TOPIC 5 SOLIDS, LIQUIDS AND GASES

Question 1

what is the equation for density?

Answer 1

density = mass / volume

Question 2

what are the units for density ?

Answer 2

grabs per cubic centimetre - g/cm3

or

kilograms per cubic metre - kg/m3

Question 3

what does it mean if a solid object floats on the surface of a liquid

Answer 3

it has a lower density than the fluid

Question 4

what does the density depend on?

Answer 4

the density of an object depends on what it’s made of- density doesn’t vary with the shape of size

Question 5

what does the average density determine

Answer 5

whether the object floats or sinks

Question 6

what is an experiment to demonstrate density

Answer 6

you can measure the volume by completely immersing the object into a measuring container of water.

the amount the volume reading on the container increases by when you add the object to the water is the volume of the object

this only works for objects denser than water though

Question 7

what is density?

Answer 7

Density is the mass per unit volume- the measure of compactness of a substance. It relates the mass off a substance to how much space it takes up.

Question 8

what is the equation for pressure?

Answer 8

pressure = force / area

Question 9

what is pressure ?

Answer 9

pressure is the force acting per unit area of a surface. Pressure is a measure of the force being applied to the surface of something. It relates how much force is being applied to an object (N) to the area that it is applied over (in m2). Pressure is measured in pascals (Pa) or kilopascals (kPa). 1Pa=1N/m2

Question 10

describe how pressure works

Answer 10

when force is concentrated on a smaller area creates a larger pressure, but with a larger area, you get a smaller pressure.

Question 11

describe how pressure works in snowshoes in snow

Answer 11

they have a large surface area and therefore there is less force concentrated into the ground

Question 12

describe how pressure affects stiletto heels marking floors

Answer 12

there is a small surface area and therefore more force is concentrated into the ground

Question 13

describe how pressure works when walking on pebbles and sand

Answer 13

even though ther is a small surface area, the individual grains are combined repay her than the individual pebbles, so there is less pressure

Question 14

how is it possible to lie on a bed of nails

Answer 14

it is possible because the total contact is spread out so there is less pressure applied

Question 15

convert 1m2 to cm2 and mm2

Answer 15

1m2 = 10,000cm2 = 1,000,000mm2

Question 16

how do you work out the pressure difference in liquids and gases

Answer 16

pressure difference = height x density x gravity (10)

Question 17

what is pressure difference for liquids and gases?

Answer 17

pressure in liquids and gases depends on density. It is the difference in pressure between two points in a liquid or gas. It depends on the height difference (m) and the density (kg/m3) of the substance. Gravity also has an affect too - g is the acceleration due to gravity which is about 10m/s2

Question 18

describe pressure for gases and liquids

Answer 18

in gases and liquids at rest, the pressure at any point acts equally in all directions. in gases and liquids, the pressure increases with depth. The pressure is higher at the bottom of the sea than the surface and it is lower high up in the atmosphere at hand close to earth

Question 19

describe what happens with a water in a bag with holes

Answer 19

Pressure moves in all directions. It is the same throughout the water so water jets act in all directions. This is because when the water molecules move, they transmit a force to all the molecules next to them.

Question 20

describe what happens on a diver (bottle experiment description)

Answer 20

the conpression on the bottle increases the pressure in the water. this compresses the air inside the diver. the air now displaces less water so there is less is less upthrust acting on the diver. the diver takes in more water so the weight increases

Question 21

describe what happens with pressure on a spouting can

Answer 21

as the depth increases, the weight of the water increases so the is more pressure lower down. this increase in pressure which push the water jet out at a greater velocity

Question 22

why do divers masks not break at great depth

Answer 22

the same pressure and force is Cting inside the mask so the resultant force is 0

Question 23

describe what happens with atmospheric pressure with a card in a water beaker

Answer 23

the atmospheric pressure pushes up the card and holds water in place. due to the atmospheric pressure being greater than the water.

Question 24

describe how atmospheric pressure affects a bottle and hot water

Answer 24

after heating, the bottle is full of hot air. as the air cooled, fewer particles collide with the inside of the bottle. this decreases pressure inside the bottle and reduces the density. atmospheric pressure outside the bottle is bigger is bigger so the bottle collapses

Question 25

describe how atmospheric pressure affects a ruler and newspaper

Answer 25

air pressure is pushing down on the entire sheet of the newspaper (with a large surface area) which means it’s difficulty to flip the ruler.

