Topic 3- Particle model of matter Flashcards
What are density units?
kg/m³
Required practical steps (density of regular shaped objects)
- Measure mass on a balance
- Measure length of sides and multiply to find the volume
- Use the equation to find density
Required practical steps (density of irregular shaped objects)
- Measure mass on a balance
- Fill large measuring cylinder or a displacement/eureka can
- Volume of displaced water= volume of object
- Use equation to find density
Required practical steps (density of liquids)
- To find volume, put in measuring cylinder
- Find mass on balance, take away mass of empty cylinder
- Use equation to find density
Describe the particle arrangement of a solid
Tightly packed in a regular arrangement.
Particles can only vibrate on the spot
Describe the particle arrangement of a liquid
Close together, but with an irregular arrangement.
They can flow over each other
Describe the particle arrangement of a gas
Separated, with no regular arrangement.
Particles can move freely
What is always conserved when a substance undergoes a change of state?
Mass
What are the particle model’s limitations?
Only 2D
We don’t see forces between the particles
We don’t see the movement of the particles
How does a change of state differ from a chemical change?
In a change of state, the material can return to having its previous properties if the change is reserved
What is sublimation?
When a solid changed into a gas without passing through a liquid state
When water boils in an open pan, why does the mass of the pan of water appear to decrease?
Some of the water will evaporate and turn into water vapour
This will leave the pan meaning the mass of the pan will decrease.
The mass of the whole system however, remains constant
Explain the processes involved when a bathroom mirror mists up
Hot water evaporates to form water vapour
This water vapour lands on the cooler mirror
The vapour condenses and returns to liquid state on the mirror’s surface
What is internal energy?
Energy which is stored by particles (atoms and molecules) within a system
Kinetic energy + potential energy of particles
How does heating affect the energy of a substance?
Heating transfers energy to the substance
It increases the energy of the particles that make up the substance
What two things can heating a substance do?
Raise its temperature
Change the state of the substance
What three factors determine the temperature change of a system?
Mass of substance being heated
Type of material (Specific heat capacity)
Energy inputted into the system
Define specific heat capacity
The amount of energy needed to increase the temperature of 1kg of a substance by 1 degree celcius
Define specific latent heat
The amount of energy needed to change the state of 1kg of a substance without a change in temperature
Define specific latent heat of fusion
The energy required to change 1kg of a substance from solid state to liquid state without a change in temperature
Define specific latent heat of vaporisation
The energy required to change 1kg of a substance from liquid state to gas state (vapour) without a change in temperature
Describe the motion of molecules in a gas?
They are in constant random motion
What factor affects the average kinetic energy of gas molecules?
The temperature of the substance
The higher the temperature, the higher the average kinetic energy of the molecules
What effect does increasing temperature have on the pressure of a gas when held at constant volume?
Pressure of the gas will increase as the temperature increases
Why does pressure increase as temperature increases (at a constant volume)?
Kinetic energy of molecules increases
Collisions between molecules become more frequent
Greater rate of change of momentum
Greater force and therefore pressure
If Gas A is at a low pressure and gas B is at a high pressure, what can be said about the rate of collisions in each gas?
There are more collisions per second in gas B than in gas A
The rate of collisions is higher in B
Describe the force that the pressure of a gas exerts on the walls of its container
The net force acts at right-angles to the container’s surface
The force increases as pressure increases
Explain how increasing the volume of a gas results in a decrease of pressure
Molecules become more spread out and so time between collisions increases
This reduced the rate of collisions
Rate of change of momentum decreases, resulting in a lower pressure
What unit is used for pressure?
Pascals (Pa)
What increases when you do work on a gas?
The internal energy of the gas
This can also lead to an increase of temperature
Why does the temperature of air inside a bike pump increase when it is pumped?
Work is done on a gas when it is compressed
Doing work on a gas increases its internal energy, so also increases the average kinetic energy of the molecules
Temperature increases with an increase of average kinetic energy
What can be said about the product of pressure and volume for a fixed mass of gas at a constant temperature?
It is constant
p V = constant
Explain how the internal energy of the water changes as it is heated
The kinetic energy of the particles increases
Which increases the internal energy of the water
A student measure the mass of boiling water that was turned into steam in five minutes
Explain how the student could use this information to estimate the power output of the Bunsen burner in watts
Energy given to water E = mL with quantities defined
power output (of Bunsen burner) = energy transferred (to water)/time
power output = change in mass × specific latent heat time
Time should be converted to seconds or use a time of 300 seconds
A student measured the temperature stearic acid over 5 minutes to investigate the change of state from liquid to solid
After having become a solid, the temperature still decreased
Why?
Stearic acid is still hotter than the surroundings
Temperature will decrease until acid becomes room temperatures
Explain, in terms of the particles, why gases are easy to compress
Large gaps between particles
So it is easier to push them together
Describe the movement of the particles of helium gas inside a balloon
Range of speeds
Moving in different directions
Random movement
Explain, in terms of particles, how evaporation causes the cooling of water
The fastest particles have enough energy to escape from the surface of the water
Therefore the mean energy of the remaining particles decreases
The lower the mean energy of particles, the lower the temperature
