Particle Model of Matter Flashcards
What is the definition of density? State the relevant equation with units
- the mass per unit volume of a material
- p=m/v
- density (kg/m^3), mass (kg), volume (m^3)
State the different states of matter in order (least to most) of density of atoms
gas, liquid, solid
Describe the particle arrangement of a solid
tightly packed in a regular arrangement, particles can only vibrate on the spot
Describe the particle arrangement of a liquid
close together, but with an irregular arrangement, they can flow over each other
Describe the particle arrangement of a gas
separated, with no regular arrangement, particles can move freely
What is always conserved when a substance undergoes a change of state?
mass
How does a change of state differ from a chemical change?
in a change of state, the material can return to having its previous properties if the change is reversed
What is sublimation?
when a solid changes to a gas without passing through a liquid state
What is evaporation?
when a liquid changes into a gas state
What is the opposite of evaporatin?
condensation, which is when a gas changes into a liquid state
When water boils in an open pan, why does the mass of the pan of water appear to decrease?
some of the water will evaporate and turn into water vapour, this will leave the pan meaning the mass of the pan will decrease, however the mass of the whole system remains constant
Explain the processes involved when a bathroom mirror mists up
- hot water evaporates in water vapour
- this water vapour lands on the cooler mirror
- the vapour condenses and returns to liquid state on the mirror’s surface
What is the internal energy of a substance?
- the energy stored by the particles
- the sum of the total kinetic and potential energies that make up the system
How does the heating affect the energy of a substance?
- heating transfers energy to the substance
- it increases the energy of the particles that make up the substance
What 2 things can heating a substance do?
raise its temperature and change the state of the substance
What 3 factors determine the temperature change of a system?
- mass of substance being heated
- type of material (Specific heat capacity)
- energy inputted into the system
State the equation used to calculate the temperature change when a substance is heated, give appropriate units
energy change = mass x specific heat capacity c temperature change
(J, kg, J/kg/degrees celsius, degrees celsius)
Define specific heat capacity
the amount of energy needed to increase the temperature of 1kg of a substance by 1 degrees celcius
Describe how the internal energy and temperature of a substance changes when a change of state occurs
- internal energy of the substance will be increased or decreased
- temperature of the substance will remain constant
Define specific latent heat
the amount of energy needed to change the state of 1kg of a substance with no change in temperature
State the equation for the energy required to change state. Give appropriate units
- energy to change state = mass x specific latent heat
- energy (J), mass (kg), specific latent heat (J/kg)
What is the specific latent heat of fusion?
the energy required the change 1kg of a substance from solid state to liquid state without a change in temperature
What is the specific latent heat of vaporisation?
the energy required to change 1kg of a substance from liquid state to gas state (vapour) without a change in temperature
Describe the motion of molecules in a gas
they are in constant random motion
What factor affects the average kinetic energy of gas molecules?
- the temperature of the substance
- the higher the temperature, the higher the average kinetic energy of the molecules
What effect does increasing temperature have on the pressure of a gas when held at constant volume?
pressure of the gas will increase as the temperature increases
Why does pressure increase as temperature increases (at a constant volume)?
- kinetic energy of molecules increases
- collisions between molecules becomes more frequent
- greater rate of change of momentum
- greater force and therefore pressure
If gas A is at a low pressure, and gas B is at a high pressure, what can be said about the rate of collisions in each gas?
- there are more collisions per second in gas B than in gas A
- the rate of collisions in higher in B
Describe the force that the pressure of a gas exerts on the walls of its container
- the net force acts at right-angles to the container’s surface
- the force increases as pressure increases
Explain how increasing the volume of a gas results in a decrease of pressure
- molecules become more spread out and so time between collisions increases
- this reduces the rate of collisions
- rate of change of momentum decreases, and so force exerted on container decreases, resulting in a lower pressure
What can be said about the product of pressure and volume for a fixed mass of gas at a constant temperature?
it is constant
p V = constant
What is the unit used for pressure?
Pascal (Pa)
What increases when you do work on a gas?
- the internal energy of the gas
- this can also lead to an increase of temperature
Why does the temperature of air inside a bike pump increase when it is pumped?
- work is done on a gas when it is compressed
- doing work on a gas increases its internal energy, so also increases the average kinetic energy of the molecules
- temperature increases with an increase of average kinetic energy
