P1.2 - Change of State

Question 1

define density

Answer 1

mass per unit volume

Question 2

what is the equation for density?

Answer 2

density = mass(kg)/ volume (m3)

Question 3

what three factors does density depend on?

Answer 3

• mass of material
• particle arrangement
• volume

Question 4

explain why the density of a substance in that the solid state is greater than the density of the same substance in the liquid state

Answer 4

• there are more particles in the same volume (solid)
• and so the mass is greater
  in a liquid, there are less particles in the same volume
  so the mass is less
  (leading to a higher density)

Question 5

why do substances in different matters have different densities?

Answer 5

they have different arrangement of particles

Question 6

define temperature

Answer 6

the average kinetic energy per particles

Question 7

is temperature a measure of heat energy?

Answer 7

no, particles do not know heat energy, only kinetic

Question 8

why does your hand not burn if a spark lands on you?

Answer 8

• the mass of the sparkler is very small
• the total energy stored by all the particles is small
• energy is so little, does not burn you

Question 9

what does the energy in a thermal store depend on?

Answer 9

• the arrangement of the particles

- how fast they are vibrating or moving

Question 10

what does the energy needed to raise the temperature of an object depend on?

Answer 10

• type of material
• the mass of the material
• temp rise

Question 11

what is specific latent heat?

Answer 11

the energy transferred when 1kg of a substance changes state

Question 12

what equation is required to calculate the change in thermal energy? - when temp change

Answer 12

mass (kg) x specific heat capacity (j/kg C) x change in temperature (C)

Question 13

what does specific heat capacity show?

Answer 13

the amount of energy needed to increase the temperature of 1kg of the substance by 1oC

Question 14

why is water good to use in radiators?

Answer 14

because it has a high specific heat capacity, making it resistant to temperature change (so would have a lot of energy to transfer)
- almost 4200J/kg

Question 15

why are saucepans made with low specific heat capacities?

Answer 15

• as they need to heat up quickly to heat the food

Question 16

where does the energy from tropical storms come from?

Answer 16

• water vapour condensing and transferring energy to its surroundings

Question 17

explain why there is no temperature increase while water is boiling

Answer 17

• energy transferred is used to break attractive forces between the water molecules
• internal energy is increasing but temp is not

Question 18

what is the specific latent heat of fusion?

Answer 18

(melting)
- the energy transferred when 1kg of a substance changes from the solid state to the liquid state (or vise versa)
WITHOUT CHANGING TEMPERATURE

Question 19

what is the specific latent heat of vaporisation?

Answer 19

the energy transferred when 1kg of a substance changes from liquid to gas WITHOUT CHANGING TEMPERATURE

Question 20

what is the equation to calculate the thermal store for a change in state?

Answer 20

energy store (J) = mass (kg) x specific latent heat (J/kg)

Question 21

what are the similarities and differences between specific latent heat and specific heat capacity?

Answer 21

• they both involve energy changes for 1kg of a substance
• latent heat is about change in state
• heat capacity is about change of temperature

Question 22

what is the law of displacement?

Answer 22

an object completely submerged in a fluid will replace an amount of fluid to its own volume

Question 23

what is the force that keeps an object afloat?

Answer 23

upthrust

Question 24

what is the equation to calculate specific heat capacity?

Answer 24

change in internal energy / mass x change in temperature

Question 25

when a substance changes state, where does the latent heat go?

Answer 25

to create or weaken bonds, rather than transfer kinetic energy to the particles

Question 26

what does it mean when a term starts with ‘specific’?

Answer 26

means it is measured in kilograms (standardises)

Question 27

what are the units of latent heat of vaporisation?

Answer 27

J/Kg

Question 28

What happens to the energy supplied during a change of state at both the melting and boiling points?

Answer 28

kinetic energy remains constant while the potential energy increases

Question 29

which two stores of energy are added together to calculate the internal energy?

Answer 29

kinetic store + chemical store

Question 30

how does heating a system affect energy stored (in terms of temperature and state)?

Answer 30

• increase energy within system
• raises temperature, but remains in same state
• remains same temperature, changes state
• make chemical reactions occur

Question 31

name for when solids turn straight into gases

Answer 31

sublimination

Question 32

unit for specific heat capacity?

Answer 32

J/Kg°C

Question 33

what does specific heat capacity show?

Answer 33

how resistant a material is to temperature change