3 - Particle Model of Matter

• What is specific heat capacity?

  
  

  What is the equation?

  - the shc of a substance is the amount of energy required to raise the temperature of 1kg of a substance by 1°C; J/kg°C

  
  

  ∆E = m x c x ∆θ (temperature)
• How are the particles arranged in a solid?

  - tightly packed

  - vibrate in place

  - regular pattern

  - high density

  
• How are the particles arranged in a liquid?

  - closely packed

  - particles can move around

  - not a regular pattern

  - high density

  
• How are the particles arranged in a gas?

  - particles are very far apart

  - not arranged in any pattern

  - particles move at random speeds and random directions

  - low density

  
• What does density tell us?

  - the density of a material tells us the mass for a given volume
• What is the equation for density?

  density = mass/volume (p=m/v)

  (kg/m³) = (kg)/(m³)

  
• How can we determine the density of a regular cube?

  1) Measure the mass using a balance (kg).

  2) Use a ruler to measure the length of one side, cube the value (m³).

  3) Divide the mass by the volume.
• How can we determine the density of an irregular object?

  1) Measure the mass by placing the object on a balance.

  2) Fill a eureka can with water (making sure the water is level with the spout).

  3) Place a measuring cylinder below the spout.

  4) Place the object into the water and measure the volume of displaced water.

  5) Divide the mass by the volume of water displaced.
• What is internal energy?

  - energy stored in a system by the particles

  - sum of the total kinetic energy and potential energy of all the particles that make up a system
• What happens to the internal energy if we heat a solid?

  - if we heat a solid, the internal energy increases (kinetic energy increases) => solid melts to a liquid => liquid boils and turns into a gas
• What happens to the internal energy if we cool a gas down?

  - if we cool the gas down, we reduce the internal energy => gas condenses into a liquid => liquid freezes into a solid
• What is it called when a solid turns directly into a gas? Vice versa?

  solid → gas (sublimation)

  
  

  solid ← gas (deposition)
• How can changes of state be reversed?

  - changes of state are physical changes not chemical changes

  - mass is conserved so no particles are removed or added
• Why is evaporation different to boiling?

  - evaporation is when a liquid turns to a gas but only on the surface of a liquid

  (only particles on the surface have enough energy to turn into a gas)
• On a heating graph, what happens when the line first becomes horizontal?

  - temperature stops increasing and the substance is melting (energy we are putting in is weakening/breaking the forces of attraction between the particles)

  
• What is a substance's melting point?

  - the temperature at whcih the substance melts
• On a heating graph, what happens when the line becomes horizontal for the second time?

  - the substance is boiling
• What is a substance's boiling point?

  - the temperature at which the substance boils
• On a cooling graph, what happens when the line first becomes horizontal? What happens the second time the line becomes horizontal?

  - substance is condensing

  - at the second horizontal line, the substance is melting

  
• What is specific latent heat?

  - the slh of a substance is the amount of energy required to change the state of 1kg of the substance with NO CHANGE IN TEMPERATURE
• What are the 2 types of specific latent heat?

  - fusion (solid to liquid)

  - vapourisation (liquid to gas)
• What is the equation for specific latent heat?

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

  E = mL
• What is gas pressure caused by?

  - the gas particles collide with the walls of the container that the gas is held in => pressure is the total force exerted on the walls of the container
• What are the 2 ways we can increase the pressure?

  - increase the number of collisions per second

  - increase the energy of each collision (increase temperature)
• How does increasing the temperature affect the particles?

  - the temperature of a gas is related to the AVERAGE kinetic energy of the particles

  - increasing the temperature increases the AVERAGE speed at which all the particles are moving
• Why is the pressure high when temperature is high?


  - particles ave higher kinetic energy => more collisions per second & higher energy collisions
• At what angle do particle collisions cause a force?

  - the particle collisions cause a force which acts at RIGHT ANGLES to the walls of the container
• What happens to the gas pressure if we take the same gas and increase the volume of the container?

  
  

  Why is this?

  - if we ↑ volume of the container (while keeping the TEMPERATURE CONSTANT), the pressure ↓

  
  

  (the particles have to travel further before colliding with the walls of the container, reducing the number of collsions per second => reducing pressure)See an expert-written answer!We have an expert-written solution to this problem!
• What is the relationship between the pressure of a gas and the volume?

  pressure is inversely proportional to the volume, p = k/V

  
  

  pV = constant

  (pressure in pascals, Pa) x (volume in m³) = constant
• What is 'work'?

  - the transfer of energy by a force
• Why do some bicycle pumps get warm when we use them to inflate a tyre?

  - we are doing work (transfering energy when we apply the force) on the gas, increasing its internal energy (which is kinetic energy + potential energy)