Welcome to this course on chemical analysis. In the following modules, we will look at pure substances, formulations, chromatography and the identification of common gases. This course covers Topic 5.8 Chemical Analysis which is examined on Chemistry Paper 2 of the GCSE AQA Combined Science Course.
In nature, elements are often blended together to greater or lesser degrees. Compounds are substances that are chemically bonded together. Mixtures are elements/compounds that are mixed together, though not at the chemical level.
Formulation chemistry is the mixing of compounds/substances that do not react with each other but produce a mixture with the desired characteristics/properties to suit a particular application/use.
A formulation is a mixture that has been designed as a useful product.
Many products are complex mixtures in which each chemical has a particular purpose.
Formulations are made by mixing the components in carefully measured quantities to ensure that the product has the required properties.
Examples: Fuels, cleaning agents, paints, medicines, alloys, fertilisers and foods.
Chromatography is a technique used by chemists. It can be used to identify and separate substances that are contained in a mixed solution. There are several different types including paper and thin layer chromatography.
This illustration demonstrates paper chromatography in action. This experiment can be performed in a laboratory using a simple solvent such as water. The paper is submerged and the resultant spots show the chemical composition.
Identification of Common Gases
The test for hydrogen uses a burning splint held at the open end of a test tube of the gas. Hydrogen burns rapidly with a pop sound.
The test for oxygen uses a glowing splint inserted into a test tube of the gas. The splint relights in oxygen.
The test for carbon dioxide uses an aqueous solution of calcium hydroxide (lime water). When carbon dioxide is shaken with or bubbled through limewater the limewater turns milky (cloudy).
The test for chlorine uses litmus paper. When damp litmus paper is put into chlorine gas the litmus paper is bleached and turns white.