1.1 States of Matter

REVISION NOTES

IGCSE Edexcel Chemistry

1.1.1 Understand the three states of matter in terms of the arrangement, movement and energy of the particles

1.1.2 Understand the interconversions between the three states of matter in terms of:

The names of the interconversions
How they are achieved
The changes in arrangement, movement and energy of the particles.

Interconversion between different states of matter is a physical change

There is no new substance formed after the change
Although the forces between the particles change, the particles themselves and their chemical properties are still the same

From solid to liquid to gas (left to right):

Particles gain more kinetic energy through heating
Move around more and become more randomly arranged
Particles are further apart

From gas to liquid to solid (right to left):

Particles lose kinetic energy (therefore release heat)
Move less and become more regularly arranged
Particles are closer together

When there is a change in state, the temperature does not change

The heat supplied is used to break the attraction forces between particles, instead of raising the temperature

1.1.3 Understand how the results of experiments involving the dilution of coloured solutions and diffusion of gases can be explained

DIFFUSION

Diffusion: random movement of particles from an area of high concentration to an area of low concentration
Diffusion only happens in liquid and gas
- Because particles need to be able to move around

Both diffusion and dilution support the theory that:

All matter is made up of tiny, moving particles

Experiment 1: Diffusion in Gas

Observation

Bromine gas is placed at the bottom of the container
After several minutes, bromine gas diffuses to the top of the container
Bromine gas is evenly distributed in the container

Explanation

Air particles and bromine gas particles are moving randomly in the container
Bromine gas particles travel from an area of high concentration to low concentration

Experiment 2: Diffusion in Liquid

Observation

Potassium manganate (VII) crystals are placed in water
Potassium manganate molecules diffuse through the solution
An even purple solution is formed in the end

Explanation

Water molecules and potassium manganate (VII) crystals are moving randomly
Particles are mixed together, travelling from an area of high concentration to low concentration
However, diffusion in liquid is slower than diffusion in gas because the particles move more slowly and are more closely packed together

Experiment 3: Dilution

Dilution, together with diffusion, is one of the experiments which support the theory that: all matter is made up of tiny, moving particles.

Observation

After potassium manganate (VII) crystals are dissolved in water, it becomes a solution
The solution can then be diluted several times
The colour fades but does not disappear

Explanation

There are many potassium manganate (VII) particles present in the solution
When the solution is diluted, more water is added
However, the number of potassium manganate particles does not change
The colour of the solution fades because particles are evenly distributed in solution with larger and larger volume

1.1.4 Know what is meant by the terms:

Solvent
Solute
Solution
Saturated solution

1.1.5C Know what is meant by the term solubility in the units g per 100 g of solvent

SOLUBIILITY

Definition: the amount of solute that will dissolved in a given volume of solvent
It can be expressed in g per 100g of solvent
Different substances have different solubilities

Solubility of solids depend on temperature:

When temperature increases, the solubility of solids increases

Solubility of gases depend on both temperature and pressure:

When temperature increases, the solubility of gases decreases
When pressure increases, the solubility of gases increases

1.1.6C Understand how to plot and interpret solubility curves

x-axis: Temperature (in ^oC or Kelvin)

y-axis: Solubility (in g per 100g of water)

To plot a solubility curve:

The saturation point at different temperatures should be determined first
Saturation point is the maximum mass of solvent that can dissolve in 100g of water

Always remember:

The readings on solubility curve are per 100g water, while the question might ask more than/multiples of 100g water
When temperature increases:
- Solids become more soluble
- Gases become less soluble

1.1.7C Practical: investigate the solubility of a solid in water at a specific temperature

AIM

To measure the solubility of a salt at different temperatures

EQUIPMENT LIST

250 cm³ beaker
Thermometer
Water bath
Glass rod
Digital mass balance

CHEMICALS REQUIRED

Deionised water
A powdered solid (e.g.sodium chloride)

METHOD

Set the water bath to the desired temperature.
Pour 200 cm³ of deionised water into a 250 cm³ beaker.
Place the beaker into the water bath. Keep the thermometer in the beaker to ensure the temperature stays constant throughout the experiment.
Wait for the temperature of water to stabilise at the desired temperature.
Add known masses of sodium chloride (NaCl) bit by bit until it stops dissolving and remains solid in the solution.
Record the mass of solid that was soluble.
Repeat steps 1-6 with the water at different temperatures.

KEY POINTS

If the solid is very soluble, the solubility could be investigated by timing how long it takes a known mass of solid to dissolve at each temperature.
A larger mass of solid should dissolve at higher temperatures
To compare the solubility of different solids, keep the temperature of the water the same in each trial but use different solids.

SAFETY PRECAUTIONS

Avoid touching hot parts of the water bath and handle the beaker with care when it is hot.
Be careful with the glassware and clear up any broken glass immediately.
All chemicals must not be ingested.

Result Table

RESULT GRAPH

Calculate the solubility of NaCl at each temperature
- Solubility = mass of NaCl dissolved in water ÷ mass of water x 100
Plot a graph
- x-axis: temperature (in ^oC or Kelvin)
- y-axis: solubility (in g per 100g of water)