Separation Techniques and Basic Chemistry

Question 1

Elements are pure substances made up of only one type of atom

Question 2

Compounds are two or more types of atoms (elements) chemically bonded together

Question 3

Mixtures are two or more compounds or elements mixed together but not chemically bonded

Question 4

Formulations are mixtures designed and created for a purpose, e.g. Fuels, paints, medicines, foods, fertilisers

Question 5

Mixtures can be separated by physical processes such as filtration, crystallisation, simple distillation, fractional distillation, and chromatography

Question 6

Filtration separates an insoluble solid from a soluble solid in solution or a liquid. It involves filter paper and a filter funnel to catch small solid particulates but allow the liquid through

Question 7

Crystallisation can be used to delegate a soluble solid from its solution. It involves heating the solution so the the solvent evaporates, leaving behind solid crystals

Question 8

Simple distillation can separate a soluble solid from its solution, keeping both the solute and the solvent. It is similar to crystallisation, but involves an Leiblig condenser, which captures and condenses the evaporated gas to be collected as a liquid

Question 9

Fractional distillation can separate two or more miscible liquids, by using a fractionating column to give the pure solute

Question 10

Chromatography can be used to separate mixtures and is used to identify substances. It uses a solvent distributing separate parts of the mixture different distances up the paper, depending on the attraction between the solvent and compound.

Question 11

Ratio of the distance moved by a compound to the distance moved by the solvent can be expressed as its Rf value.
Rf = substances distance/solvent distance. Different compound have different Rf values in different solvents, which can be used to identify compounds. Pure compounds or elements will produce a single spot in all solvents

Question 12

The test for hydrogen uses a burning splint at the end of the test tube. A squeaky pop is heard if hydrogen is present.

Question 13

The test for oxygen uses a glowing splint inserted into the test tube. The splint relights in oxygen

Question 14

The test for Carbon Dioxide use limewater. When Carbon Dioxide is bubbled through limewater, it turns cloudy

Question 15

The test for chlorine uses litmus paper. When damp litmus paper is put into chlorine gas it is bleached and turns white.

Question 16

Water that is safe to drink is known as potable water, however it is not pure in a chemical sense as it contains dissolved substance

Question 17

To obtain potable water :
1. Water is passed through a screen to catch large objects like leaves
2. A settlement tank is used so soil and sand settle out
3. Aluminium sulphate and lime are are added, causing dirt to clump and sink
4. The water is passed through fine gravel and sand as the final filter layer
5. A small amount of chlorine is added to kill harmful bacteria, and the Ph is confirmed to be 7

Question 18

Sewage treatment involves
1. Screening to remove large matter
2. Primary sedimentation, to produce sewage sludge and effluent
3. Anaerobic digestion of sewage sludge
Aerobic biological treatment of effluent.

Question 19

The three states of matter are solid liquid and gas. The amount of energy needed to change state depends on the inter molecular forces and the type of bonding

Question 20

In chemical equations, the three states of matter are shown as (s), (l) and (g), with (aq) for aqueous solutions

Question 21

Paper chromatography required practical - see 3rd form notes

Question 22

Required practical 8 analysis and purification of water samples, ask Mr D.