Science test

• Physical change


  A substance changes in size, shape or state, or two substances are mixed. No new substance is formed.
• Chemical change


  Gases, heat or light are often released, and the change usually can't be undone. A new substance is formed.
• What happens when sugar dissolves in water

  1. A lump of sugar is added to a beaker of water

  2. The sugar starts to dissolve

  3. The two types of molecule are evenly spread
• Chemical element

  A substance made up of only one type of atom
• Molecules

  Small groups of atoms joined together by chemical bonds, the atoms are joined together in continuous frameworks
• Lattices

  Orderly arrangements of atoms, ions, or molecules in solids
• Properties of typical metals

  • Shiny or Glossy
  • Conduct Electricity
  • Can be flattened into sheets
  • Can be stretched into threads or wires
• Compounds


  Molecules that are two or more types of atoms that are chemically bonded together
• Physical change


  Altering the appearance or state of a substance without changing what it's made of
• Chemical change


  Creating entirely new substances by rearranging the atoms of the original substance
• Physical change


  • Melting ice into water, crushing a can, boiling water into steam
• Chemical change

  • Rusting of iron, burning wood, digestion of food in the stomach
• Physical changes

  The particles in a substance don't change how they're arranged, they just move differently
• Signs of a chemical change

  • Formation of gas
  • Change in color
  • Formation of a precipitate
  • Release or absorption of heat
  • Production of light
  • Change in odour
• Chemical changes

  Particles rearrange to form entirely new substances with different properties. Bonds break and new bonds form, resulting in the creation of different materials.
• Physical changes alter a substance's appearance without altering its composition, while chemical changes create new substances by rearranging its atoms.
• Element

  A substance composed of atoms with the same number of protons in their atomic nuclei, thus sharing the same atomic number. It cannot be broken down into simpler substances by ordinary chemical means.
• Molecules

  Tiny units formed by the chemical bonding of atoms
• Properties typical of metals


  • Good conductors of electricity and heat
  • Malleable (can be hammered into thin sheets)
  • Ductile (can be drawn into wires)
  • Shiny appearance
  • High-density and melting point
  • Usually solid at room temperature (except mercury)
• Properties typical of non-metals


  • Poor conductors of heat and electricity
  • Brittle when solid
  • Lacklustre (dull) appearance
  • Low density and melting point
  • Exist in various states (solid, liquid, gas) at room temperature
  • Tend to gain electrons in chemical reactions (except for hydrogen)
• Elements


  Pure substances made of one type of atom
• Compounds


  Substances made of two or more elements chemically combined
• Mixtures

  Combinations of substances not chemically bonded
• A compound is made up of elements bonded together in fixed proportions, as shown by its chemical formula.