Kinetic theory (Unit 2) Flashcards
Kinetic molecular model of a:
1-Solid
2-Liquid
3-Gas
1-Fixed shape and volume, with high density and won’t flow.
2-Takes the shape of bottom of the container it’s in, has a fixed volume, medium density and it flows.
3-Takes up the shape and volume of the container it’s in, has a low density and it flows.
Describe/explain Brownian Motion and give an example
- Brownian motion is the random jerky motion of particles viewed through a microscope.
- It’s caused by rapid collisions between moving invisible particles(molecules) and larger other particles. They collide then bounce off each other.
- E.g. dust particles in the air or pollen grains in water.
Describe the movement of a particle in Brownian motion
Moves in a total long way (jerky moments) but doesn’t move far from the point in the center.
The space and attraction between molecules in:
1-Solids
2-Liquids
3-Gases
1-High forces and small spaces. Fixed shape.
2-Medium forces and small spaces. Random motion.
3-Very low forces and large spaces. Random motion of molecules.
Describe a short experiment to demonstrate evaporation
Put some ethanol onto the back of your hand. It feels a little cold and the ethanol evaporates off your hand. If you give it a blow it increases the rate at which the reaction occurs.
Evaporation increases when? (3)
- Its warmer
- Wind is supplied
- A greater surface area
Boyle’s law
- Pressure and volume are inversely proportional.
- pV = constant
- P1V1 = P2V2
- Temperature remains constant.
What happens to the molecules when they expand due to heat and what is this process called?
- Thermal expansion
- The molecules move/(vibrate if it’s a solid) faster so the gaps between the molecules increase.
When thermal expansion occurs.
Order the 3 states into the order of how much they expand. (Lowest to highest)
- Solid
- Liquid
- Gas
Uses of thermal expansion? (2)
- Thermometers
- Thermostats
What is a thermostat? Describe the experiment.
Take a bimetallic strip and hold it above a flame from a bunsen burner. The strip will bend away from the flame. This is because the molecules at the bottom of the bimetallic strip (that’s closest to the flame) expands.
Disadvantages of thermal expansion? (3)
- Bridges (don’t want them to expand)
- Power lines (can break)
- Freezing pipes (can burst)
- What are fixed points?
- Fixed points of water?
- The freezing and boiling point of a substance
- 0 degree C and 100 degree C
Define sensitivity
The expansion (or change) per degree celcius
Define linearity
The same expansion (or change) per degree celcius
What does the range of a thermometer depend on?
The boiling point and freezing points of the liquid or other properties as well.
What apparatus is used to measure temperature difference between 2 different metals?
Thermocouple
Describe the wires of a thermocouple and give examples of each
- There are 3 wires.
- Wires 1 and 2 are made of the same material e.g. copper
- Wire 3 is different to wires 1 and 2 e.g. constantan
You can’t have 2 wires made of very conductive metals or both that are made of very conductive metals.
You would have one of each.
What must the junction have on a thermocouple?
2 different wires meeting at the junction
How do the wires cause a voltage in a thermocouple?
Examples of meters that are used to measure the voltage produced. (4)
The two different wires joined together, at the same temperature will cause a voltage. This is read on a meter such as:
- Galvanometer
- Millivoltmeter
- Milliammeter
- Digital voltmeter or ammeter
In a thermocouple what is commonly done with the cold junction?
It’s put into ice. This is so we can compare the temperature to a known valur (0 degree C)
Advantages of a thermocouple? (6)
- Rapid response to change in temperature
- Small thermal capacity - doesn’t affect the measurement
- Can be used as a data logger for continuous measurement
- Can measure a large range
- Has a small area
- Can be used for remote readings if connected via the internet to a PC and the internet
What is the internal energy?
The internal energy is the sum of all the KE and PE energies of its atoms/ molecules
How do you increase the internal energy? (2)
- Supply more thermal energy
- Doing work on the system e.g. compressing it
Define heat capacity
Heat capacity is the amount of energy required to raise the temperature of a body by 1K or 1 degree C
Define specific heat capacity
Specific heat capacity is the amount of energy required to raise 1Kg (unit mass) of a substance by 1K or 1 degree C
Specific heat capacity = ?
Include units and symbols
specific heat capacity = energy supplied / (mass * delta feta(or temperature))
C = Q / (m*delta T)
Specific heat capacity = C (J/kg/degree C)
Energy supplied = Q (J)
Change in temperature = delta T(or feta) (degree C)
1-What is latent heat of fusion?
2-What is latent heat of vaporisation?
1-Solid to a liquid vice-versa
2-Liquid to gas vice-versa
Define specific latent heat
Specific latent heat is the energy needed per Kg of a substance to change the state
Specific latent heat of fusion = ?
Include units and symbols
Specific latent heat of fusion = energy supplied / mass of substance melted
L = Q / M
L = specific latent heat (J/Kg) Q = energy supplied (J) M = mass (kg)
Remember to use the E = Pt or E = VIt if Q is not directly given to you.
If you use g for mass then change the unit for L to J/g
Specific latent heat of vaporisation = ?
Include units and symbols
Specific latent heat of vaporisation = energy supplied / mass of substance vaporised
L = Q / M
L = specific latent heat of vaporisation (J/kg) Q = energy supplied (J) M = mass (kg)
Remember to use the E = Pt or E = VIt if Q is not directly given to you.
If you use g for mass then change the unit for L to J/g
Rules for latent heat? (2)
- Energy is supplied to melt or boil a substance
- Energy is given out on freezing or condensation
4 methods of heat transfer and what they can happen in
- Conduction = mainly solids
- Convection = fluids
- Radiation = doesn’t require a medium so it can happen in a vacuum
- Evaporation
Thermal radiation is the same as what?
Infrared radiation which is an EM wave
1-What objects are better are absorbing and emitting radiation?
2-What objects are worse at absorbing and emitting radiation? Why?
1-Dull and dark objects
2-Shiny and light objects. Shiny objects reflect light.
Ways to insulate a house? (5)
- Double glazing
- Cavity wall insulation
- Loft insulation
- Insulate hot water tank - so you don’t waste heat
- Turn down the radiators
