P6 - Molecules and matter Flashcards
What can the particle model be used to explain?
in chemistry it is called particle theory but effectively the same thing
the different states of matter, and their differences in density
Describe the particles in a solid:
-strong forces of attraction
-held in fixed positions but can vibrate
-fixed shape and volume
Describe the particles in a liquid:
-weaker forces between particles than in a solid
-irregular arrangement, free to move and slide over each other
-shape can change (fills bottom of container)
-volume stays constant
Describe the particles in a gas:
-weakest forces of attraction between particles
-highest average speeds of particles (random motion)
-volume changes (fills container)
What is the change of state from gas to solid?
deposition
RP5 - How would you determine the density of a regular object?
-calculate volume from length/height/width measured using a ruler
-measure mass on mass balance
-use p = m/V
RP5 - How would you find the volume of an irregularly shaped object?
-fill displacement can with water (room temp.) up to the spout
-put beaker at spout of the can
-place object into water slowly, make sure not to splash/drop
-take water from beaker, transfer to measuring cylinder to find volume of water displaced (which is the volume of the object)
The displacement can is also known as the Eureka can
Define internal energy:
total kinetic energy (from individual particle motion) and potential energy (due to position in relation to other particles) of all the particles that make up a system
Doesn’t include GPE or kinetic energy from the motion of the whole structure
What is the difference between specific latent heat of fusion and vaporisation?
-SLH of fusion is solid to liquid
-SLH of vaporisation is liquid to gas
How does specific heat capacity differ from specific latent heat? Give their units:
-SHC is energy needed to heat up 1kg of a substance by 1°C
(J kg⁻¹ °C⁻¹)
-SLH is energy for changing the state of 1kg of a substance but without changing its temperature
(J kg⁻¹)
What does the flat line represent on a temperature time graph? What is happening in terms of energy transfer here?
-a change in state
-work done on the substance is used to increase the internal energy of the substance but not the temperature
-this energy weakens the bonds between the particles
State the formula for the energy required for a change in state:
E = mL
L can be latent heat of fusion or vaporisation
What is Boyle’s law?
-for a fixed mass of gas held at constant temperature:
-pressure x volume = constant
-this indicates pressure and volume are inversely proportional (shown by rearranging the equation)
Explain the changes in pressure if the volume of a container holding gas is increased:
-pressure decreases, because:
-density of gas decreases
-less collisions per unit area on container walls
-normal force acted on the container walls is spread out over a larger area, and as P=F/A, the pressure decreases
What does it mean to “do work” on a gas?
-to do work on a gas means to apply a force to it, like compressing it (decreasing its volume)
-because you have exerted a force on the gas, energy has been transferred to the gas (increasing its internal energy)
