Topic 2 - States of matter and mixtures Flashcards
Describe the arrangement, movement and the relative energy of particles in a gas
In a gas particles have the most energy and are therefore spread out. They can flow because their particles can move in all directions and can be compressed because their particles are far apart and have space to move into.
Describe the arrangement, movement and the relative energy of particles in a liquid
In a liquid particles have greater energy than a solid and are able to flow because their particles can move around. However, the particles are close (fixed) so together so they can’t be easily compressed.
Describe the arrangement, movement and the relative energy of particles in a solid
A solid has low energy and particles are fixed. They cannot flow because their particles can’t move and cannot be compressed because their particles are close together.
Define physical changes and chemical changes in comparison.
Physical changes (such as state changes) involve the forces between the particles of the substances but the particles themselves don’t change. In chemical a new product is formed.
Name the main state changes between the three states
solid → liquid: melting
liquid → solid: freezing
liquid → gas: boiling/evaporating
gas → liquid: condensing
Explain melting and evaporation
Energy must be transferred, by heating, to a substance. During this, the particles gain energy which is used to break or overcome some of the bonds between particles (or all the bonds during evaporation)
Explain condensing and freezing
Energy must be transferred from a substance to the environment. During this, the particles lose energy as bonds form between the particles.
Define ‘pure’ in chemistry
A pure substance consists only of one element or one compound
Define a mixture in chemistry
Two or more different substances, which are not chemically joined together.
Therefore, the temperature changes as an impure substance changes state.
Explain simple distillation
It is used to separate a solvent from a solution. The dissolved solute must have a higher boiling point than the solvent.
The solution is heated by a Bunsen burner. The water vapour cools in the condenser and drips into a beaker as the pure solvent. The solute remains in the beaker.
Explain fractional distillation
It is used to separate different liquids from a mixture of liquids.
The different liquids must each have different boiling points.
When the mixture is heated it evaporates and vapour rises through a column which is hot at the bottom and cold at the top. The substance with the lowest boiling point is collected at the top of the column as it moves into the condenser and it comes out of this into a beaker as a pure liquid.
Explain filtration
It is used to separate an insoluble solid from a liquid.
A funnel with filter paper is placed in a beaker. The mixture is poured through the filter funnel. The liquid drips through the filter paper but the solid particles are caught in the paper.
Explain crystallisation
It is used to separate a soluble salt from the solution it was dissolved in.
An evaporating basin with the solution in it is placed on a tripod over a Bunsen burner. The liquid evaporates and solid crystals are left behind.
To obtain large, regularly-shaped crystals use a boiling water bath rather than a tripod and Bunsen burner and stop heating before all the solvent has evaporated, filter or pour away the excess liquid once it has cooled. You can dry the crystals using a warm oven.
Explain paper chromatography
It is used to separate mixtures made up of soluble substances and give information to help identify them.
Draw a baseline on the chromatography paper using a pencil. Place a spot of each sample mixture on the baseline. Our the solvent into a beaker. Place a rod over the beaker and attach the paper to it so just the paper’s base touches the solvent.
The solvent will travel up the paper taking soluble pigments from the sample mixture with it so they create different spots along the paper. Remove it before the solvent reaches the top. This is a chromatogram.
Describe paper chromatography
The separation of mixtures of soluble substances by running a solvent (mobile phase) through the mixture on the paper (the paper contains the stationary phase), which causes the substances to move at different rates over the paper
