particle model

Question 1

the simple kinetic theory model to explain the different states
of matter (solids, liquids and gases) in terms of the movement

Answer 1

• heating a liquid transfers extra energy into the particles kinetic energy store so they move faster (boiling)
• heating a solid makes particles vibrate faster from extra energy until the forces between them are overcome and the particles move around (melting)

Question 2

simple kinetic theory model to explain the different states
of matter (solids, liquids and gases) in terms of the arrangement of particles

Answer 2

• particles of a substance in each state are the same
• the arrangement and energy of the particles are different
• reversing a change of state makes the particles go back to how they were before

Question 3

density equation

Answer 3

density (kg/m cubed) = mass (kg) / volume (m cubed)

Question 4

Core Practical: Investigate the densities of solid and liquids

Answer 4

• need mass and volume
  -> mass using mass balance
  -> volume using measuring cylinder
• pour in liquid, measure mass of cylinder (difference in mass is equal to the mass of the liquid)
• if object is not regular shape use a density bottle

Question 5

Core Practical: Investigate the densities of solid and liquids using a DENSITY BOTTLE

Answer 5

1. measure mass with mass balance
2. fill bottle with liquid of known density (ex water)
3. place stopper and let bottle dry
4. measure bottle’s mass
5. empty the bottle and place object into the density bottle
6. repeat 2 and 3
7. measure mass of the bottle
8. calculate the volume of displaced water
9. calculate density

Question 6

how to find the volume of displaced water when using a density bottle to find the density of something

Answer 6

• mass of displaced water = m2 - (m3 - m1)
• the 2,3,1 are not squares…
• knowing the density of the water, use V = m / p to find volume displaced (this equals the volume of the object)

Question 7

Explain the differences in density between the different states of
matter in terms of the arrangements of the atoms or molecules

Answer 7

• solids are more dense
• density decreases from solid -> liquid -> gas
• as the mass stays the same
• volume changes as particles have more energy to overcome

Question 8

describe that changes of state are physical changes

Answer 8

• changes of state are physical changes not chemical changes because the material recovers its original properties if the change is reversed

Question 9

is mass conserved during changes of state

Answer 9

yes

Question 10

Explain how heating a system will change the energy stored
within the system and raise its temperature or produce changes
of state

Answer 10

• the energy the particles have increases
• vibrate more
• temperature increases or system changes state

Question 11

what is the energy in a substances’ thermal energy store held by

Answer 11

its particles in their kinetic energy stores

Question 12

define specific heat capacity

Answer 12

energy required to raise the temperature of 1kg of a substance by 1 degree

Question 13

define specific latent heat

Answer 13

energy to change the state of 1kg of a substance without a change in temperature

Question 14

equation for working out specific heat capacity

Answer 14

• change in thermal energy (J) = mass (kg) * (specific heat capacity (j/kg degree c) * change in temperature (degree c)

Question 15

equation to work out specific latent heat

Answer 15

thermal energy for a change of state (J) = mass (kg) * specific latent heat (J/kg)

Question 16

Explain ways of reducing unwanted energy transfer through
thermal insulation

Answer 16

• thermal energy transfers out of a system and so is wasted
• thermal insulators reduce amount of energy lost
  -> as it is a poor thermal conductor
• use reflective coating to reflect IR radiation (heat) back into the system

Question 17

Core Practical: Investigate the properties of water by
determining the specific heat capacity of water

Answer 17

1. measure mass of insulator container using mass balance
2. fill container with water and remeasure mass
3. set up experiment (joulemeter connected to electric immersion heater (with power supply), have an insulating container with water and a thermometer in it)
4. measure temperature of water and then turn on power
5. when temperature increases stop the experiment and record energy on joulemeter and the increase in temperature
6. use equation
7. repeat

Question 18

Core Practical: obtaining a
temperature-time graph for melting ice

Answer 18

1. fill beaker with crushed ice
2. place thermometer into ice beaker and record the temperature
3. heat beaker using Bunsen burner
4. record temperature and the current state of the ice every 20 seconds
5. continue this process until the water boils
6. plot graph of temperature against time

Question 19

what a temperature-time graph for melting ice looks like:

Answer 19

the graph should go up (ice (solid)) then stop (melting) then go up (water (liquid)) then stop (boiling/ evaporating) then go up (steam (gas))

Question 20

what a temperature-time graph for condensing and freezing looks like:

Answer 20

starts at the top of the y axis, goes down (gas) stops at boiling point, goes down (liquid) stops at melting point, goes down to solid
* the parts where it stops show a change in temperature

Question 21

Explain the pressure of a gas in terms of the motion of its
particle

Answer 21

• pressure produces a force at right angles to any surface
• particles collide with wall and change velocity
• so change momentum during collision
• exert a force on the wall

Question 22

explain the effect of changing the temperature of a gas on the velocity of its particles and hence on the pressure produced by a fixed mass of gas at constant volume (qualitative only)

Answer 22

• increased temperature means more energy given to particles
• thermal energy is transferred to kinetic
  -> particles move faster
  -» COLLISIONS OCCURE MORE FREQUENTLY
  -»> particles hit wall with greater impact
  -»» so pressure increases

Question 23

describe the term absolute zero (-273 degrees) in terms of the lack of movement of particles

Answer 23

• nothing can exist at a colder temperature than this
• particles at this temperature had NO ENERGY do they do not vibrate at all
• so are still

Question 24

convert between kelvin and Celsius scales

Answer 24

• degrees to kelvins you add 273
• kelvins to degrees celsius you subtract 273