Chapter 2

Question 1

Name appropriate apparatus for the measurement of time, temperature, mass and volume

Answer 1

time - timer
temperature - thermometer / temperature probe
mass - digital mass balance
volume - burettes, pipettes and measuring cylinders

Question 2

What is the importance of purity in substances in everyday life, e.g. foodstuffs and drugs?

Answer 2

Impurity of drugs can lead to dangerous side effects and impurity of food may cause health problems when it is ingested. If it was not pure it could not really be trusted.

Question 3

How does paper chromatography work?

Answer 3

Different substances have different solubilises and molecular mass. There for they would either travel further so shorter depending on its solubility and mass. This separates them.

Question 4

Rf Value

Answer 4

the distance travelled by the solute/ the distance travelled by the solvent

Question 5

Identify substances and assess their purity from

melting point and boiling point information

Answer 5

A pure substance has an exact melting and boiling point, however impure substances would have a ranging or different boiling and melting point.

Question 6

Outline the process of chromatography

Answer 6

1. draw a pencil line 2cm from the bottom of the chromatography paper
2. place your compound dots at the line and label each dot.
3. place it in distilled water in a beaker
4. remove the paper and mark where the solvent ended
5. Dry the paper

Question 7

Describe and explain methods of purification by the use of filtration

Answer 7

If the substance is insoluble, it can go through filtration.

1. put a piece of filter paper into the funnel and place the two over a beaker.
2. Pour the mixture in the funnel so the liquid it collected but the substance stays in the funnel
3. pour deionised water over the substance in the funnel to remove any extra solvent
4. leave the substance to dry.

Question 8

Describe and explain methods of purification by the use of crystallisation

Answer 8

If the substance is soluble, it can go through crystallisation.

1. place the solution into the evaporating basin
2. Warm the solution slightly to evaporate the solvent
3. Remove from heat and allow the mixture to cool before all the solvent evaporates.
4. Leave to evaporate without heating. Dry and remove the crystals

Question 9

Describe and explain methods of purification by the use of distillation

Answer 9

If the substance is a liquid compound, it can go through distillation.

1. you add the liquid to a beaker; and heat it using a Bunsen burner
2. Using knowledge of their fixed points and boiling points, the one with the lower boiling point will evaporate first.
3. the beaker is connected to the condenser which allows the evaporated gas to condense and be removed as a liquid.