Physics 5 - Solids, Liquids and Gases Flashcards
What is the unit for density?
Kilogram/metre3 (kg/m3)
What is the unit for pressure?
Pascal (Pa)
What is the unit for specific heat capacity?
Joules/(Kilogram degree celsius) - (J/kg °C)
What is the equation linking density, mass and volume?
Density = Mass/Volume
ρ=m/V
Practical: Design an experiment to investigate density using direct measurements of mass and volume for a regular shaped object
Measure the mass using an electric mass balance
Measure the length of the sides using a ruler or digital calliper. If it is a circle or cylinder, use a digital calliper to work out the diameter, measuring at several points.
Work out the volume using an equation: lxwxh or πr^2×l
Use the density equation to calculate the density!
5.4 practical: Design an experiment to investigate density using direct measurements of mass and volume for an irregular shaped object
Measure the mass using an electric balance
Fill a measuring cylinder to a known volume (100ml), then place the object in and determine the hight change. This is the volume
Remember, 1ml = 1cm3
Use the density equation to work out density.
If the object is too large, use a eureka can and measure the displaced water to find the volume
What is the equation linking pressure, force and area?
Pressure = force/area
P=F/A
What direction does the pressure at a point in a gas or liquid act?
At rest it acts equally in all directions.
What is the equation linking pressure difference, height, density and gravitational field strength?
Pressure difference = density x height x gravitational field strength
p = h × ρ × g
5.8P Explain why heating a system will change the energy stored within the system
By increasing the kinetic energy of the particles, the system’s temperature increases (its energy has increased)
5.8P Describe and explain what two things can happen to an object when heated
Raise the temperature of the object - increased kinetic energy of the particles
Changing the state of the object - break the intermolecular bonds
5.9P Explain evaporation
It can happen below the boiling point and is caused by a particle escaping the surface of the liquid and becoming a gas - all particles have different energy levels.
Particles near the surface evaporate if:
- They are travelling in the right direction
- They are fast enough to overcome the intermolecular forces
5.9P Explain what happens to the temperature of a liquid when particles evaporate from it
The average energy (the temperature) decreases
5.11P practical: Design an experiment to obtain a temperature–time graph to show the constant temperature during a change of state
Get a beaker filled with ice, and place a thermometer inside.
Use a Bunsen burner to heat the ice, and measure the change in temperature every 30s (use a stopwatch to time it)
Continue this until the water boils for a minute
Plot the graph.
5.11P Sketch a temperature-time graph for ice being heated at a constant rate
SEE ONENOTE
Temperature increases until 0ºC, where it remains constant (the energy is being used to break the bonds and overcome the latent energy)
Temperature increases until 100ºC where it remains constant for a while again.
It then increases
If it is about steam cooling, it simply goes in the other direction
5.12P Define specific heat capacity, and what is its unit?
The energy required to increase the temperature of one kilogram of a substance by one degrees Celsius.
(J/kg ºC)
5.13P Write down the equation for change in thermal energy in terms of specific heat capacity
Change in thermal energy = mass x specific heat capacity x temperature change
ΔQ= m × c × ΔT
5.14P practical: Design an experiment to investigate the specific heat capacity of water
Find the mass of water (measure the container beforehand, using a mass balance)
Get the initial temperature of the water (thermometer)
Place an electric emersion heater into the water and connect an ammeter in series and voltmeter in parallel. Calculate the power by P = IV
Turn it on and measure the time that it is on (stopwatch)
Switch these two off after a rise of 10 degrees. Continue measuring the temperature and measure the maximum value.
Use this equation:
c=IVt/mΔT
Repeat and find the average
5.14P practical: Design an experiment to investigate the specific heat capacity of a metal cylinder
Do the same process as water but with a metal cylinder which has holes in it for the heater and thermometer.
5.15 Explain the motion of gas molecules
Random motion and speed - random collisions with the side of the container and other gas molecules
5.15 Explain pressure at a microscopic level
Molecules exert a force on the walls of the container (they change momentum when they collide and change direction)
This happens over area - P=F/A
5.16 Define absolute zero of temperature and give its value in ℃ and K
This is the lowest temperature possible, because particles have the smallest possible kinetic energy and no work can be extracted from the system. This happens at 0K=−273℃
5.17 Write down the relationship between the Kelvin scale and Celsius scales of temperature and give the significance of the Kelvin temperature scale
T(K)=T(℃)+273
or
T(℃)=T(K)−273
It is an absolute temperature scale as absolute zero is 0K. It goes up in the same increments as Celsius
5.19 Describe how the Kelvin temperature is related to the properties of gas molecules
It is proportional to the average KE of the molecules.
Celsius has a linear relationship but isn’t proportional.
- 20 explain, for a fixed amount of gas, the qualitative relationship between:
a. pressure and volume at constant temperature
Pressure is inversely proportional to volume.
The larger the container, the less dense the molecules are so they collide less often with the walls - lower pressure.
- 20 explain, for a fixed amount of gas, the qualitative relationship between:
b. pressure and Kelvin temperature at constant volume.
Pressure is proportional to Kelvin.
Higher temperature leads to higher KE, so there are more collisions with the walls and with more force - higher pressure
5.21 Write down the relationship between the pressure, Kelvin temperature and volume of a fixed mass of gas
P1V1/T1 = P2V2/T2
