Particle Model of Matter

Question 1

How does particle theory say we must consider particles?

Answer 1

Each particle as a small, solid, inelastic sphere

Question 2

What is particle theory also known as?

Answer 2

Kinetic theory

Question 3

Describe the particles in a solid

Answer 3

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.

Question 4

What happens when you heat a solid?

Answer 4

The particles vibrate more and more until they have enough energy to weaken their bonds (at melting point), turning into a liquid

Question 5

Describe the particles in a liquid

Answer 5

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

Question 6

What happens when you heat a liquid?

Answer 6

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

Question 7

Describe the particles in a gas

Answer 7

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

Question 8

What happens when you heat a gas

Answer 8

Particles get more energy, so travel faster so expands if in a expandable container. If in a fixed container, the pressure increases

Question 9

What happens when you cool a gas?

Answer 9

The particles will lose thermal and therefore kinetic energy, and won’t have enough to overcome the forces between them - they condense

Question 10

What happens when you cool a liquid

Answer 10

Particles lose energy and wont have enough to overcome the attraction between them, so more bonds form, freezing it into a solid

Question 11

In a closed system, what happens in terms of mass and density when changing state of matter?

Answer 11

• 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)

Question 12

What is density?

Answer 12

How much mass a substance has per unit of its volume

Question 13

What is the equation for density?

Answer 13

Density = mass/volume
generally in kg/m^3

Question 14

How do you find the mass of a solid object?

Answer 14

Put it on a balance and measure

Question 15

How do you find the volume of a regular shape?

Answer 15

Measure and multiply its width, length and height

Question 16

How do you find the volume of an irregular shape?

Answer 16

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

Question 17

How do you find the density of a liquid?

Answer 17

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

Question 18

The larger the volume of liquid, the more ____ the density calculated will be - why?

Answer 18

The more accurate the density will be. This is because using a larger volume minimises the effects of uncertainty

Question 19

When trying to calculate density, what would be good to do?

Answer 19

Take multiple measurements to cancel out anomalies and calculate a mean

Question 20

What are the limitations of particle theory

Answer 20

• 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

Question 21

What does heating up a substance do to internal energy?

Answer 21

increases internal energy, as kinetic energy contributes

Question 22

What is temperature?

Answer 22

A measure of the average internal energy of all the particles in a substance

Question 23

Why are there straight lines on a graph showing the heating of a substance?

Answer 23

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

Question 24

Why are there straight lines on a graph showing the cooling of a substance?

Answer 24

There is a formation of new bonds as the substance changes state, which releases energy and counteracts the cooling, cause temp to be constant

Question 25

What is latent heat?

Answer 25

The amount of energy required to change the state of a substance while temp remains the same

Question 26

What is latent heat dependent on?

Answer 26

- the type of substance the amount of substance

Question 27

What is specific latent heat?

Answer 27

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)

Question 28

What is the specific latent heat of vaporisation?

Answer 28

The energy change when a substance changes between a liquid and a gas (evaporation or condensation)

Question 29

What is the specific latent heat of fusion?

Answer 29

The energy change when a substance changes between a solid and a liquid

Question 30

What is the equation for specific latent heat

Answer 30

energy required or released = mass x specific latent heat (J/kg)

Question 31

How do particles in a gas create pressure?

Answer 31

They are free to move around, so when they collide with a wall, they exert a force, which creates pressure

Question 32

What is the equation for pressure?

Answer 32

Pressure = force / area pressure is force exerted per unit of area

Question 33

What contributes to the total pressure of a gas?

Answer 33

The frequency of collisions and how much energy each collision involves

Question 34

What are the factors affecting pressure?

Answer 34

Temperature, concentration and volume

Question 35

How does temperature affect gas pressure (fixed container)?

Answer 35

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

Question 36

How does concentration affect gas pressure (fixed container)?

Answer 36

Increases the number of particles but keeping volume the same increases concentration. This means that there will be more collisions, meaning a higher pressure

Question 37

How does volume affect gas pressure (fixed container)?

Answer 37

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

Question 38

If a gas is in an expandable container, how do concentration and temperature affect it?

Answer 38

They change the volume rather than pressure, as it will just expand with number and force

Question 39

What is the relationship between pressure and volume?

Answer 39

They are inversely related - as one goes up, the other goes down

Question 40

When is pressure x volume = constant?

Answer 40

When there is a given amount of gas at a constant temperature

Question 41

What is the equation for pressure and volume?

Answer 41

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

Question 42

What is internal energy and what is it made up of?

Answer 42

The total energy stored by the particles making up a substance or system - said to be made up of the potential and kinetic energy stores

Question 43

What is specific heat capacity?

Answer 43

The amount of energy needed to raise the temp of 1kg of a substance by 1 degree Celsius