Thermal Physics Flashcards
What is room temperature
25 degrees Celsius
What is absolute zero
-273 Celsius or 0K
Describe the compressibility of a liquid
The liquid itself is not compressible, rather the air in between
What is evidence for the kinetic molecular model of matter
The random motion of particles in suspension. Ie. Brownian motion which can be described in terms of molecular bombardment
What is specific latent heat
The amount of energy required to change the state of 1kg of a material without changing its temperature
What is boiling point determined by
The atmospheric pressure
Describe the difference between boiling and evaporating
Boiling occurs only at boiling point, throughout the liquid and the rate is dependent on the heat supply
Evaporation occurs at the surface of the liquid,through a range of temperatures and the rate depends on humidity, surface area and air movement above the surface
Are pressure and volume inversely or directly proportionate
Inversely
What happens to the potential energy as particles move further apart
It increases
Consequences of thermal expansion (3)
Railway lines and cement and buildings buckle unless they have expansion joints.
Hot water pipes would break if they didn’t have an expansion joint in the form of a loop
Expansion in a pendulum during warm weather slows the clock (thus they have adjusting screws)
Application of thermal expansion
Bimetallic strips. Two strips of metal, often copper and iron. When heated copper expands more than iron causing the iron strip to bend with copper on the outside
Switches in electrical circuits
Distinguishing properties of solids (4)
Incompressible
Keep their shape
Cannot flow
High density
Distinguishing properties of liquids (4)
Incompressible
Take shape of bottom of container
Flow
High density
Distinguishing properties of gas
Compressible
Fill volume of container
Flow
Low density
Particle structure of solids in terms of arrangement, separation and motion of the particles
Vibrate around a fixed/central position and do not swap positions as there are strong forces between molecules. The particles are arranged in a lattice and there is minimal space between particles
Particle structure of liquid in terms of arrangement, separation and motion of the particles
Fluid shape (takes shape of container)
Particles are close together, so have a fixed volume and can only be compressed slightly
Particles are loosely packed together and irregularly arranged
Liquid particles can move randomly in any direction, provided the particles stay close to one another - they can vibrate and slide over each other
Particle structure of gas in terms of arrangement, separation and motion of the particles
Randomly arrangement, unrestricted by each other so have completely random motion in any and all directions .
Relationship between motion of particles and temperature
Average kinetic energy is related to temperature, meaning the higher the temperature, the more kinetic energy and the more, quicker movement of particles. Particles have the least movement at 0K / -273*C
Boyle’s law
Pressure and volume of a gas
The less volume the more collisions between the particles and the wall of the containers. When they collide they exert a force meaning more collisions = more force causing pressure to increase
PRESSURE OF GAS IS INVERSELY PROPORTIONAL TO VOLUME
Evidence for the kinetic particle model of matter
Random motion of particular in a suspension. This (brownian) motion seen in dust + pollen is explained in terms of random molecular bombardment, massive particles moved by light, fast moving molecules of air.
What affects the properties of solids, liquids and gases
Forces, distances between particles (atoms, molecules, ions and electrons) and the motion of particles
How may microscopic particles be moved
Through collisions with light fast-moving molecules
Internal energy
Sum of potential and kinetic energies of the particles (atoms/molecules/ions) of a body. Thermal energy transferred to/from a body results in a change in internal energy. More distance means more potential energy
What does the amount of expansion of solids/liquids/gases depend on
The strength of the bonds between particles and the temperature increase
Expansion in solids
When heated, kinetic energy increases causing particles to vibrate faster and over a larger distance. Forces the particles exert on each other overcome the forces of the bonds, forcing them further apart (expansion). This distancing is minimal as the bonds are very strong
Expansion in liquids
More than in solids as the forces of cohesion are weaker
Expansion in gases
Forces are very small, resulting in a lot of expansion as the molecules are able to move faster at higher temperatures, increasing the magnitude of the forces during collisions
Describe an increase in temperature of an object
An increase in the average kinetic energies of all the particles in the object
What causes the cooling of a liquid
Evaporation
Specific heat capacity
Amount of energy required to raise the temperature of 1kg of a substance by 1*C
Unit of specific heat capacity
J kg-1 C-1
J kg-1 K-1
Experiment to find specific heat capacity of metal
Place immersion heater into central hole at top of block
Place thermometer into smaller hole with oil to ensure thermometer is surrounded by hot metal
Fully insulate the block by loosely wrapping with cotton wool
Record temperature
Connect heater to power supply and turn off after 10 minutes, then record the highest temperature it reaches as it cools
Melting and boiling
Energy input without change in temperature
When does condensation occur
When gas molecules in the air lose their kinetic energy as they collide with a cool surface. They become closer and form bonds to become a liquid
Factors that affect evaporation (3)
Temperature
Surface area
Air movement
Cooling of an object in contact with an evaporating liquid
As the liquid cools, the solid does too. Used in fridges and air conditioning units
Temperature
The average kinetic energy of molecules in a substance
Conduction in non-metal
Transfer of heat through vibration of atoms with nearby atoms
Describe experiments to demonstrate the properties of good and bad conductors of heat.
Take rods of different materials with the same dimensions (same length and cross-sectional area), and attach a drawing pin to the end of each using the same mass of wax.
Using a container with four rubber-lined holes in the side. Insert the rods through the holes, pushing them in the same amount. Fill the container with boiling water and start the stopwatch. Time how long it takes the drawing pin to fall off each rod and compare the times. The rod that allowed the pin to fall off fastest is the best conductor.
Thermal conduction in metals
The transfer of heat due to vibration of atoms with nearby atoms and free moving electrons which heat farther atoms
Convection
The transfer of heat in liquids and gases
Best emitter and absorber of infrared rays
Dull black
Worst emitter and absorber of infrared rays
Shiny white
Radiation
Infrared waves emitted from the surface of all objects that, the rate of emission increases as the surface temperature increases and this method of thermal energy transfer does not require a medium
what happens to an object if the rate at which it receives energy is less or more than the rate at which it transfers energy away from the object
If it is less, then the temperature of the object will cool down
More, it will increase
What needs to happen for an object to be at a constant temperature
it needs to transfer energy away from the object at the same rate that it receives energy
how is the temperature of the Earth affected
by factors controlling the balance between incoming radiation and radiation emitted from the Earth’s surface
Everyday consequences of thermal conduction, convection and radiation (3)
Handle of a pan getting hot
Metal roof of a house getting hot
Rubber soles melting next to a radiator
Everyday applications of conduction, convection and radiation (3)
Heating kitchen pans to cook with
Heating a room by convection
Refrigerators
Greenhouses
Explain some of the complex applications and consequences of conduction, convection and radiation where more than one type of thermal energy transfer is significant (2)
Radiator in a car
A fire burning wood or coal
