Particle Model of Matter Flashcards
How does particle theory say we must consider particles?
Each particle as a small, solid, inelastic sphere
What is particle theory also known as?
Kinetic theory
Describe the particles in a solid
Strong forces of attraction between the particles which holds them all together in a fixed position. This forms a regular lattice structure and means it keeps a definite shape and volume. They don’t flow, rather vibrate.
What happens when you heat a solid?
The particles vibrate more and more until they have enough energy to weaken their bonds (at melting point), turning into a liquid
Describe the particles in a liquid
Have weak forces of attraction so are free to move around each other, and are arranged randomly. However, the weak FoA mean that it is compact, so they have a definite volume though their shape can change and fit a container
What happens when you heat a liquid?
Particles gain more energy, so they move around faster, weakening FoA holding them together. At boiling point, the particles have enough energy to break bonds altogether, becoming a gas
Describe the particles in a gas
Very weak FoA, so are free to move around, and don’t have a definite shape or volume. They are constantly moving with random motion
What happens when you heat a gas
Particles get more energy, so travel faster so expands if in a expandable container. If in a fixed container, the pressure increases
What happens when you cool a gas?
The particles will lose thermal and therefore kinetic energy, and won’t have enough to overcome the forces between them - they condense
What happens when you cool a liquid
Particles lose energy and wont have enough to overcome the attraction between them, so more bonds form, freezing it into a solid
In a closed system, what happens in terms of mass and density when changing state of matter?
- won’t change the mass (as there are still the same no. of particles)
- the density of the substance will change (solids have highest, gases have lowest)
What is density?
How much mass a substance has per unit of its volume
What is the equation for density?
Density = mass/volume
generally in kg/m^3
How do you find the mass of a solid object?
Put it on a balance and measure
How do you find the volume of a regular shape?
Measure and multiply its width, length and height
How do you find the volume of an irregular shape?
Use a eureka can:
Fill it to the brim below its outlet with water, place the object in the can, and collect + measure the volume of water collected. The volume of water will be equal to the volume of the solid
How do you find the density of a liquid?
Place a measuring cylinder on a balance, zero the balance and pour in a set amount of liquid (e.g. 10ml which = 10cm^3) and record the mass
Divide the mass by the volume used
The larger the volume of liquid, the more ____ the density calculated will be - why?
The more accurate the density will be. This is because using a larger volume minimises the effects of uncertainty
When trying to calculate density, what would be good to do?
Take multiple measurements to cancel out anomalies and calculate a mean
What are the limitations of particle theory
- misrepresents the structure of particles
- doesn’t show the strength or nature of forces between particles
- all particles are shown as the same size and type, but they aren’t really
What does heating up a substance do to internal energy?
increases internal energy, as kinetic energy contributes
What is temperature?
A measure of the average internal energy of all the particles in a substance
Why are there straight lines on a graph showing the heating of a substance?
The energy the we provide is being to weaken or break forces holding particles together during a change of state, rather than increasing the particles internal energy
Why are there straight lines on a graph showing the cooling of a substance?
There is a formation of new bonds as the substance changes state, which releases energy and counteracts the cooling, cause temp to be constant
What is latent heat?
The amount of energy required to change the state of a substance while temp remains the same
What is latent heat dependent on?
- the type of substance
the amount of substance
What is specific latent heat?
The energy required to change 1kg of a substance from one state to another without changing its temperature.
(for cooling, the amount of energy released by a change of state)
What is the specific latent heat of vaporisation?
The energy change when a substance changes between a liquid and a gas (evaporation or condensation)
What is the specific latent heat of fusion?
The energy change when a substance changes between a solid and a liquid
What is the equation for specific latent heat
energy required or released = mass x specific latent heat
(J/kg)
How do particles in a gas create pressure?
They are free to move around, so when they collide with a wall, they exert a force, which creates pressure
What is the equation for pressure?
Pressure = force / area
pressure is force exerted per unit of area
What contributes to the total pressure of a gas?
The frequency of collisions and how much energy each collision involves
What are the factors affecting pressure?
Temperature, concentration and volume
How does temperature affect gas pressure (fixed container)?
Heating a substances causes more energy in its kinetic energy store, which means the particles move around more, causing more frequent collisions, and each collision would exert more force. Therefore, pressure increases with temperature
How does concentration affect gas pressure (fixed container)?
Increases the number of particles but keeping volume the same increases concentration. This means that there will be more collisions, meaning a higher pressure
How does volume affect gas pressure (fixed container)?
Keeping the no. of particles the same, but decreasing the volume, there would be more particles per unit volume, which is the same as a higher concentration. Because there is less distance to travel between each collision, there will be more collisions. So, as volume decreases, pressure increases
If a gas is in an expandable container, how do concentration and temperature affect it?
They change the volume rather than pressure, as it will just expand with number and force
What is the relationship between pressure and volume?
They are inversely related - as one goes up, the other goes down
When is pressure x volume = constant?
When there is a given amount of gas at a constant temperature
What is the equation for pressure and volume?
pressure x volume = constant
SO, if one goes down, the other would go up, keeping the number the same
This works as the two are inversely related
