Topic 2 - Atoms, elements and molecules

• Atoms on a picture look like single circles
• Molecules of a compound on a picture look like two small circles stuck together or a small circle
• Molecules of a mixture is just molecules but different kinds of molecules in the picture
• Molecules of a compound look like a big ball and then two small circles
• Periodic table: 118 elements
• Everything is made up of atoms
• Mixture: 2+ elements not joined together
• Element: simple substances made of only one kind of atom
• Compound: 1+ element joined together
• Molecule: A group of atoms bonded together
• Metals obtained from compounds are minerals
• Metals have a high melting point, are malleable and ductile, shiny, good conductors of heat and electricity.
• Copper, zinc and iron are metals
• Non-metals: low melting point, brittle, not shiny, good insulators of heat and electricity.
• Sulphur, oxygen, iodine and carbon are non-metals
• Zinc + oxygen -->?

  Zinc oxide
• Sodium + carbon -->?

  Sodium carbonate
• Chemical reactions always form 1+ new substances
• Physical reactions form no new substances
• Heat is often needed to start a chemical reaction
• Signs of a chemical reaction: colour change, gas being given off, an energy change and a solid forming in a liquid.