1. The Particulate Nature of Matter

Question 1

Describe the attractive forces in solids

Answer 1

Strong forces of attraction between particles, particles are packed very closely together in a fixed and regular pattern

Question 2

Describe the attractive forces in liquids

Answer 2

Weaker attractive forces in liquids than in solids, particles are close together in an irregular, unfixed pattern

Question 3

Describe the attractive forces in gases

Answer 3

No intermolecular forces, particles are in random movement and so there is no defined pattern

Question 4

Describe the movement in solids

Answer 4

Atoms vibrate in position but can’t change position or move

Question 5

Describe the movement in liquids

Answer 5

Particles can move and slide past each other which is why liquids adopt the shape of the container they’re in and also why they are able to flow

Question 6

Describe the movement in gases

Answer 6

Particles are far apart and move quickly (around 500 m/s) in all directions, they collide with each other and with the sides of the container (this is how pressure is created inside a can of gas)

Question 7

Describe the fixed volume and density in solids

Answer 7

solids have a fixed volume, shape and high density

Question 8

Describe the fixed volume and density in liquids

Answer 8

Liquids have a fixed volume but not a fixed shape and have a moderate to high density

Question 9

Describe the fixed volume and density in gases

Answer 9

No fixed volume, since there is a lot of space between the particles, gases can be compressed into a much smaller volume. Gases have low density

Question 10

What change occurs during melting?

Answer 10

Melting is when a solid changes into a liquid

Question 11

What does melting require?

Answer 11

Requires heat energy which transforms into kinetic energy, allowing the particles to move

Question 12

When does melting occur?

Answer 12

Occurs at a specific temperature known as the melting point (m.p.) which is unique to each pure solid

Question 13

What change occurs during boiling?

Answer 13

Boiling is when a liquid changes into a gas

Question 14

What does boiling require?

Answer 14

Requires heat which causes bubbles of gas to form below the surface of a liquid, allowing for liquid particles to escape from the surface and within the liquid

Question 15

When does boiling occur?

Answer 15

Occurs at a specific temperature known as the boiling point (b.p.) which is unique to each pure liquid

Question 16

What change occurs during freezing?

Answer 16

Freezing is when a liquid changes into a solid

Question 17

When does freezing occur?

Answer 17

This is the reverse of melting and occurs at exactly the same temperature as melting, hence the melting point and freezing point of a pure substance are the same. Water for example freezes and melts at 0ºC

Question 18

What does freezing require?

Answer 18

Requires a significant decrease in temperature (or loss of thermal energy) and occurs at a specific temperature which is unique for each pure substance

Question 19

What change occurs during evaporation?

Answer 19

When a liquid changes into a gas.

Question 20

What is the difference between boiling and evaporation?

Answer 20

Evaporation occurs only at the surface of liquids where high energy particles can escape from the liquid’s surface at low temperatures, below the b.p. of the liquid

Question 21

What increases the rate of evaporation?

Answer 21

The larger the surface area and the warmer the liquid/surface, the more quickly a liquid can evaporate

Question 22

What is required for evaporation? (if anything)

Answer 22

No energy is required for evaporation to occur and it takes place over a range of temperatures

Question 23

What change occurs during condensation?

Answer 23

When a gas changes into a liquid, usually on cooling

Question 24

How does condensation occur (in terms of particles)?

Answer 24

When a gas is cooled its particles lose energy and when they bump into each other they lack the energy to bounce away again, instead they group together to form a liquid

Question 25

What is required for condensation? (if anything)

Answer 25

No energy is required for condensation to occur and it takes place over a range of temperatures

Question 26

What change occurs during sublimation?

Answer 26

When a solid changes directly into a gas

Question 27

What example of solids can undergo sublimation?

Answer 27

This happens to only a few solids such as iodine or solid carbon dioxide

Question 28

What is the reverse reaction of sublimation?

Answer 28

The reverse reaction also happens and is also called sublimation (sometimes called deposition or desublimation)

Question 29

When does sublimation occurr?

Answer 29

Sublimation occurs at a specific temperature which is unique for a pure substance

Question 30

In what type of motion are gaseous particles in?

Answer 30

Gaseous particles are in constant and random motion

Question 31

What happens to gaseous particles when there is an increase in temperature?

Answer 31

An increase in temperature increases the kinetic energy of each particle, as the thermal energy is transformed to kinetic energy, so they move faster

Question 32

What causes pressure in a container?

Answer 32

The pressure that a gas creates inside a closed container is produced by the gaseous particles hitting the inside walls of the container.

Question 33

What is the effect of increasing temperature on pressure?

Answer 33

• As the temperature increases, the particles in the gas move faster, impacting the container’s walls more frequently
• Therefore an increase in temperature causes an increase in pressure

Question 34

Brownian Motion definition

Answer 34

Brownian motion is defined as the random movement of particles in a liquid or a gas produced by large numbers of collisions with smaller, often invisible particles

Question 35

What does the observation of brownian motion prove?

Answer 35

the correctness of the kinetic particle theory

Question 36

Diffusion definition

Answer 36

This is the process by which different gases or different liquids mix and is due to the random motion of their particles

Question 37

From where to where do diffusing particles move?

Answer 37

Diffusing particles move from an area of high concentration to an area of low concentration, till the concentration of particles is even

Question 38

Does diffusion require energy?

Answer 38

NO

Diffusion happens on its own and no energy input is required although it occurs faster at higher temperatures

Question 39

What is the basis of the kinetic theory of matter?

Answer 39

When substances are heated, the particles absorb thermal energy which is converted into kinetic energy

Question 40

What happens when you heat a solid?

Answer 40

Heating a solid causes its particles to vibrate more and as the temperature increases, they vibrate so much that the solid expands until the structure breaks and the solid melts

Question 41

What happens when you heat a liquid?

Answer 41

On further heating, the now liquid substance expands more and some particles at the surface gain sufficient energy to overcome the intermolecular forces and evaporate

Question 42

What happens when the b.p. temperature is reached in a liquid?

Answer 42

When the b.p. temperature is reached, all the particles gain enough energy to escape and the liquids boils

Question 43

What type of graph can be used to show how changes in temperature affect changes in state?

Answer 43

A heating curve - solid to gas

A cooling curve - gas tp solid

Question 44

What is an example of Brownian Motion?

Answer 44

An example of Brownian motion is the observed jerky and erratic motion of smoke particles as they are hit by the unseen molecules in the air which can be seen under a microscope

Question 45

What is the basic condition needed to show the Brownian process is occurring?

Answer 45

In all cases, larger and visible particles are caused to move by the random bombardment of smaller, invisible particles

Question 46

In what state does diffusion happen the fastest?

Answer 46

Diffusion occurs much faster in gases than in liquids as gaseous particles move much quicker than liquid particles

Question 47

Do gases diffuse at different rates at the same temperature?

Answer 47

YES

- At the same temperature, different gases do not diffuse at the same rate.

Question 48

What causes the difference in the rate of diffusion in gases?

Answer 48

This is due to the difference in their relative molecular masses

Question 49

At what relative molecular mass do gas particles diffuse the fastest?

Answer 49

Lighter gas particles can travel faster and hence further, therefore the lower its relative mass the faster a gas will diffuse