SP14 - Particle Model ✓ Flashcards Preview

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Flashcards in SP14 - Particle Model ✓ Deck (26)
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SP14a - What does kinetic theory state?

Everything is made of tiny particles


SP14a - Describe the properties of a solid

  • Rigid
  • Fixed shape
  • Fixed volume
  • Cannot be compressed


SP14a - Describe the properties of a liquid

  • Not Rigid
  • No fixed shape
  • Fixed volume
  • Cannot be compressed(ish)


SP14a - Describe the properties of a gas

  • Not Rigid
  • No fixed shape
  • No fixed volume
  • Can be compressed


SP14a - What happens when a substance changes state? (In terms of particles)

  • The particles change their arrangement
  • This leads to a change in density
  • The mass is conserved as the amount of particles remains
  • This is a physical change as it can be reversed and no new substances are formed


SP14a - How does the density of a substance change between states and what is the exception?

  • Generally, as substances go from solid → liquid → gas, they become less dense
  • This is because the particles become more spread out meaning there are less in a certain volume
  • Water is the exception to this as ice is less dense than liquid water


SP14a - What is density inc. formula?

Density is a measure of how many particles are packed in a space

Density(g/cm³) = mass(g) ÷ volume(cm³)

(ρ = m x V)


SP14a CP - How do you find the density of an irregularly shaped object?

  • Set an electronic balance to 0 then place the object on it and record the mass
  • Set up a displacement can leading into an empty measuring cylinder and fill the can with water
  • Place the object in the can. If it floats, then push it down till it is just under the surface of the water
  • Read the value for the volume of water in the measuring cylinder (from the bottom of the meniscus)
  • This is the volume of the object. Do mass/volume to find the density


SP14b - What is thermal energy?

The energy stored in the movement of particles that has been transferred to the system by heating


SP14b - What is temperature?

A measure of the average speed/movement of the particles in a substance


SP14b - What is specific heat capacity?

The amount of energy required to increase the temperature of 1 kg of a substance by 1°C (The diagonal lines of a heating curve)


SP14c - What is the formula for specific heat capacity?

ΔQ = m x c x Δø

Change in energy(J) =

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


SP14b - What is specific latent heat?

  • The amount of energy required to change the state of 1kg of a substance (The horizontal parts of a heating curve)
  • This energy is given out when the doing the opposite state changes are equal to how much it takes
  • (energy needed for evaporating = energy released form condensing)


SP14c - What is the formula for specific latent heat?

Q = m x L

Energy = mass x Specific latent heat


SP14b - Describe the appearance of a heating curve describing what is happening

  • Time on x-axis temperature on y-axis
  • There will be a diagonal line going up steadily upwards
  • Eventually it will plateau and be a horizontal line for a bit
  • It will then continue to rise diagonally then plateau and then rise once more 
  • The diagonal lines are where energy is transferred and stored as thermal energy and increasing the temperature
  • During the plateaus, the energy is being used to overcome the forces that hold the molecules together resulting in changes of state


SP14d - What is the temperature of a gas and how can it increase?

  • A measure of the average kinetic enegry of the particles in the gas
  • By heating it up (providing thermal energy) the particles will start to move faster meaning a higher temperature


SP14d - Why does an increase in temperature lead to an increase in gass pressure (for a fixed mass of gas)?

  • A higher temperatures means that the particles in the gas are moving fatser.
  • This means that they will have more frequent collisions with the walls of their container.
  • This means that the force exerted on the container is higher leading to a higher temperature.


SP14d - What is the unit for pressure?

pascals (Pa)

[where 1 Pa = 1 N/m²]


SP14d - What is absolute zero?

  • Once the temperature of a gas has reduced to -273°C (or 0K) then the particles in the gas have a pressure of 0 meaning they aren't moving.
  • This is only theoretical as gases would normally condense to a liquid once reaching this low a temperture


SP14d - What is the kelvin scale and how do you convert between celcius to kelvin v.v?

  • The kelvin scale has the same intervals as celcius but 0 K is equal to absolute zero (-273°C)
  • To convert K - °C  - 273 and °C - K + 273



SP14d - Describe the relationship between kelvin and the avergae kinetic energy of gas

Directly proportional


SP14e - What is gas pressure?

When gas particles hit a surface, they produce a net force acting at right angles to the surface. We detect this as gas pressure


SP14e - Why does decreasing the volume of gas (at a fixed mass and temperature) increase the pressure?

  • Inside a container, the pressure acts at right angles to the walls
  • If the same number of particles are in a smaller space, they will hit the walls of the container more often
  • This means the force on the walls increases. We detect this as a higher pressure


SP14e - What equation links pressure and volume for a fixed mass and temperature?

  • P1 x V1 = P2 x V2
  • This means that an increase in pressure or volume will cause a decrease of the other by the same proportion
  • They are inversely proportionate



SP14e - Why does pumping a bike tyre up increase the pressure of the pump?

  • More air is forced into the typre when you pump it
  • This increases the number of gas particles in a fixed volume
  • As a result, there is an increase in the frequency of collisions between gas particles and the (inner) surface of the tyre
  • This leads to more force exerted on and thus an increased pressure in the tyre


SP14e - Why does the temperature of a tyre increase as you pump it?

  • Each time you push the pump handle, the force is transferring energy to the gas inside the pump (This is work done)
  • As the piston of the bike pump moves, the speed (KE) of any particles inside the particles increases as they bounce off it
  • This means that the average speed of the particles has increased and we detect this as an increase in temperature