Flashcards in Topic 3: Particle Model of Matter Deck (54):
A change of state requires what?
When a substance is melting or boiling, what is increased?
When a substance is melting or boiling, what is energy used for rather than raising the temperature?
Breaking inter-molecular bonds
What do the flat spots on a heating graph mean?
It is where energy is being transferred by heating but NOT being used to change the temperature
When a substance condenses or freezes, BONDS are formed between particles releasing what?
When a substance condenses or freezes, the internal energy decreases but what doesn't go down?
The temperature- until all the substances have turned to liquid (condensed) or a solid (frozen)
What do the flat lines of the graph show?
The energy needed to change the state of a substance is called the what?
Specific latent heat (of a substance)
It is the energy needed to change 1kg of the substance from one state to another without changing it's temperature
For cooling, specific latent heat is the energy released by what?
A change in state
Specific latent heat is different for different materials and for what?
Changing between different states
What is the name for the specific latent heat changing between a SOLID and LIQUID (melting or Freezing)?
Specific latent heat of FUSION
What is the name for the specific latent heat changing between a liquid and a gas (eVaporating, boiling or condensing)?
Specific latent heat of Vaporisation
Specific latent heat
Energy= mass x specific latent heat
Joules= kg x J/kg
or for SLH:
Specific latent heat= energy/mass
What can the particle model explain?
Density and the three states of matter
What is density?
The 'compactness' of a substance
It relates mass of a substance to how much space it takes up
density (kg/m2)= mass (kg)/ volume (m2)
When a material has it's particles packed tightly together it is?
The particles in a less dense material are?
Spread out- if you compressed the material, it's particles would move closer together, and it would become more dense (the mass wouldn't change but the volume would decrease)
Arrangement of a solid
STRONG forces of attraction hold the particles together in a fixed, regular arrangement. The particles don't have much energy so they can only vibrate about their positions. The density is generally highest in this state as the particles are closest together.
Arrangement of a liquid
WEAKER forces of attraction between the particles. The particles are close together, but can move past each other, and form irregular arrangements. They have more energy than the particles in a solid- they move in random directions at low speeds. Liquids are generally less dense than solids.
Arrangement of a gas
Almost NO forces of attraction between the particles. The particles have more energy than in liquids and solids- they're free to move, and travel in random directions at high speeds. Gases are generally less dense than liquids- they have low densities.
Finding the density of a solid object
1. Use a BALANCE to measure it's mass.
2. If a REGULAR solid, start by measuring it's length, width and height with a ruler. Then calculate it's volume using the relevant formula of the shape.
3. For an IRREGULAR solid, you can find it's volume by submerging it in a eureka can filled with water. The water displaced by the object will be transferred to the measuring cylinder.
4. Record the VOLUME of the water in the measuring cylinder. This is the volume of the object.
5. Apply the found object's mass and volume to the density formula to calculate DENSITY.
Finding the density of a liquid
1. Place a measuring cylinder on the BALANCE and measure 0.
2. Pour 10ml of the liquid into the measuring cylinder and record the liquid's mass.
3. Pour another 10ml into the measuring cylinder, repeating the process until the cylinder is full and recording the total volume and mass each time.
4. For each measurement, use the formula to find the density (1ml = 1cm3).
5. Finally, take an average of the calculated densities. This will give a value for the density of the liquid.
The particles in a gas are constantly moving with random directions and speeds. If you increase the temperature, you transfer energy into what?
The kinetic energy stores of it's particles
The temperature of a gas is related to what?
The average energy in the kinetic stores of the particles in the gas
The higher the temperature, the?
higher the average energy
As you increase the temperature of a gas, the average speed of it's particles does what?
Increases- this is because the energy in the particle's kinetic energy stores is 1/2mv2
Colliding gas particles create?
When particles collide with something they exert a force on it. In a sealed container, the outward gas pressure is what?
The total force exerted by all of the gas particles on a unit area of the container walls
Faster particles and more frequent collisions lead to what?
An increase in net force and an increase in gas pressure. Increasing the temperature will increase the speed and so the pressure as long as the volume is kept constant.
If the temperature is constant increasing the volume means what in terms of particle arrangement?
The particles are more spread out and hit the walls of the container less often. The gas pressure DECREASES.
Pressure and volume are?
Inversely proportional- when a volume increases, pressure decreases. When a volume decreases, pressure increases.
For a gas of fixed mass at a constant temperature, the relationship is: (formula)
pressure (Pa) x volume (m3)
What causes a net outwards force at right angles to the surface of it's container?
The pressure of a gas
There are net forces in the inside surface of a gas' container however there are also forces on the outside of the container due to what?
The pressure of the gas around it
If a container can easily change it's size (e.g. a balloon) what happens as a result of pressure changes?
It will cause for the container to either compress of expand due to the overall force
e.g. if a helium balloon is released it rises. Atmospheric pressure decreases with height so the pressure outside the balloon decreases. This causes the balloon to expand until the pressure inside drops to the same as the atmospheric pressure.
Work occurs when?
You transfer energy by applying a force
Doing work on a gas increases what?
It's internal energy which can increase it's temperature
You can do work on a gas mechanically. Give an example
Bike pump: the gas applies pressure to the plunger of the pump 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. If the pump is connected to a tyre, it should get warmer.
In cooling what occurs?
Particles loose energy and form bonds
Solid to liquid
Liquid to solid
Solid to gas
Gas to liquid
Liquid to gas
A change of state is a?
Physical change- meaning you do not end up with a new substance but just a different form of a substance
What happens if you reverse a change of state? e.g. freeze a substance that has been melted
The substance will return back to it's original form and get back it's original properties
Mass is conserved when the substance changes state. What does this mean?
The number of particles doesn't change, they're just arranged differently.
A change in state occurs if the substance is heated enough. Explain why using particle property
The particles will have enough energy in their kinetic energy stores to break up the bonds holding them together.
Heating the system transfers energy to it's particles (they gain energy in their kinetic energy stores and move faster) increasing the internal energy. What does this lead to?
A change in temperature or a change in state. If the temperature changes the size of the change depends on the mass of the substance, it's specific heat capacity (what it is made up of) and the energy input.
The energy stored in a system is stored by its?
Particles (molecules and atoms)
The internal energy of a system is?
The total energy that it's particles have in their kinetic and potential energy stores