In this topic you will look at laboratory tests that analysts have developed to detect specific chemicals. The tests are based on reactions that produce a gas with distinctive properties, or a colour change or an insoluble solid that appears as a precipitate. 

Instrumental methods provide fast, sensitive and accurate means of analysing chemicals, and are particularly useful when the amount of chemical being analysed is small. Forensic scientists and drug control scientists rely on such instrumental methods in their work.

Specification links:

• Set 1 - 4.1.2.1 - 4.1.3.2

• Set 2 - 5.1.2.1 - 5.1.2.6

• Set 3 - 5.1.2.1 - 5.1.2.6

Task 1b:  Listen to the podcast for an overview of this topic:

Task 2b: Make notes that:

• Define pure and impure substances.

• Define formulations.

• Describe the difference between pure substances, impure substances, and formulations.

• Explain how melting point and boiling point data can be used to determine the purity of a substance.

• Explain uses of formulations.

• Complete the questions on slide 21.

Task 3b: Make notes that:

• Plan and carry out a method for paper chromatography. 

• Describe a use of chromatography.

• Explain how chromatography separates solutes.

• Calculate Rf values from given data.

• Explain why different substances and different conditions will have different Rf values.

Task 4b: Make notes that:

• Describe how to carry out the laboratory test for hydrogen.

• Describe how to carry out the laboratory test for oxygen.

• Describe how to carry out the laboratory test for  carbon dioxide.

• Describe how to safely carry out the laboratory test for chlorine gas. 

Task 8d: Make a mind map or other revision resources and add them to your revision folder

Task 9:  Complete the end of unit quiz to make sure you have understood this topic