Particle model of matter

What is density

This is the mass per unit volume of a material

What are the features of solids

• the particles are closely packed

• The particle vibrates about fixed position

• Solids have definite shape and volume

What are the features of liquids

• the particles are closely packed

• The particles can flow over one another

• They have no definite shape

• They have definite volume

What are the features of gases

• the particles are far apart

• The particles move randomly

• They have no definite shape and no fixed volume

Why are gases highly compressible

• there are large gaps between particles

• It is easier to push the particles closer together than in liquids and solids

Experiment 1: measuring the density of regularly shaped objects

Variables

• independent variable: type of shape/volume

• Dependent variable: mass of the variable object

Experiment 1: measuring the density of regularly shaped objects (Cont’d)

• place the object on the digital balance and note down its mass

• Use either a ruler , vernier calipers or micrometer to measure the objects dimensions

• Repeat these measurement and take an average of these readings before calculating the density

Experiment 2: determining the density of irregular shaped objects

• independent variable: mass

• Dependent variable: volume of displaced water

Experiment 2: determining the density of irregular shaped objects (Cont’d)

Method

• place the object on a digital balance and note down its mass

• Fill the eureka can with water up to a point just below the spout

• Place an empty measuring cylinder below the spout

• Carefully lower the object into the eureka

• Measure the volume of displaced water in the measuring cylinder

• Repeat these measurement and take an average before calculatin the density

  The volume of displaced water is equal to the volume of the object

Experiment 3: measuring the density of liquids

• independent variable: volume of water added

• Dependent variable: mass of the cylinder

Experiment 3: measuring the density of liquids (Cont’d)

Method

• Place an empty measuring cylinder on a digital balance and note down the mass

• Fill the cylinder with water and note down the volume

• Note down the new reading on the digital balance

• Repeat the measurements and take an average before calculating the density

  mass of the liquid= mass of cylinder with water - mass or cylinder

What are the systematic errors when measuring density

• ensuring the digital balance is set to zero before taking measurement of mass

What are random errors when measuring density

• Error when measuring lengths ( make sure to take repeat readings and calculate an average to keep error to a minimum)

• Place the irregular object in the eureka carefully as dropping from an height might cause water to splash which will lead to an incorrect volume reading

What are the safety precautions when measuring density

• there is a lot of glassware in these experiments make sure they are handled carefully

• Water should not be poured into the measuring cylinder when it is on the electric balance. This could lead to electric shock

• Make sure to stand up during the whole experiment to react quickly to any spills

What is internal energy

the total amount of kinetic and potential energy in the particles of an object

What happens when a substance changes it state

• the potential energy of its molecules increase allowing them to overcome the intermolecular forces of attraction

• The kinetic energy remains the same meaning that the temperature will remain the same even the substance is still being heated

What is specific heat capacity

This is the amount of energy needed to raise the temperature of 1kg of an object by 1 degree

What does it mean for an object to have low specific heat capacity

It heats up and cools down quickly. It takes less energy to change it’s temperature

What does it mean for an object to have high specific heat capacity

It heats up and cools down slowly. It takes more energy to change its temperature

How are objects with low specific capacity useful

Good electrical conductors like copper and lead are excellent conductors of heat

How are objects with high specific capacity useful

Water is ideal for heating homes as the water remains hot in a radiator for a long time

What is latent heat

The energy required for a substance to change state.

Why does the temperature of an object not change when it changes state

This is because energy is used to overcome intermolecular forces of attraction between the molecules instead of increasing the kinetic energy of the molecules and hence the temperature

What is specific latent heat

The amount of energy needed to change the state of 1kg of a substance with no change of temperature

What are the two types of specific latent heat

• specific latent heat of fusion

• Specific latent heat of vaporization

What is specific latent heat of fusion

The amount of energy needed to change 1kg of a substance from solid to liquid state whilst at constant temperature

What is specific latent heat of vaporization

The amount of energy needed to change 1kg of a substance from liquid to vapour state whilst at constant temperature

Explain the process of heating

• When energy is transferred to a solid, the temperature starts to increase as the particles gain kinetic energy and vibrate faster 

• When the temperature of the substance reaches its melting point, the energy transferred to the substance is now used to overcome the intermolecular forces of attraction holding the particles in their solid structure

• The temperature of the substance stops increasing 

Explain the process of cooling

• When energy is transferred away from a gas, the temperature starts to decrease as the particles lose kinetic energy and move slower 

• When the temperature of the substance reaches its boiling point, the energy transferred away from the substance is now taken from the energy used to overcome the intermolecular forces of attraction

• The temperature of the substance stops decreasing

• The particles now succumb to those intermolecular forces of attraction and are held together in their liquid structure 

What are the differences of SHC and SLH

• SHC has a symbol of C while SLH has a symbol of L

• SHC has a unit of j/kg per degree while SLH has a unit of j/kg

• SHC is involved in changing temperature while SLH is involved in changing stage

• SHC is the same for the same material at all temperatures while SLH is different for the same material depending on the change of state

What is brownian motion

This is the random motion of tiny particles in a fluid

What happens when a gas is at high pressure

There are more frequent collisions on the container walls and therefore more force per unit area

What happens when a gas is heated up

There are more collisions with the walls of the container which creates an increase in pressure

What is the relationship between temperature and pressure

At constant volume an increase in temperature increases the pressure of a gas

What happens when a gas is compressed

Decreases the volume which increases the pressure

What happens when a gas is expanded

The volume is increased which decreases the pressure

What is work

This is the transfer of energy by force

What happens when work is done on a gas

Increase in internal energy and can also cause increase in temperature

What happens when a gas is compressed

• force is used to push a piston by a certain distance

• This decreases the volume

• The molecules move around faster and therefore have more KE

• increase in KE leads to increase in temperature