Science

• Compounds


  Substances made up of two or more elements joined together
• When two or more atoms join together, a molecule is made
• Chemical bond


  The "join" between atoms in a molecule
• Compounds are formed when atoms from different elements join together
• Types of substances


  • Element (made of atoms of one type)
  • Molecule (made of atoms of one type joined together)
  • Compound (made of atoms of different types joined together)
  • Mixture (made of two or more substances not chemically joined)
• Compounds are formed from chemical reactions where reactants combine to form new products
• Atoms


  Tiny particles that make up all matter
• Dalton was the first modern scientist to try to explain things about atoms
• Element


  A substance that contains only one type of atom
• Elements


  • Copper
  • Aluminium
  • Iron
  • Oxygen
  • Nitrogen
• Element symbol


  A one or two letter abbreviation for an element
• There are over 100 different elements
• Mixture


  A substance made up of two or more different substances that are not chemically joined
• A pure substance is made up of only one type of element or compound
• Sea water and air are examples of mixtures
• A mixture has the properties of its constituent parts
• In a chemical reaction, atoms rearrange themselves but are not created or destroyed
• The mass does not change in a chemical reaction
• Chemical reactions involve a change in energy, which can cause temperature changes
• Visible changes can occur in a chemical reaction mixture
• Specular reflection


  Reflection off a smooth, shiny surface where the angle of incidence equals the angle of reflection
• Diffuse reflection


  Reflection off a rough surface where light is scattered in many directions
• Law of reflection


  Angle of incidence = angle of reflection
• Normal


  A line perpendicular to a surface
• Refraction


  The bending of light as it passes from one medium to another
• Light bends towards the normal when going from a less dense to a more dense medium, and away from the normal when going from a more dense to a less dense medium
• Light travels fastest in a vacuum, at a constant speed of 3 x 10^8 m/s
• Living things are made of cells
• Vacuum


  Where there is nothing at all - no air, no particles, nothing
• Space is mostly a vacuum
• Speed of light in a vacuum

  3 x 10^8 m/s (three hundred million metres per second)
• The speed of light in a vacuum is always 3 x 10^8 m/s
• Light from the Sun gets to Earth in only 8.3 minutes - even though it's 150,000,000 km away
• Nothing travels faster than light in a vacuum
• Key information to learn

  • 150,000,000 km
  • 8.3 minutes
  • Speed of light waves in a vacuum= 3 x 10^8 m/s
• Although light is slower when it has to travel through matter (like air or water), it's still so fast that its movement appears instant to the human eye
• Living thing


  Another word for organism
• All organisms are made up of tiny building blocks known as cells
• Cells can be seen through a microscope, but it helps if you stain them first (using a coloured dye)
• Similarities between animal and plant cells


  • Nucleus
  • Cytoplasm
  • Cell Membrane