CHEMISTRY REVISION WORKSHEET
Equipments:
states of matter
Solid:
- Particles are arranged regularly and packed closely together
- Particles are only able to vibrate and can’t move around
- Particles have strong forces of attraction between them, which keep them together
- Very dense
Liquid:
- Particles are mostly touching, but some gaps have appeared.
- Less dense than solids
- The forces between the particles are less effective
- The particles can move around each other
Gas:
- Particles are moving randomly at high speed in all directions
- The particles are much further apart
- Can be squashes or compressed
- There are almost no forces of attraction between them
Why is hydrogen a gas? It has very weak attractive forces between its atoms (hydrogen exists as a
molecule because it’s diatomic) because it is very small.
,The particles in a liquid have more kinetic energy than the particles in the solid so energy has to be
supplied to convert a solid to a liquid.
A small number of substances can change directly from a solid to a gas, or from a gas to a solid.
Boiling and evaporation.
Boiling: Evaporation:
- Occurs when a liquid is heated so - In any liquid or gas, the average
strongly that the particles are moving speed of the particles varies with the
fast enough to overcome all the forces temperature.
of attraction between them. The - At each temperature, some particles
stronger the forces of attraction will be moving faster than the average
between particles, the higher the and others more slowly.
boiling point of the liquid. This is - Some very fast particles at the surface
because more energy is needed to of the liquid will have enough energy
overcome these forces of attraction. to overcome the forces of attraction
- Bubbling between the particles - they will break
- Only happens at boiling point away to form a gas.
- Happens throughout the liquid - No bubbling
- Happens at all temperatures
- Only happens only at the surface of
the liquid because the fastest-moving
molecules are at the top, and they
escape while the slow ones are left
behind
Diffusion:
- Diffusion is the spreading out of particles from an area with high concentration to an area with
lower concentration
E.g:
- Ammonia and hydrochloric acid evaporate and start moving towards each other (to low
concentration in the middle). A product (NH4Cl) was formed as a solid ring.
- The ring is not in the middle as ammonia was moving faster because it had higher velocity as
its molecules had smaller mass,
- Diffusion includes colour spreading in the water.
,Solubility: mass of solute that can dissolve in 100g solvent, at a specific temperature
Soluble: a substance which can dissolve in a specific solvent forming a solution
Solute - dissolves, solvent - gets dissolved in
Saturated solution: one in which the maximum amount of solute has been dissolved
100 g of water = 100 cm3
Because mass and volume are related to density
The density of water is 1, so 1 cm3 of water has a mass of 1 gram
Practical: Investigating the solubility of a solid in water.
Measuring the solubility of potassium nitrate in water at 40°C:
1. Weigh an evaporating basin.
2. Heat a boiling tube of water to just above 40°C
3. Add potassium nitrate to the water in the boiling
tube and stir rapidly until no more of it will dissolve and there
is undissolved solid left over.
4. Allow the solution to cool to exactly 40°C
5. Pour off some of the solution into the evaporating
basin (it is important that you only pour off solution and
no solid). You do not have to pour off all the solution.
6. Weigh the evaporating basin and contents.
7. Heat the evaporating basin and contents gently to
evaporate off all the water.
8. When it looks as if all the water has evaporated, weigh the evaporating basin and contents.
9. Heat the evaporating basin and contents again and then re-weigh. This is to make sure that
all the water has, indeed, evaporated and is called heating to constant mass.
Calculating the mass of the solid and the mass of water evaporated from the solution:
Mass of crystals = (mass of evaporating basin + dry crystals) - mass of evaporating basin
Mass of water = (mass of evaporating basin + solution) - (mass of evaporating basin + dry crystals)
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒
Solubility (g/100g) =
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑠𝑜𝑙𝑣𝑒𝑛𝑡
× 100
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 (𝑔)
Maximum mass that would dissolve = 100 𝑥 𝑠𝑜𝑙𝑢𝑏𝑖𝑙𝑖𝑡𝑦 (𝑔/100𝑔)
, elements, compounds and mixtures
Element - made of one type of atom
Compound - two or more types of atom chemically bonded with a fixed ratio
Molecule - two or more atoms bonded element or compound
Mixtures - two or more atoms or molecules not chemically bonded
What is the difference between a pure substance and a mixture?
Pure substances:
Melting and boiling point is an exact temperature
Mixtures:
Melting and boiling point is a range of temperatures
Filtration - separate a solid from a liquid
• The substance left in the filter paper is called the residue
The liquid that comes through is called the filtrate.
Crystallisation - separate a solute from a solution
• The solution is heated to boil off some of the water until an
almost saturated solution is formed.
Simple distillation - separate the components of solution
• First, apply heat for the solution to boil, it boils and then
condenses back into liquid.
Fractional distillation - separate a mixture of liquid with different
boiling points
• The substance with lower temperature stays vapour and travels
into the condenser and back into liquid. The substance with higher
boiling point condenses in the column and travels back into the
flask
Paper chromatography - separate a variety of mixtures
- use a pencil to draw the base line so it does not dissolve like a pen and
the ink moves up the chromatography paper
- make sure the solvent does not go above - the pencil line so the
inks/colouring does not dissolve in the solvent
- put a lid so the atmosphere becomes saturated with the solvent. stop
evaporation of solvent from the paper
- either use water or ethanol for the solvent
- the highest level of solvent on the paper is called the solvent front
Equipments:
states of matter
Solid:
- Particles are arranged regularly and packed closely together
- Particles are only able to vibrate and can’t move around
- Particles have strong forces of attraction between them, which keep them together
- Very dense
Liquid:
- Particles are mostly touching, but some gaps have appeared.
