.
Celsius
Temperature scale based on freezing and boiling points of water.
kinetic particle model
All matter is made atoms in constant motion.
Solid
Particles vibrate, and are held in position by strong attractive and repulsive forces.
Liquid
Particles have more freedom to move than those in a solid.
Gas
Particles are in constant random motion.
Heat
Thermal energy that is transferred from one substance to another.
Kinetic energy
Energy that particles have due to their motion.
Potential energy
Energy stored due to an object’s position or arrangement
Internal Energy
The total of all kinetic and potential energy of every particle in a substance.
Kelvin-Celsius conversion
0 K= -273 ℃ or 0 ℃ = 273 K
Absolute zero (0 K)
The temperature of a substance in which the kinetic energy of all particles is zero.
Specific heat capacity (c)
the amount of energy required to raise the temperature of 1 kg of a substance by 1 K.
Latent Heat
Energy required to completely change the phase (state) of a substance.
Vaporisation
Change of phase from liquid to gas that occurs at the boiling point of the liquid.
Thermal conductor
A material that transfers thermal energy easily.
Thermal Insulator
A material that does not transfer thermal energy easily.
Convection
Method of heat transfer that involves convection currents.
Radiation
Transfer of energy (electromagnetic radiation) without the movement of any particles.
Greenhouse Effect
Incoming solar radiation warms the earth.
Enhanced Greenhouse Effect
Additional warming of the Earth due to extra greenhouse gases in the atmosphere (put there by human activity).
When a solid is heated, the particles of the solid
vibrate
The best material for absorbing infra-red radiation
black, matt
The best material for emitting infra-red radiation is
black, matt
The best material for reflecting infra-red radiation is
light, shiny
The worst material for absorbing and emitting infra-red radiation is
light, shiny
Objects that emit the most infra-red radiation have
higher temperatures
Metals contain these and they make them better conductors of heat
free electrons
Efficiency
percentage of energy that is transferred usefully
Wasted energy
dissipates and heats up the surroundings
Rate of heating or cooling can be increased by
Greater surface area, darker, duller surfaces, using conductors not insulators, greater temperature difference
During condensation particles
transfer energy to the surface, and move closer together
Particles with strongest forces
solid
Particles with weakest forces
gas
Radiation
when heat travels as invisible infra-red waves
What is *thermal* energy?
Another phrase for *internal* energy
Molecules within a solid
-Held to each other by *electrostatic forces* (due to electrical charges of sub-atomic molecules)
Heating a solid
-Heat energy supplied *increases kinetic energy* of the molecules
Effect of increasing internal energy on the molecules
Increases their *kinetic* and/or *potential* energy associated with *random motion* and their *position*
Specific heat capacity of a substance (c) definition
*Energy* needed to raise temp. of *unit mass* of the substance by *1K* *without* change of state
Measurement of the *specific heat capacity* of a metal
Block (known mass) of metal in *insulated container*
Measurement of the *specific heat capacity* of a liquid
Known mass of liquid in *insulated calorimeter*
Latent heat of fusion
Energy needed to change the state of a *solid* to a liquid (and vice versa) *without* change of temperature
Latent heat vaporisation
Energy needed to change the state of a *liquid* to a gas (and vice versa) *without* change of temperature
*Specific* latent heat of fusion
Energy needed to change the state of a *solid* of *UNIT MASS* to a liquid (and vice versa) *without* change of temperature
*Specific* latent heat of vaporisation
Energy needed to change the state of a *liquid* of *UNIT MASS* to a gas (and vice versa) *without* change of temperature
Latent heat equation
Q = ml (l is specific latent heat of fusion/vaporisation)
What is Charles Law?
The Volume of a fixed mass of gas is directly proportional to its temperature in kelvin if the pressure is kept constant
What is Boyles law?
The volume of a fixed mass of gas is inversely proportional to its pressure if the temperature is kept Constant
PV =constant
P1V1 = P2V2
What is the Pressure law?
The pressure of a fixed mass of gas is directly proportional to the temperature in kelvin when the volume is kept constant
