Topic 14 - Particle model Flashcards
Describe the arrangement of solids?
Strong force of attraction hold the particles close together in a fixed, regular arrangement. The particles dont have much energy in their kinetic energy stores to they only vibrate about their fixed positions
Describe the arrangement of liquids?
Forces of attraction between particles are weaker (than solids) The particles are close together but can move past each other and form irregular arrangements. They have more energy than solids so they move in random directions at low speeds
Describe the arrangement of gases?
There are almost no forces of attraction between the particles. Particles have the most energy in their kinetic energy stores and therefore, are free to move in random directions at high speeds
Recall the density equation
Density = mass / volume
Describe how to measure the density of an object that isnt a regular shape
- Measure mass (m1) of an object using a mass balance
- Fill a bottle with a liquid of known density
- Place the stopper into the bottle and dry the outside
- Measure mass of bottle (m2)
- Empty the bottle and place object into bottle. Repeat steps 2 and 3 then measure the mass of the bottle (m3)
- Calculate volume of displaced water by finding out mass of displaced water (m2 - (m3 - m1) and dividing it by density of water
- Calculate density of the object with the mass measured in step 1 and the volume measured in step 6
The energy in a substance’s thermal energy store is held by its particles in their ……
Kinetic energy stores
What happens when you boil a liquid?
The extra energy transferred into the particles kinetic energy stores makes them move faster. Until the attraction holding the particles together is broken and bubbles of gas form in the liquid
What happens when you melt a solid?
The extra energy makes the particles vibrate faster until eventually the forces between them are partly overcome and the particles start to move around
Is the mass of a substance affected when it changes state?
No, the mass stays the same as it is only the particles that are being rearranged
What happens to density when a substance changes shape?
Volume changes as particles become further/closer together. If volume changes, then density must change too.
Generally, out of the three states of matter, which ones are the most/least dense?
Most dense - solids
Least dense - gases
What is a substances ‘specific heat capacity’?
The change in energy in the substances thermal store needed to raise the temperature of 1kg of that substance by 1 degrees. e.g. water has a specific heat capacity of 4200 J/kg
What is the relationship between temperature and energy?
Heating a substance increases the energy in its thermal energy store
in kinetic theory, Temperature is a way of measuring ….
The average internal energy of a substance
What is the equation relating energy, mass, specific heat capacity, and temp
Change in thermal energy = mass * SHC * Temperature change
Describe how to find the SHC of water?
1) Use a mass balance to measure the mass of the insulating container
2) Fill the container with water and measure mass again. The difference in mass is the mass of the water in the container
3) connect joulemeter to container (place lid on container)
4) Measure temp of water, then turn on power
5) When temp has increased by 10 degrees, stop experiment and record energy on joulemeter and increase in temp
5) Calculate SHC by rearranging equation (repeat experiment 3 times and then find mean of SHC)
Describe an experiment that shows temperature doesnt go down until all of a substance changes state whilst they are e.g. condensing
- Fill a beaker with crushed ice
2, Place a thermometer in the beaker and record temp - Gradually heat the beaker with a bunsen burner
- Every 20 secs, record temp and current state of ice
- Continue process until water begins to boil
- Plot a temp against time graph
What should your temp/time graph look like?
Like stairs. It should look stationary when the water/ice is changing state
Why doesnt the temp go down when a substance is e.g. condensing?
Because bonds are forming between particles, which releases energy
What a substance is melting or boiling, energy is used for …………, rather than raising the temperature
breaking intermolecular bonds
What is the specific latent heat of the change of state of a substance?
The amount of energy needed to change 1kg of the substance from one state to another without changing the temperature
For cooling, SLH is ….
the energy released by a change in state
Define the ‘specific latent heat of fusion’
The SLH for changing between a solid and a liquid (melting or freezing)
Define the ‘specific latent heat of vaporisation?
the SLH for changing between a liquid and a gas (condensing, evaporating, boiling)
What is the equation that relates thermal energy, mass and SLH
Thermal energy = mass * specific latent heat
Explain the pressure of a gas in terms of the motion of its particles?
- As particles move at high speeds, they can collide with each other
- When they collide with something, they exert a force and therefore pressure on the object
What is the outward gas pressure in a sealed container? (sealed container)
the total force exerted, by all of the gas particles, on a unit area of the container walls
What effect does increasing temperature have on gas pressure of a fixed volume?
The higher the temp, the faster the particles move and the more often they collide with the container and the force exerted by the particles increase and therefore, increases gas pressure
What also increases with temperature during gas collisions? (APART FROM GAS PRESSURE)
The force exerted by each particle during a collision also increases
What effect does increase the volume of a gas have on gas pressure? (constant temp)
The particles are more spread and are less likely to collide with container so gas pressure decreases
Are pressure and volume directly proportional or inversely proportional?
They are inversely proportional
Define ‘absolute’ zero
Absolute zero is as cold as stuff can get - 0 kelvin
What happens if you cool a substance down? (in terms of energy)
You reduce the energy of the particles
What is the coldest temp (absolute zero) that anything can ever get and explain why it is the coldest temp?
-273 degrees celsius/ 0 kelvin and this is because at this point, the particles have as little energy in their kinetic stores as its possible to get
How do you convert from Celsius to Kelvin
Add 273
How do you convert from Kelvin to Celsius?
minus 273
What do the gas collisions in a container add up to produce? (in terms of forces)
They add up to produce a net overall force at right angles to the wall of the container
What can a change in pressure cause?
A change in volume
How can you change the pressure of a gas inside a container e.g. balloon?
- by heating/cooling
2. As balloon is heated, gas particles in it gain energy and move faster. This increases pressure of gas.
3. internal pressure is now larger than external pressure caused by surroundings. The balloon expands until the pressures are equal again
4. Cooling would have opposite effect and internal pressure would be less than external pressure
How could you change the external pressure of a gas?
- For a gas in an air-right syringe, pushing hard on the plunger increases the external pressure on the gas, so its larger than the internal pressure. This causes the gas in syringe to be compressed
- Atmospheric pressure decreases as altitude increases,so as a container of gas rises, the external pressure decreases. This causes the gas to expand as the altitude increases.
What does doing work on a gas increase?
It increases its temperature
Explain how doing work on a gas increases it temperature using a bicycle pump as an example?
In a bicycle pump:
- Gas exerts pressure on the plunger of the pump, and so exerts a force on it. Work is done against the force to push down the plunger
- This transfers energy to the kinetic energy stores of the gas particles, so increases the internal energy and therefore the temp
What is the equation to calculate pressure/volume at fixed mass at constant temperature?
P1 * V1 = P2 * V2
p = N/m2
