Physical and chemical changes

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Physical Chemical Changes

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Physical and chemical changes

  1. 1. PHYSICAL and CHEMICAL CHANGES
  2. 2. Physical Changes <ul><li>A physical change occurs when a substance changes, but no </li></ul><ul><li>new substance is formed. </li></ul><ul><li>Physical changes occur when the state of a substance </li></ul><ul><li>changes (eg melting, evaporation, freezing, condensing) or a </li></ul><ul><li>substance is crushed, ground or cut into smaller pieces. </li></ul><ul><li>Physical changes are often easy to reverse. </li></ul>
  3. 3. Change of State Remember The particles in a solid are close together and vibrate. The particles in a liquid are further apart and slide over each other. The particles in a gas are far apart and bump into each other as they move quickly.
  4. 4. <ul><li>The following are examples of physical change. </li></ul><ul><li>• A plate is dropped and shatters. </li></ul><ul><li>• Ice melts. </li></ul><ul><li>• Water boils. </li></ul><ul><li>• Wax melts. </li></ul><ul><li>• Iodine sublimes. </li></ul>
  5. 5. Chemical Changes <ul><li>A chemical change or chemical reaction occurs </li></ul><ul><li>whenever a new substance forms. </li></ul><ul><li>Evidence that a new substance is formed are – </li></ul><ul><li>a change in colour. </li></ul><ul><li>a gas given off. </li></ul><ul><li>a new solid forms. </li></ul><ul><li>a change in temperature. </li></ul>
  6. 6. <ul><li>The following are examples of chemical change. </li></ul><ul><li>• Wood burns </li></ul><ul><li>• An egg is cooked to become a white and yellow solid. </li></ul><ul><li>• A metal panel on a car rusts. </li></ul><ul><li>• Fireworks explode. </li></ul><ul><li>• Concrete hardens. </li></ul><ul><li>• An egg cooks. </li></ul><ul><li>• Paper burns. </li></ul>
  7. 7. Questions <ul><li>1. Label the following diagram replacing each letter A – G with a word </li></ul>A = solid B = liquid C = gas D = melting E = evaporation F = condensing G = freezing
  8. 8. Questions <ul><li>Classify the following examples as physical or chemical changes. </li></ul><ul><li> a) Water freezes to make snow. </li></ul><ul><li>b) A cake cooking. </li></ul><ul><li>c) Food is digested. </li></ul><ul><li>d) A puddle of water evaporates. </li></ul><ul><li>e) Lighting the gas in a bunsen burner. </li></ul><ul><li> f) Lighting a match. </li></ul><ul><li>g) Steam condensing on a mirror. </li></ul><ul><li>h) Melting a gold nugget to make a gold bar. </li></ul><ul><li>i) Dynamite exploding. </li></ul><ul><li>j) Burning your toast. </li></ul><ul><li>k) Water freezes to make ice cubes. </li></ul><ul><li>l) Ice cream melting. </li></ul><ul><li>m) Iron rusting </li></ul>a) Physical b) Chemical c) Chemical d) Physical e) Chemical f) Chemical g) Physical h) Physical j) Chemical i) Chemical k) Physical l) Physical m) Chemical

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