the particle model - topic 13

Question 1

what is density

Answer 1

a substances mass per unit volume

Question 2

density =

Answer 2

mass/volume

Question 3

how to measure density of a liquid

Answer 3

1. put measuring cylinder on balance and zero the
   balance
2. add 10ml of liquid and record mass
3. add 10ml and record mass and volume
4. repeat and find average then use density = mass/vol

Question 4

how to measure density of a solid

Answer 4

1. measure object’s mass with balance
2. fill eureka can with water and let it drain
3. place empty measuring cylinder under spout
4. put solid in can and measure vol of water displaced
5. density = mass/vol

Question 5

why are solids solid

Answer 5

strong forces of attraction hold the particles close together in a fixed, regular lattice and there is not much energy in KE stores so they vibrate about fixed positions

Question 6

why are liquids like they are

Answer 6

they have weaker forces of attraction between particles and some are able to move past each other. They also have more energy in KE stores so they move more randomly

Question 7

why are gases like they are

Answer 7

they have no forces of attraction and have more energy in KE stores and so are free to move in random directions

Question 8

kinetic theory of matter

Answer 8

a theory explaining how particles in matter behave by modelling these as tiny balls

Question 9

internal energy

Answer 9

the total energy that a systems particles have in their KE and potential energy stores

Question 10

why do particles in a system vibrate and move around

Answer 10

they have energy in their KE stores

Question 11

more energy in KE store =

Answer 11

faster movement

Question 12

further apart particles =

Answer 12

more energy in this store

Question 13

more energy in thermal store =

Answer 13

higher temperature

Question 14

what does temperature measure

Answer 14

how much energy is in thermal store

Question 15

when temp increases …..

Answer 15

the particles vibrate and move around faster but the positions of the particles relative to each other don’t change

Question 16

cooling a system does what to energy

Answer 16

reduces energy of the particles

Question 17

what is the coldest anything can ever get

Answer 17

-273 degrees celsius

Question 18

what is absolute zero

Answer 18

as little energy in their KE stores as possible

Question 19

how to convert temp in C to temp in K

Answer 19

temp in C + 273

Question 20

how to convert temp in K to temp in C

Answer 20

temp in K - 273

Question 21

how to go from solid to liquid

Answer 21

melting

Question 22

how to go from liquid to solid

Answer 22

freezing

Question 23

how to go from solid to gas

Answer 23

sublimating

Question 24

how to go from liquid to gas

Answer 24

boiling

Question 25

how to go from gas to liquid

Answer 25

condensing

Question 26

what happens to particles and forces when a system is heated and changes state

Answer 26

energy is transferred to potential energy store, particles move apart and forces get weaker

Question 27

why is mass conserved during changes of state

Answer 27

because the number of particles remains the same, only the properties are changing

Question 28

what is specific heat capacity

Answer 28

the amount of energy needed to raise the temperature of 1kg of a substance by 1 degrees celsius

Question 29

change in thermal energy =

Answer 29

mass x specific heat capacity x temperature change

Question 30

investigating specific heat capacity

Answer 30

1. place container on balance and fill with water and record mass 2. connect power supply to immersion heater and ammeter which is also connected to heater and put thermometer in water 3. measure initial temp and set pd of power supply 4. start the stop watch 5. current should not change as temp increases 6. once temp increases by 10C, stop stopwatch and heater 7. Use E=i x v x t to work out energy supplied by heater 8. SHC equation and calculate the specific heat capacity

Question 31

what is specific latent heat

Answer 31

the amount of energy needed to change 1kg of a substance from one state to another without changing its temperature

Question 32

specific latent heat of fusion

Answer 32

changing state between solid and liquid

Question 33

specific latent heat of vaporisation

Answer 33

changing state between a liquid and a gas

Question 34

thermal energy for change of state =

Answer 34

mass x specific latent heat

Question 35

how do we investigate changing matters of state

Answer 35

1. fill beaker with crushed ice + place thermometer in 2. set up equipment ( beaker with thermometer on bunsen burner) 3. measure initial temp 4. start stop watch and turn on bunsen burner 5. every 20s, record temp and state of ice 6. continue until ice melts and water boils 7. turn off stop watch and bunsen burner and plot results

Question 36

as gas particles move at high speeds

Answer 36

they collide into each other and the walls of the container they are in and when they collide with a surface they exert a force on it.

Question 37

as temp increases

Answer 37

faster movement and therefore more collisions

Question 38

what happens to gas pressure and force as temp increases

Answer 38

increase in net force and gas pressure

Question 39

what happens to the pressure if temp is constant and there is increasing volume

Answer 39

particles get more spread out and hit walls of container less and lowers gas pressure

Question 40

how are pressure and volume related

Answer 40

they are inversely proportional

Question 41

what happens to the volume of gas if internal and external pressure is equal

Answer 41

the volume of the gas and container is constant

Question 42

how does doing work affect temp

Answer 42

it increases its internal energy which can increase its temp

Question 43

pressure 1 X volume 1

Answer 43

pressure 2 X volume 2

Question 44

how does heating a system change the energy within the system

Answer 44

heating a system transfers energy to its particles, so heating a system always increases its internal energy of the system which also leads to an increase in temperature or change in state

Question 45

how do you reduce unwanted energy transfer

Answer 45

wrap the container in a thermally insulating material and place it on an insulating surface.

Question 46

why does thermal insulation reduce unwanted energy transfer

Answer 46

thermal insulators reduce the rate at which energy is transferred by heating, which means less energy is transferred to the thermal energy stores of the surrounding.

Question 47

what is the effect of changing the temperature of a gas

Answer 47

the hotter it is, the fasters its particles move. Faster particles and more collisions with the walls of the container in a given time both lead to an increase in net force and gas pressure

Question 48

what is the effect of changing the volume of a gas

Answer 48

if the temperature is kept constant, increasing the volume of a gas means the particles get more spread out so the particles hit the walls of the container less often and gas pressure decreases

Question 49

how can gases be compressed or expanded by pressure change

Answer 49

if a container can easily change its size, then any change in these pressures will cause the container to compress or expand

Question 50

why is density of a substance highest when a solid

Answer 50

the particles are packed close together - there is a lot of mass in a given volume and as density = mass x volume the density is high

Question 51

why are liquids less dense than solids

Answer 51

because they have fewer particles in a given volume

Question 52

why are gases less dense than liquids and solids

Answer 52

because gases have particles spaced far apart, a substance in gas form is less dense