physic chapter 9 Flashcards
When a material is heated at constant pressure
- Its temperature increases
- Its overall volume increases (it expands)
- Its density decreases
why does expansion happen
- The molecules start to move around (or vibrate) faster as they gain kinetic energy
- This causes them to collide with each other more often and push each other apart
explain why solids expand slightly
The low energy molecules cannot overcome the intermolecular forces of attraction holding them together
by how much does the solid expand
Expands slightly
why do solids, liquids and gases expand by different amounts
This behaviour is influenced by the distances and strength of the forces between particles in each state
by how much does the liquid expand
Expands more than solids
explain why liquids expand more than solids
The molecules have enough energy to partially overcome the intermolecular forces of attraction holding them together
by how much does the gas expand
Expand significantly
why does the gas expand significantly
The high energy molecules have enough energy to completely overcome the intermolecular forces of attraction holding them together
what are the applications of thermal expansion
- Liquid-in-glass thermometers
- Temperature-activated switches
what are the consequences of thermal expansion
The expansion of solid materials can cause them to buckle if they get too hot
these may include, railway lines, bridges and shrink fitting
what is the internal energy
the internal energy of a substance is the total energy of all its particles
what affects the temperature of a substance
- the mass of the substance
- type of material
- amount of energy transferred to a thermal store
define specific heat capacity
the amount of thermal energy required to raise the temperature of a unit mass of substance by 1 degrees celsius
how can we calculate the specific heat capacity
thermal energy required / temperature change x mass of a substance
what are some of the commonly used units to measure the specific heat capacity
joule per kilogram per degree celsius ( J/Kg * C)
how is specific heat capacity determined
- Place the beaker on the digital balance and press ‘zero’
- Add approximately 250 ml of water and record the mass of the water using the digital balance
- Place the immersion heater and thermometer in the water
- Connect up the circuit as shown in the diagram, with the ammeter in series with the power supply and immersion heater, and the voltmeter in parallel with the immersion heater
- Record the initial temperature of the water at time 0 s
- Turn on the power supply, set it at approximately 10 V, and start the stopwatch
- Record the voltage from the voltmeter and the current from the ammeter
- Continue to record the temperature, voltage and current every 60 seconds for 10 minutes
- Repeat steps 2-8, replacing the beaker of water for the solid block of aluminium and starting with recording its mass using the digital balance
how can we calculate the specific heat capacity of the aluminium
change in thermal energy = average current x average potential difference x time spent heating
the melting and boiling points are also known as
the fixed point
at which temperature does the pure water boil
100 degrees celsius
describe what happens during melting
The particles in a solid are held in fixed positions by strong bonds. Energy is needed to bre bonds. When the bonds are broken, the particles can move out of their fixed positions and slightly further apart from each other. The solid has melted. Melting takes place at the melting point without a change in temperature.
at which temperature does the ice melt
0 degrees celsius
describe what happens during boiling
The particles in a liquid have strong forces between them. Energy is needed to break the bonds and separate the particles further apart. Energy is also required for the particles to overcome the atmospheric pressure in order to escape into the air. When these happen, the liquid has boiled.
Boiling takes place at the boiling point without a change in temperature.
describe what happens during condensation
The reverse of boiling occurs. When a gas condenses into a liquid, forces pull the particles closer and energy is released.
