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Reactions and Corrosion

3.3 – pg. 99-100. Reactions and Corrosion. Think back to last class: Do you remember the rotting apple? What changes occur as the apple rots? Chemical Change: Ethene gas is produced as the apple rots Physical Change: Apple juices evaporate (a change of state) .

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Reactions and Corrosion

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  1. 3.3 – pg. 99-100 Reactions and Corrosion

  2. Think back to last class: Do you remember the rotting apple? What changes occur as the apple rots? Chemical Change: Ethene gas is produced as the apple rots Physical Change: Apple juices evaporate (a change of state)

  3. Chemical and Physical Changes and ENERGY! • Chemical and physical changes can happen at the SAME TIME! • Rotting apple • Explosions • REVIEW: Physical and Chemical changes are accompanied by ENERGY CHANGES!

  4. Exothermic Reactions • Involves the release of energy in the form of heat and light • “exo-” means “leaving” • Causes the temperature of the immediate surroundings to rise Reactants  Products + Heat Examples: • Explosions

  5. Endothermic Reactions • Involves the absorption of energy • “endo-” means “entering” • Causes the temperature of the surrounding environment to cool Reactants + Heat  Products

  6. So how can our knowledge of chemical changes be used?

  7. 1. CORROSION • Corrosion: the process of metals breaking down Example 1: Steel ferries in BC are prone to rusting • Rust: the product of a chemical change between iron and water • Solution: apply several coats of paint or attach zinc metal to the hull (the Zn will erode instead of the hull)

  8. Example 2: Aluminum corrosion • Al corrodes easily BUT this is a benefit! • The product, aluminum oxide, forms a smooth surface that prevents further corrosion! Example 3: Colour Change • Some corrosion can improve appearances • The blue-green “patina” that forms on copper contains many corrosion products

  9. 2. Using Chemical Change for Traditional Products • First Nations of Canada use traditional chemical technologies to manage natural resources • tanning hides, making dyes and medicines, and preserving food Example 1: Drying fish in smokehouses • Drying is a physical change that removes water from the fish • Smoke causes chemical changes in the meat that kill bacteria

  10. Example 2: Burning oolichan oil • Improves the flavour of smoked meat and provides a dietary source of fat, iodine, and vitamins • Contains so much oil that the fish will burn if set on fire

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