State the equation to find the density of a material
Density(kg/m^3) = Mass(kg) / Volume(m^3)
ρ = m/V
What is the particle model used to explain
- The different states of matter
- Differences in density
Note:
AQA says that students should be able to recognise/draw simple diagrams to model the difference between solids,liquids and gases
What is the particle theory?
- In particle theory, you can think of the particles that make up matter as tiny balls
- You can explain the ways that matter behaves in terms of how these tiny balls move, and the forces between them
- The three states of matter are solid (e.g. ice), liquid (e.g. water) and gas (e.g. water vapour)
- The particles of a substance in each state are the same - only the arrangement and energy of the particles are different
How are solids arranged?
- Strong forces of attraction hold the particles close together in a fixed, regular arrangement
- The particles don’t have much energy so they can only vibrate about their fixed positions.
How are liquids arranged?
- There are 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
How are gases arranged?
- There are almost no forces of attraction between the particles
- The particles have more energy than in liquids and solids - they’re free to move, and are constantly moving with random directions and speeds
Practical 17
AAAA
What happens when substances change state?
Mass is conserved
Why are physical changes different to chemical changes?
Changes of state are physical changes which differ from chemical changes because the material recovers its original properties if the change is reversed
What is internal energy?
Energy is stored inside a system by the particles (atoms and molecules that make up the system)this is called internal energy
What is internal energy?
Internal energy is the total kinetic energy and potential energy of all the particles, (atoms and molecules) that make up a system
What does heating do to an object?
- Heating the system transfers energy to its particles (they gain energy in their kinetic stores and move faster), increasing the internal energy
- This either raises the temperature of a system produces a change of state
What happens if the temperature of a system increases?
The increase in temperature depends on the mass of a substance, heated the type of material and the energy input into the system
How do you find change in thermal energy?
Change in thermal energy(J) = Mass(kg) x Specific heat capacity(C) x Temperature change(C)
△E = mc△θ
What is latent heat?
The energy needed for a substance to change
What happens when a change of state occurs?
- The energy needed for a substance to change that is called latent heat
- When a change of state occurs,the energy supplied changes the energy stored (internal energy) but not the temperature
What is the specific latent heat of a substance?
The specific latent heat (SLH) of a substance is the amount of energy needed to change 1 kg of it from one state to another without changing its temperature
How do you find energy for a change of state?
Energy for a change of state(J) = Mass(kg) x Specific latent heat(J/kg)
Note:
Check CHP Page 194 and memorise the heating and cooling graphs that include the change of state
What is specific heat capacity?
The specific heat capacity of a material is the energy required to raise one kilogram (kg) of the material by one degree Celsius (°C).
How are molecules in a gas moving
They are moving at a constant random motion
What is the temperature of a gas related to?
The kinetic energy of the molecules
What happens if you change the temperature of a gas held at a constant volume?
It changes the pressure exerted by the gas
