Matter Flashcards
What is absolute zero?
0K - lowest possible temp. where particles don’t move
Why does everything theoretically stop at absolute zero?
All particles have the minimum possible kinetic energy as energy is proportional to temp.
What does a change in temperature mean?
Thermal energy has been transferred
What is thermal equilibrium?
When everything is the same temp
What is specific thermal capacity?
The amount of energy needed to raise the temperature of 1Kg of a substance by 1K
What is the unit for specific thermal capacity?
J Kg-1 K-1
How can you measure the specific thermal capacity in a lab?
Heat the substance with an electric heater so its temp. increases
Attach an ammeter and voltmeter to the electric heater so that work done can be calculated (W=VIt)
And then use q = mcΔT
What heater do you use when finding specific thermal capacity of a liquid?
Heating coil (or and electric heater)
Why is the experimental value of c higher than the actual value?
Energy from the heater is also transferred to the air and the container
Resistance in the circuit
How can you minimise the effects of heat dissipation when finding the specific thermal capacity experimentally?
Start below and finish above room temperature to cancel out gains and losses in energy
When is an ideal gas a good approximation?
Low pressure
High temp (compared to bp of substance)
What is Boyle’s Law?
At a constant temperature, the pressure and volume of a gas are inversely proportional
pV = constant
What does the graph of pressure - volume look like?
y=k/x graph
How does temperature affect a pressure - volume graph?
The higher the temperature the further the curve is from the origin
What is Charles’ Law?
At constant pressure, the volume of a gas is directly proportional to absolute temperature
V/T = constant
What does the graph of volume - temp look like?
Straight line graph that crosses the x-axis at 0K or -273°C
How do you test Boyle’s Law?
Use a pump and pressure gauge and change the pressure in a sealed tube with oil and air
Record pressure against volume (volume will change as pressure changes) and then times them together to get a constant
How do you test Charles’ Law?
Use a sealed capillary tube containing a drop of conc. sulfuric acid halfway up the tube, so that a column of air is trapped between the bottom of the tube and the acid drop
Place capillary tube in large beaker of water and record temperature of water against length of the column. Take repeats and averages.
Plot a graph of length against temperature (length is proportional to volume) and graph should be a straight line
What is the Pressure Law?
At constant volume, the pressure of a gas is directly proportional to temperature.
p/T = constant
What is the graph for pressure - temp?
Straight line that crosses x-axis at 0K or -273°C
How do you test the Pressure Law?
Submerge a flask that is connected to a Bourdon gauge in water. The volume of the tubing must be much less than the volume of the flask
Record the pressure of the air in the flask and the temperature of the water. Do repeats and take averages
Plot a graph of pressure against and temperature and should get a straight line
What is the ideal gas equation?
pV=nRT
How do you derive the ideal gas equation?
Combine the three gas laws to get the equation:
pV / T = constant
the constant depends on the amount of gas used and is equal to nR, where R is the gas constant
What is the value of the gas constant?
8.31 J mol-1 K-1
What is Avogadro’s constant?
Na 6.02 x 10 23 mol -1