Chemistry in Society: Researching Chemistry

Question 1

What is distillation used for?

Answer 1

Distillation is used to separate a liquid from other substances

Question 2

What is the distillation process?

Answer 2

The mixture is heated in the distillation flask until the boiling point of the lowest boiling liquid is reached. The vapour is then cooled as it passes through the condenser where it turns back into a liquid, which can be collected.

Question 3

What is filtration used for?

Answer 3

Filtration can be used to separate a solid from a liquid.

Question 4

What is the filtration process?

Answer 4

Solid is separated from a liquid using filter paper. The filter paper gathers the solid and the liquid flows through the filter funnel into the flask. Care must be taken not to overfill the filter funnel as this can lead to the mixture not going through the filter paper, resulting in the mixture going into the flask unfiltered.

Question 5

What is the measuring mass by difference method?

Answer 5

Measuring mass by difference is a common method used in laboratories and often involves the use of a weighing bottle or weighing boat. An important part of the technique is to ensure chemicals are not added to the weighing vessel while on the balance, as any spillage will contaminate the balance or could affect the accuracy of the mass.

Question 6

What are the two methods for collecting a gas?

Answer 6

Over water or using a gas syringe

Question 7

What is collecting a gas over water used for?

Answer 7

Collecting a gas by bubbling through water is only appropriate if the gas is insoluble in water and can only be used to measure the volume if the collecting vessel is graduated, such as an upturned measuring cylinder. A disadvantage of collecting a gas over water is that the gas will be wet when collected.

Question 8

What is collecting a gas using a gas syringe used for?

Answer 8

The gas syringe can be used for collecting both soluble and insoluble gases and has the advantage that it can measure the volume of gas produced. Another advantage of using the gas syringe is that the gas collected will be dry.

Question 9

What is a standard flask used for?

Answer 9

Making up a standard solution.

Question 10

What is a standard solution?

Answer 10

A solution of known concentration.

Question 11

How is a standard flask used to make up a standard solution?

Answer 11

This is done by dissolving a known mass of solute in water and transferring to the standard flask with rinsings. Finally, the standard flask is made up to the mark with water.

Question 12

What is used in measuring for general lab work?

Answer 12

The markings on a beaker are very rough but helpful for general lab work. For general lab work, e.g. adding in approximate quantities of an excess acid to react with a metal, a measuring cylinder provides reasonable accuracy.

Question 13

What is used in measuring for analytical work?

Answer 13

For analytical work, i.e. experiments carried out to determine the exact quantity or concentration of a chemical, pipettes and burettes provide much greater accuracy.

Question 14

What is a pipette used for?

Answer 14

Measuring fixed volumes of liquid.

Question 15

What can a burette be used for?

Answer 15

Measuring non-standard volumes of liquid.

Question 16

What are the different methods of heating?

Answer 16

Bunsen burner, electric heating mantle and water bath

Question 17

What are the advantages and disadvantages of using a bunsen burner for heating?

Answer 17

Bunsen burners can provide rapid heating and are great for bringing solutions to boil.
However, the open flame is a fire hazard (they cannot be used safely to heat flammable liquids such as alcohols) and they heat too rapidly.

Question 18

Why is an electric heating mantle used?

Answer 18

It provides more accurate control and anything being heated can be heated to high temperatures. It can also be used for flammable liquids.

Question 19

What are the advantages and disadvantages of a water bath?

Answer 19

Water baths can be used for flammable liquids.

However, water baths cannot provide heat beyond 100 degrees Celsius.

Question 20

An experiment would be classed as being reproducible if the data obtained is what?

Answer 20

Is the same within experimental error, when repeated. It does not have to be the ‘correct’ answer.

Question 21

What are uncertainty measurements?

Answer 21

They are often reported allowing you to assess the accuracy of data or the accuracy of equipment. The lower the uncertainty measurement, the more accurate the data/equipment.