chemical analysis

• formulations are mixtures of chemicals that are designed to create useful products
• in a formulation, each component helps to decide what the mixture's overall properties are
• to ensure that a formulation does what it is supposed to, each chemical component must be present in a precisely measured quantity
• formulations are everywhere, examples include cleaning agents, fuels, metal alloys, fertilisers and medicines
• chromatography is a process that separates a mixture into its different components
• the first phase of chromatography is when substances are picked up and carried by a mobile phase (liquid or gas)
• the second phase of chromatography is when the mobile phase moves through a stationary phase (solid or viscous liquid)
• depending on the distribution of a substance across the 2 phases, a substance moves far if it's more attracted to the mobile phase, but doesn't move far if it's more attracted to the stationary phase
• in chromatography, different compounds can sometimes be equally attracted to a solvent, therefore the number of spots a mixture produces can vary depending on the solvent used
• in paper chromatography, mixtures of soluble substances are separated
• in paper chromatography, a solvent is run through the mixture on paper, and the substances will then move up the paper at different rates, with the most soluble substance moving furthest up the paper
• the first step of the paper chromatography process is to dip the bottom of the chromatography paper into the solvent
• the second step of the paper chromatography process is that the solvent travels up the chromatography paper, and as the solvent moves, it picks up the substances being tested and carries them up the chromatography paper
• the third step of the paper chromatography process is that the components that travel furthest are highly soluble in the solvent, and are also minimally attracted to the chromatography paper
• paper chromatography practical: step 1 - use a pencil to draw a horizontal line near the bottom of the chromatography paper
• paper chromatography practical: step 2 - on this 'start line', put samples of known food colourings (A-D) alongside an unknown substance (X)
• paper chromatography practical: step 3 - place the paper in a beaker containing a small volume of solvent
• paper chromatography practical: step 4 - wait for the solvent to travel near the top of the paper
• paper chromatography practical: step 5 - by comparing spots produced by X with those produced by A-D, it should be possible to identify the unknown substance
• the test for hydrogen is the squeaky pop tes
• in the squeaky pop test, hold a lit splint at the open end of a test tube containing a gas. if the gas is hydrogen, a 'squeaky pop' sound will be produced, because hydrogen burns rapidly in the presence of oxygen to give H^2O
• the test for oxygen is the glowing splint test
• in the glowing splint test, insert a glowing splint into a test tube containing a gas. if the gas is oxygen, the splint will relight
• the test for carbon dioxide is the limewater test
• in the limewater test, bubble through, or shake carbon dioxide with, an aqueous solution of calcium hydroxide (limewater). the solution will turn from clear to cloudy
• the test for chlorine is the damp litmus paper test
• in the damp litmus paper test, insert damp litmus paper into a test tube containing a gas. if the gas is chlorine, the litmus paper will bleach and turn white