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5.1 Substances in the Earth’s crust

5.1 Substances in the Earth’s crust. The Earth’s crust consists of many different substances. 5.2 What is a compound?. A compound is a substance containing two or more elements chemically joined together. 5.3 Making and breaking the compound water.

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5.1 Substances in the Earth’s crust

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  1. 5.1 Substances in the Earth’s crust • The Earth’s crust consists of many different substances.

  2. 5.2 What is a compound? • A compound is a substance containing two or more elements chemically joined together.

  3. 5.3 Making and breaking the compound water • When hydrogen combines with oxygen to form the compound water, a lot of energy is given out. • Hydrogen + oxygen water • Electrical energy can be used to break down water into hydrogen and oxygen. • Water hydrogen + oxygen Electrical energy video 5.3

  4. 5.4 What is a mixture? • A mixture contains two or more elements or compounds not chemically joined together.

  5. 5.5 Comparing properties of carbon/oxygen mixture and carbon dioxide

  6. Molecule (分子) • Some atoms can join together to form a group called a molecule. • Molecule of an element • Molecule of a compound

  7. 5.5 Comparing properties of carbon/oxygen mixture and carbon dioxide • When carbon and oxygen are mixed together without heating, the carbon atoms and oxygen molecules are still present in the mixture. • When carbon is heated in oxygen, carbon atoms and oxygen atoms join together to form carbon dioxide molecules. • The carbon dioxide molecules are different from the carbon atoms and oxygen molecules. • Properties of carbon dioxide are different from those of carbon and oxygen. ani 5.5

  8. 5.6 Comparing properties of iron/sulphur mixture and iron(II) sulphide • Iron and sulphur still retain their original properties in the mixture. However, when they combine to form a compound, the compound shows new properties.

  9. Comparing properties of hydrogen/oxygen mixture and water • Appearance • Hydrogen : colourless gas • Oxygen : colourless gas • Water : colourless liquid

  10. Comparing properties of hydrogen/oxygen mixture and water(chemical properties) • Inserting a burning splint • Hydrogen : a ‘pop’ sound • Oxygen : burn more violently • Water : extinguish the fire

  11. 5.7 Useful web links • Materials on mixtures • http://library.thinkquest.org/3659/atommole • Comparison of mixtures and compounds • http://www.chem.vt.edu/RVGS/ACT/notes/Mixtures_and_Compounds.html

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