# AQA Topic 3 - Particle Model of Matter 9-1

• Created by: Grace
• Created on: 10-05-18 16:13
Define density
A measure of the compactness of a su stance, it relates the mass of a substance to how much space it takes up
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Give the equation for density
Density = mass(kg) ÷ volume(m3)
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What are the symbols for density, mass and volume?
ρ, m and v
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How do you convert from g/cm3 to kg/m3?
1 g/cm3 = 1000 kg/m3
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What does an object's density depend on?
What the object's made of and its particle arrangement
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What's the difference between a dense and less dense material?
A dense object is an object that has its particles packed tightly together whereas a less dense material are more spread out
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What happens when you compress a less dense object? Why?
Its particles would move closer together, making it more dense. This is because you're decreasing its volume but not its mass
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What is the difference between the states of matter?
The particles of a substance in each state are the same - only the arrangement and energy of the particles are different
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Describe the state of solids
Strong forces of attraction hold the particles close together in a fixed, regular arrangement. The particles don't have much energy = they can only vibrate about their fixed positions. The density is norm highest in this state bc of the particles
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Describe the state of liquids
Weaker forces of attraction between the particles so they are close but can move past each other and form irregular arrangements. They have more energy than the particles in a solid + move in random directions at low speeds. Gen less dense than solid
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Describe the state of gases
Almost no forces of attraction between the particles, these particles have the most energy = they are free to move and travel in random directions at high speeds. They have low densities
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Describe how to find the density of a solid object (1)
1. Measure its mass 2. If it is a regular object, find it's volume by measurements but if its irregular find its volume by submerging it in a eureka can filled with water. The water displaced by the object will be transferred to the measuring
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Describe how to find the density of a solid object (2)
cylinder 3. Record the volume of water in the measuring cylinder - this is the volume of the object 5. Use the formula to find its density
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Describe how to find the density of a liquid (1)
1. Pour 10ml of the liquid into a measuring cylinder on a balance and record its mass 2. Pour another 10ml into the measuring cylinder and repeat the process until the cylinder is full and record the total vol + mass each time 3. Use the density
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Describe how to find the density of a liquid (2)
formula 4. Take an average of the calculated densities, this will give you the density value
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What is 1ml equal to?
1cm3
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Define internal energy
Internal energy is the energy stored by the particles that make up a system
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What do particles in a system vibrating/moving mean?
They have energy in the kinetic energy store and they also have energy in their potential energy store due to their positions
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Define internal energy of a system
The internal energy of a system is the total energy that its particles have in their kinetic and potential energy stores
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What happens if you heat a system?
Heating the system transfers energy to its particle stores - they gain energy in their kinetic stores and move faster - which increases the internal energy
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What does heating a system lead to? Why?
A change in temperature or a change of state. If the temperature changes, the size of the change depends on the mass of the substance - what its made of (its specific heat capacity) and the energy input
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How does a change of state occur?
If the substance is heated enough the particles will have enough energy in their kinetic energy stores to break the bonds holding them together
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Complete the sentence: A change of ___ conserves ___
1. State 2. Mass
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Why does a change of state conserve mass?
The number of particles don't change in a state change, they are only arranged differently
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What happens when a substance is melting or boiling?
When a substance is melting or boiling you're still putting in energy and so increasing the internal energy but the energy's being used for breaking intermolecular bonds rather than raising the temperature.
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On a temperature/time graph, what do 'flat spots' represent?
They show where energy is being transferred by heating but not being used to change the temperature
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What happens when a substance is condensing or freezing?
Bonds are forming between the particles which release energy. This means the internal energy decreases but the temperature does no until all the substance has changed state
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What is the energy needed to change state of a substance called?
Latent heat
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Define specific latent heat
The energy needed to change the state of 1kg of a substance without changing its temperature
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What is specific latent heat in cooling?
The energy released by a change in state
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True or False: Specific latent heat is the same for all materials
False, its different for different materials and for changing between different states
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What is the specific latent heat called for changing between a solid and liquid?
Specific latent heat of fusion
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What is the specific latent heat called for changing between a liquid and a gas?
Specific latent heat of vaporisation
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What is the temperature of a gas related to?
The average energy in the kinetic energy stores of the particles in a gas. The higher the temperature, the higher the average energy
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Explain what happens when you increase the temperature of a gas
The average speed of its particles increase because the energy in the particles' kinetic energy stores is 1/2mv2
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In relation to gas particles, what happens in a container?
As gas particles move around at high speeds, they bang into each other and other things. When they collie with something they exert a force - pressure.
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In a sealer container, what is the outward gas pressure equal to?
The outward gas pressure is the total force exerted by all particles in the gas on a unit area of the container walls
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What do faster particles lead to?
Faster particles = more frequent collisions = increase in net force = increase in gas pressure. Therefore increasing the temperature will increase the speed which will increase the pressure, if the volume is constant
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Complete the sentences: If temperature is ____, increasing the volume of a gas mean the particles get ____ spread out and hit the walls of the container ____ often therefore the gas pressure _____
1. Constant 2. More 3. Less 4. Decreases
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True or False: Pressure and volume are inversely proportional
True because when the volume goes up the pressure goes down for a gas at fixed mass at a constant temp.
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What can a change in pressure cause?
A change in volume
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What does the pressure of a gas cause inside its container?
It causes a net outwards force at right angles to the surface of its container. There is also a force on the outside of the container due to the pressure of the gas around it
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What happens if a container can change its shape easily?
If a container can easily change it size then any change in the pressures will cause the container to compress or expand due to the overall force
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Explain why a helium ballon rises if its released
Atmospheric pressure decrease with height so the pressure outside the ballon decreases. This causes the ballon to expand until the pressure inside drops to the same as the atmospheric pressure
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How does doing work on a gas increase its temperature?
Doing work on a gas increases its internal energy which can increase is temperature
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What happens when work is done on a gas mechanically i.e with a bike pump?
The gas applies pressure to the plunger of the pump and so exerts a force on it. Work has to be done against this force to push down the plunger. This transfers energy to the kinetic energy stores of the gas particles, increasing the temperature
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## Other cards in this set

### Card 2

#### Front

Give the equation for density

#### Back

Density = mass(kg) ÷ volume(m3)

### Card 3

#### Front

What are the symbols for density, mass and volume?

### Card 4

#### Front

How do you convert from g/cm3 to kg/m3?

### Card 5

#### Front

What does an object's density depend on?