P6-Density Flashcards
How do you calculate the density of a regular object
- Calibrate your scales and measure the mass of the object
- Calibrate your calliper and measure the length and width of the object . Multiply these values to get a volume for the object
- Use your equation to work out the density of the object from these values
How do you calculate the density of an irregular object
- Calibrate the scales and measure the mass of the object
- Fill the eureka can to the top with water. Then let the excess water drip out until the water settles just under the hole.
- Place the measuring cylinder under the nosel. Then place your object into the eureka can. Make sure no water splashes and maybe place your object in with string so your fingers dont displace any water
- Measure the volume of displaced water that has gone into the measuring cylinder. Making sure to measure from the bottom of the meniscus
- Use the equation density = mass divided by volume to work out the density
How do you measure the mass of a liquid
- Place a measuring cylinder on the scales and zero the scales
- Place 10 cm3 of the liquid into the measuring cylinder and record the mass of the liquid
- Place another 10 cm3 of liquid into the measuring cylinder and measure the mass of the liquid again
- Use the mass and volume to calculate a density for each of the measurements and find out an average density for the liquid
What is the equation for density
Density = mass divided by volume
Describe the features of particles in a solid
- Strong forces pf attraction hold the particles in a solid in a fixed regular arrangement
- The particles have little energy and just vibrate round their fixed positions
- The density of a solid is highest because the particles are closest together
Describe the features of particles in a liquid
- There are weaker forces of attraction between particles so the particles are able to move past each other and form irregular arrangements. They are still close together though
- The particles have more energy than the particles in solids so they are able to move in random directions at high speeds
- Liquids are less dense than solids
Describe the features of particles in a gas
- There are almost no forces of attraction between the particles in a gas
- The particles have more energy than particles in liquids and solids. They are free to move in random directions at high speeds
- Gases have the lowest densities as the particles are the least close together
What is the internal energy store of a substance
The internal energy store of a substance is the total energy that the particles have in their kinetic and potential energy stores
The energy in the particle’s potential energy store is due to the positions of the particles
The energy in the particle’s kinetic energy store is due to the motion( vibration and movement )of individual particles
How does heating affect a particles internal energy store
Heating transfers energy to the particles in the substance. This energy goes into the kinetic energy store of the particles and the particles move faster.This increases the internal energy of the substance
When will a change in state happen
A change in state will happen if particles have been heated enough. The particles will have enough energy in their kinetic energy store to break the intermolecular forces of attraction that are holding them together .
How does mass of a substance change when a change of state occurs
The mass of a substance does not change.
- This is because when a change if state occurs the number of particles doesnt change they are just arranged differently.
- This means mass is conserved
What happens if you reverse a change in state
If you reverse a change in state the particles return to their original form and go back to their original properties
What happens to the temperature of a substance when it is melting or boiling
When a substance is actually melting or boiling , energy is being put into the substance so the internal energy of the substance is increasing. But the energy is being used to break the intermolecular forces of attraction rather than to increase the temperature of the substance
This means that the temperature does not change
What happens to the temperature of a substance when it is freezing or condensing
When a substance is freezing or condensing, energy is being released because bonds are being made. This decreases the internal energy of the substance but does not decrease the temperature as the energy is being used to make the bonds rather than to change the temperature
What is latent heat
Latent heat is the amount of energy needed to change the state of a substance
What is specific latent heat of fusion and what is the equation for it
Specific latent heat of fusion refers to the energy needed to change a 1kg substance from a solid state to a liquid state
Specific latent heat of fusion= energy (j) divided by mass (kg)
What is specific latent heat of vaporisation
Specific latent heat of vaporisation refers to the energy needed to change 1kg of a substance from a liquid to a gas
Specific latent heat of vaporisation = energy(j) divided by mass (kg)
How does pressure exerted by a gas increase as temperature increases
When a substance is heated its particles gain kinetic energy and move faster. The molecules therefore collide with surfaces more frequently and with more force .
Therefore pressure increases as temperature increases
What is the equation for pressure
Pressure(N/m2) = force(N) divided by area (m2)
What is pressure
Pressure is the continuous colliding of particles with a surfaces
More particles= higher pressure
Less particles=lower pressure
What equation links pressure and volume
Pressure x volume = constant
P1xV1=P2xV2
What is Boyles law
Boyles law states that for a fixed amount of gas at a fixed temperature , pressure is inversely proportional to volume.
As pressure increases volume decreases and vica versa
Why does pressure increase as volume decreases
Due to having a smaller volume the particles collide more frequently with the internal surface. Thsi increases the force per unit area therefore increasing the pressure
What would happen to pressure if the volume of the container increased
Pressure would decrease if the volume of the container increased .
- This would be because there would be more space between the particles and the internal surface and overall less frequent collisions with the internal surface.
- This would ultimately mean that there would be less force over a larger area so less pressure
How does doing work on a gas increase temperature
If you transfer energy by applying a force then you do work on a gas.
Doing work on a gas transfers energy to its internal energy store .
This increases the energy in the kinetic energy stores of the particles within the gas
By increasing the energy in the kinetic energy store you increase the temperature of the gas (temperature is average kinetic energy)
So overall doing work on a gas increases temperature