- Less dense than solids
- The forces between the particles are less effective
- The particles can move around each other
Gas:
- Particles are moving randomly at high speed in all directions
- The particles are much further apart
- Can be squashes or compressed
- There are almost no forces of attraction between them
Why is hydrogen a gas? It has very weak attractive forces between its atoms (hydrogen exists as a
molecule because it’s diatomic) because it is very small.
,The particles in a liquid have more kinetic energy than the particles in the solid so energy has to be
supplied to convert a solid to a liquid.
A small number of substances can change directly from a solid to a gas, or from a gas to a solid.
Boiling and evaporation.
Boiling: Evaporation:
- Occurs when a liquid is heated so - In any liquid or gas, the average
strongly that the particles are moving speed of the particles varies with the
fast enough to overcome all the forces temperature.
of attraction between them. The - At each temperature, some particles
stronger the forces of attraction will be moving faster than the average
between particles, the higher the and others more slowly.
boiling point of the liquid. This is - Some very fast particles at the surface
because more energy is needed to of the liquid will have enough energy
overcome these forces of attraction. to overcome the forces of attraction
- Bubbling between the particles - they will break
- Only happens at boiling point away to form a gas.
- Happens throughout the liquid - No bubbling
- Happens at all temperatures
- Only happens only at the surface of
the liquid because the fastest-moving
molecules are at the top, and they
escape while the slow ones are left
behind
Diffusion:
- Diffusion is the spreading out of particles from an area with high concentration to an area with
lower concentration
E.g:
- Ammonia and hydrochloric acid evaporate and start moving towards each other (to low
concentration in the middle). A product (NH4Cl) was formed as a solid ring.
- The ring is not in the middle as ammonia was moving faster because it had higher velocity as
its molecules had smaller mass,
- Diffusion includes colour spreading in the water.
,Solubility: mass of solute that can dissolve in 100g solvent, at a specific temperature
Soluble: a substance which can dissolve in a specific solvent forming a solution
Solute - dissolves, solvent - gets dissolved in
Saturated solution: one in which the maximum amount of solute has been dissolved
100 g of water = 100 cm3
Because mass and volume are related to density
The density of water is 1, so 1 cm3 of water has a mass of 1 gram
Practical: Investigating the solubility of a solid in water.
Measuring the solubility of potassium nitrate in water at 40°C:
1. Weigh an evaporating basin.
2. Heat a boiling tube of water to just above 40°C
3. Add potassium nitrate to the water in the boiling
tube and stir rapidly until no more of it will dissolve and there
is undissolved solid left over.
4. Allow the solution to cool to exactly 40°C
5. Pour off some of the solution into the evaporating
basin (it is important that you only pour off solution and
no solid). You do not have to pour off all the solution.
6. Weigh the evaporating basin and contents.
7. Heat the evaporating basin and contents gently to
evaporate off all the water.
8. When it looks as if all the water has evaporated, weigh the evaporating basin and contents.
9. Heat the evaporating basin and contents again and then re-weigh. This is to make sure that
all the water has, indeed, evaporated and is called heating to constant mass.
Calculating the mass of the solid and the mass of water evaporated from the solution:
Mass of crystals = (mass of evaporating basin + dry crystals) - mass of evaporating basin
Mass of water = (mass of evaporating basin + solution) - (mass of evaporating basin + dry crystals)
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒
Solubility (g/100g) =
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑠𝑜𝑙𝑣𝑒𝑛𝑡
× 100
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 (𝑔)
Maximum mass that would dissolve = 100 𝑥 𝑠𝑜𝑙𝑢𝑏𝑖𝑙𝑖𝑡𝑦 (𝑔/100𝑔)
, elements, compounds and mixtures
Element - made of one type of atom
Compound - two or more types of atom chemically bonded with a fixed ratio
Molecule - two or more atoms bonded element or compound
Mixtures - two or more atoms or molecules not chemically bonded
What is the difference between a pure substance and a mixture?
Pure substances:
Melting and boiling point is an exact temperature
Mixtures:
Melting and boiling point is a range of temperatures
Filtration - separate a solid from a liquid
• The substance left in the filter paper is called the residue
The liquid that comes through is called the filtrate.
Crystallisation - separate a solute from a solution
• The solution is heated to boil off some of the water until an
almost saturated solution is formed.
Simple distillation - separate the components of solution
• First, apply heat for the solution to boil, it boils and then
condenses back into liquid.
Fractional distillation - separate a mixture of liquid with different
boiling points
• The substance with lower temperature stays vapour and travels
into the condenser and back into liquid. The substance with higher
boiling point condenses in the column and travels back into the
flask
Paper chromatography - separate a variety of mixtures
- use a pencil to draw the base line so it does not dissolve like a pen and
the ink moves up the chromatography paper
- make sure the solvent does not go above - the pencil line so the
inks/colouring does not dissolve in the solvent
- put a lid so the atmosphere becomes saturated with the solvent. stop
evaporation of solvent from the paper
- either use water or ethanol for the solvent
- the highest level of solvent on the paper is called the solvent front