Question 26

describe how atmospheric pressure affects a bottle and vaccum pump

Answer 26

the air is removed from the bottle which reduces the pressure inside. the atmospheric pressure is larger on the outside and therefore compresses the bottle

Question 27

describe how atmospheric pressure affects the Magdeburg hemispheres

Answer 27

air is removed from the inside of the hemispheres. the atmospheric pressure is greater than the pressure inside. hence there is a large force pushing on the spheres

Question 28

describe solids

Answer 28

In solids, there are…

• strong forces of attraction holding it together in a fixed regular lattice arangement
• definite shape and volume
• their particles vibrate in their positions
• when heated, their particles vibrate faster and allow the to expand

Question 29

descibe liquids

Answer 29

in liquids, there are…

• weak forces of attraction between the the particles
• randomly arranged (but they tend to stay closely together.
• the dont have a fixed shape but do have a fixed volume.
• their particles are constantly moving but when heated the expand

Question 30

describe gases

Answer 30

in gases, there are…

• very weak forces of attraction
• move far apart from each other
• travel in straight lines between collisions
• constantly moving randomly
• don’t have definite shape of volume (they fill any container)
• when heated their particles move faster which means they expand or their pressure increases

Question 31

what happens to the particles when a substance is heated

Answer 31

the particles gain more kinetic energy - (vibrate faster in solids)

Question 32

explain what happens to the particles when a substance changes state

Answer 32

the state of matter depends on 3things temperature, pressure and material- the particles gain enough energy (potential energy) to break free of their inter-molecular bonds, separation increases at a constant temperature I.e. volume increases, volume of gas is about 1000x bigger than the volume of solids or liquids

Question 33

what are the main assumptions for the kinetic theory of matter?

Answer 33

every material is made up of small particles (molecules). the sizes of particles are different for different materials. the particles are very hard (incompressible) but the separation between particles can change. the particles are always moving p (high per temp=faster). particles at the same temperature have the same kinetic energy so heavier particles move more slowly.

Question 34

how is evaporation different to boiling?

Answer 34

in evaporation- it is gradual vaporisation…. it eventually turns to a gas overtime as some molecule have enough energy t escape the attractive forces. these molecules change to a gas and leave.

in boiling - it is a rapid vaporisation …. all the particles have sufficient energy to escape.

Question 35

what is the Brownian motion and what does it illustrate

Answer 35

it is the constant motion of smoke particles seen with a microscope- caused by the collisions in the air which transfer energy. evidence of the random motion of air particles

Question 36

give an example of the Brownian motion

Answer 36

the constant movement of smoke particles viewed under a microscope.

Question 37

explain how the Brownian motion supports the idea that matter is made from tiny particles in continuous motion

Answer 37

in liquids and gases, particles have no fixed arrangement (irregular) and are free to move around. small particles hit larger particles which shows the random movement

Question 38

Describe the particle arrangement in solids

Answer 38

Particles of solids have a fixed regular arrangement. The particles are not free to move however vibrate in their positions. If heated there is more kinetic energy and therefore vibrate faster

Question 39

Describe the particle arrangement in liquids

Answer 39

The particles in liquids had definite volume but no definite shape. Their particles have weak attraction so a free to move past each other

Question 40

Describe the particle arrangement in gases

Answer 40

They do not have definite shape but do have definite volume. They are free to move in straight lines between collisions so have a larger space between the particles. (more KE)

Question 41

Explain what causes gas pressure in a sealed container

Answer 41

The particles in gases move quickly in all directions but bump into the walls of the container. If the temperature is above 0, particles have more kinetic energy. When the particles collide with the container, it exerts a force and this force acts over and area so the pressure increases. (p=fa)

Question 42

Explain what happens to the pressure of a gas when heated

Answer 42

Increasing the temperature gives more kinetic energy to the particles. Collisions are more frequent with the walls and other particles and with a greater force. This increases pressure (pressure is proportional to its absolute temperature).

Question 43

Explain the term ‘absolute temperature’

Answer 43

It’s lowest possible temperature at which point the atoms of a substance transmit no thermal energy (-273degrees c = 0Kelvin)

Question 44

Describe and explain some applications of cooling materials to a very low temperature

Answer 44

Reduce the resistance of electrical components e.g MRI or LHC

Levitation and transport

Question 45

What is the relationship between average kinetic energy of a molecule of gas and temperature

Answer 45

The average kinetic energy of a molecule of gas is directly proportional to its absolute temperature

Question 46

CQ

in a sample of gas, oxygen (O2) and hydrogen (H2) molecules are both at the same temperature. The speed of oxygen molecules is 250ms-1.
Use Mr of O2 and H2

How fast are the hydrogen molecules moving?

Answer 46

KE = 0.5mv2

they are both at the same temperature so the average KE is the same

KE = 0.5 x 32 x (250)2 = 1,000,000

0.5 x 2 x v2 - square root 1000000 / 0.5 x 2
= 1000ms-1

Question 47

What is Boyle’s law

Answer 47

It states that the volume of a fixed mass of a gas is inversely proportional to its pressure provided that the temperature remains constant

Question 48

Describe how Boyle’s law is explained using the kinetic model

Answer 48

The temperature is constant so the particles have constant kinetic energy. As the volume of the gas decreases, the particles are more likely to collide to the container walls (as they have less distance to travel). This increased the rate of collisions and leads to an increase in pressure

Question 49

Describe the pressure law

Answer 49

The pressure law states that the pressure of a fixed mass of a gas and is proportional to its absolute temperature provided they volume remains constant