Chemical analysis

• Pure substances contain a single element or compound that is not mixed with any other substance. Pure substances have specific melting and boiling temperatures
• A homogeneous mixture has both uniform composition and uniform properties throughout, e.g saltwater and metal alloys
• A heterogeneous mixture has non-uniform composition and varying properties, e.g salad dressing, paint or garden soil
• Formulations have many different components (substances that make them up) in very specific proportions. Scientists spend a lot of time trying to get the right components in the right proportions to make the most useful product, like fuels, cleaning agents, alloys and foods
• Mixtures can be separated through…

  Filtration - separated insoluble solids from liquids

  Crystallisation - evaporates a solvent (liquid) leaving a solute (solid)

  Simple distillation - separates solvent from a solution as long as the solvent has a lower boiling point than the solute

  Fractional distillation - separates two or more substances from a liquid mixture
• The test for hydrogen is the squeaky pop test. Hold a lit splint near the gas and if hydrogen is present there will be a squeaky pop
• The test for oxygen is to hold a glowing splint near the gas and if oxygen is present the splint will relight
• The test for carbon dioxide is to bubble the gas through limewater. The limewater will turn milky/cloudy white if carbon dioxide is present
• The test for chlorine is to hold a piece of damp litmus near the gas. If chlorine is present it will bleach the litmus white