All substances are made of atoms
An atom is the smallest part of an element that can exist
An element is a substance that only contains one sort of atom
There are about 100 different elements
Most substances are compounds
A compound contains two or more elements, which are chemically combined in fixed proportions
Mixtures consist of two or more elements or compounds, which are not chemically combined
The components of a mixture retain their own properties
Mixtures can be separated by physical processes- these processes do not involve chemical reactions
Filtration is used to separate soluble solids from insoluble solids
Crystallisation is used to obtain a soluble solid from a solution
Simple distillation is used to obtain a solvent from a solution
Fractional distillation is used to separate mixtures in which the components have different boiling points
Chromatography is used to separate the different soluble, coloured components of a mixture
Slide 3
Required Practical-Analysis and purification of water samples from different sources
Sample Method
use a pH probe or suitable indicator to analyse the pH of the sample
set up the equipment as shown
heat up a set volume to 100 (degrees celcius) so that the water changes from liquid to gas
the water collects in the condenser and changes state from gas to liquid, collect this pure water in a beaker
when all the water from the sample has evaporated, measure the mass of solid that remains to find the amount of dissolved solids present in the sample
Hazards and Risks
there is a risk of the experimenter burning themselves on hot equipment, so care must be taken during and after the heating process
Atom- the smallest quantity of an element that can take part in a chemical reaction, consisting of a positively charged nucleus made up of protons and neutrons, surrounded by negatively charged electrons
Element- a substance made of only one type of atom
Compound- a substance containing atoms of two or more elements, which are chemically combined, in fixed proportions
Equation- a scientific statement that uses chemical names or symbols to sum up what happens in a chemical reaction
Reactants- the substances that react together in a chemical reaction
Products- the substances produced in a chemical reaction
Mixture- a combination of two or more elements or compounds, which are not chemically combined together
Filtration- separation techniques used to separate insoluble solids from soluble solids
Crystallisation- technique used to obtain a soluble solid from a solution
Simple Distillation- technique used to separate a substance from a mixture due to a difference in the boiling points of the components in the mixture
Fractional Distillation- a separation technique used to separate mixtures which contain components with similar boiling points
Chromatography- a separation technique used to separate the coloured components of mixtures