Natural Science

• Mixture


  Made up of two or more different substances, containing solids, liquids and/or gases, not joined together chemically, simply mixed together
• Pure substance


  Made up from only one type of particle, e.g. water
• Impure substance


  Made up of two or more substances, e.g. air
• Types of mixtures


  • Solid and solid
  • Solid and liquid
  • Solid and gas
  • Liquid and liquid
  • Liquid and gas
  • Gas and gas
• Mixture of a solid and a solid


  • Soil (rocks, sand, grass, organisms)
• Solution


  Mixture of a solute (substance that dissolves) and a solvent (substance that does the dissolving), e.g. salt and water
• Suspension


  Mixture of solid particles suspended in a liquid, e.g. sand in water
• Mixture of a solid and a gas


  • Smoke from a fire (soot particles suspended in air)
• Emulsion


  Mixture of liquids suspended in liquids, e.g. milk (water and fatty oil)
• Solution


  Mixture of liquids where one substance dissolves into another, e.g. vinegar and water
• Mixture of a gas and a gas

  • Air (nitrogen, oxygen)
• Mixture of a liquid and a gas


  • Clouds, fog, mist (water droplets suspended in air)
• Separation methods


  • Hand-sorting
  • Decanting
  • Using a magnet
  • Evaporating
  • Filtration
  • Distillation
  • Chromatography
• Hand-sorting


  Separating solid particles that have different sizes, colours, textures or shapes and are easy to handle
• Hand-sorting


  • Sorting fruit by size and quality
• Decanting


  Separates two liquids which have different weights or separating liquid without disturbing the sediments that have settled at the bottom
• Decanting


  • Pouring water out of a bucket containing mud that has settled at the bottom
• Using a magnet


  Magnets attract iron, steel, and nickel, so can be used to separate magnetic materials from a mixture
• Using a magnet


  • Removing magnetic objects from waste dump
• Evaporating


  Using heat to separate soluble solids from liquids
• Evaporating


  • Collecting salt from seawater, by letting the water evaporate
• Filtration


  Insoluble materials won't pass through the tiny holes of the filter paper and so are separated from the soluble materials
• Filtration


  • Separating rock salt
• Distillation


  Separates a solvent from a solution through evaporation and condensation
• Distillation


  • Separating seawater (salt remains in the flask, distilled water collected)
• Chromatography


  Separating different dyes in ink as they move through paper at different rates based on solubility
• Chromatography


  • Separating dyes in ink
• Physical properties


  Characteristics of a material that allow us to determine how a material looks, feels, behaves and what it can be used for
• Examples of physical properties

  • Strength
  • Boiling and melting points
  • Flexibility
  • Electrical conductivity
  • Heat conductivity
• Factors such as cost, colour, texture, and mass of materials also need to be taken into consideration when choosing a material for a particular purpose
• Brittle


  A material that is hard, but easily broken
• Density


  The mass of a substance divided by its volume. The denser a substance is, the heavier it feels for its size. It is measured in kilograms per metre cubed (kg/m3)
• Ductile


  A material that can be stretched into wires
• Dull


  A surface which does not reflect light. Not shiny
• Hard


  A material that is firm, not easily broken, cut or pierced
• Insulator


  A material that electricity and heat cannot pass through easily
• Magnetic


  A material that can be attracted by a magnet or made into a magnet. Examples are iron, steel, cobalt and nickel. All magnetic materials are metals, but not all metals are magnetic
• Malleable


  A material that can be hammered or pressed into different shapes
• Shiny


  A surface which reflects light. You can sometimes see your reflection on these surfaces
• Soft


  A material that is easy to mould, cut or fold. It is not firm to touch