particle model Flashcards
topic 14
the simple kinetic theory model to explain the different states
of matter (solids, liquids and gases) in terms of the movement
- 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)
simple kinetic theory model to explain the different states
of matter (solids, liquids and gases) in terms of the arrangement of particles
- 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
density equation
density (kg/m cubed) = mass (kg) / volume (m cubed)
Core Practical: Investigate the densities of solid and liquids
- 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
Core Practical: Investigate the densities of solid and liquids using a DENSITY BOTTLE
- measure mass with mass balance
- fill bottle with liquid of known density (ex water)
- place stopper and let bottle dry
- measure bottle’s mass
- empty the bottle and place object into the density bottle
- repeat 2 and 3
- measure mass of the bottle
- calculate the volume of displaced water
- calculate density
how to find the volume of displaced water when using a density bottle to find the density of something
- 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)
Explain the differences in density between the different states of
matter in terms of the arrangements of the atoms or molecules
- 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
describe that changes of state are physical changes
- changes of state are physical changes not chemical changes because the material recovers its original properties if the change is reversed
is mass conserved during changes of state
yes
Explain how heating a system will change the energy stored
within the system and raise its temperature or produce changes
of state
- the energy the particles have increases
- vibrate more
- temperature increases or system changes state
what is the energy in a substances’ thermal energy store held by
its particles in their kinetic energy stores
define specific heat capacity
energy required to raise the temperature of 1kg of a substance by 1 degree
define specific latent heat
energy to change the state of 1kg of a substance without a change in temperature
equation for working out specific heat capacity
- change in thermal energy (J) = mass (kg) * (specific heat capacity (j/kg degree c) * change in temperature (degree c)
equation to work out specific latent heat
thermal energy for a change of state (J) = mass (kg) * specific latent heat (J/kg)
Explain ways of reducing unwanted energy transfer through
thermal insulation
- 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
Core Practical: Investigate the properties of water by
determining the specific heat capacity of water
- measure mass of insulator container using mass balance
- fill container with water and remeasure mass
- set up experiment (joulemeter connected to electric immersion heater (with power supply), have an insulating container with water and a thermometer in it)
- measure temperature of water and then turn on power
- when temperature increases stop the experiment and record energy on joulemeter and the increase in temperature
- use equation
- repeat
Core Practical: obtaining a
temperature-time graph for melting ice
- fill beaker with crushed ice
- place thermometer into ice beaker and record the temperature
- heat beaker using Bunsen burner
- record temperature and the current state of the ice every 20 seconds
- continue this process until the water boils
- plot graph of temperature against time
what a temperature-time graph for melting ice looks like:
the graph should go up (ice (solid)) then stop (melting) then go up (water (liquid)) then stop (boiling/ evaporating) then go up (steam (gas))
what a temperature-time graph for condensing and freezing looks like:
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
Explain the pressure of a gas in terms of the motion of its
particle
- 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
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)
- 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
describe the term absolute zero (-273 degrees) in terms of the lack of movement of particles
- 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
convert between kelvin and Celsius scales
- degrees to kelvins you add 273
- kelvins to degrees celsius you subtract 273
