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Topic 4.0 – Chemical Reactions

Topic 4.0 – Chemical Reactions. Chemical Reactions. Chemical reaction – a reaction where NEW products are formed What are the products of the following? Ex. Baking cookies Combustion of wood Reactants – what is reacting in a reaction

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Topic 4.0 – Chemical Reactions

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  1. Topic 4.0 – Chemical Reactions

  2. Chemical Reactions • Chemical reaction – a reaction where NEW products are formed What are the products of the following? Ex. Baking cookies Combustion of wood Reactants – what is reacting in a reaction Products -what is made from a reaction

  3. Chemical Reactions • Chemical reactions are represented by words or chemical formulas Ex. Combustion propane + oxygen  carbon dioxide + water REACTANTS PRODUCTS “and” “produces”

  4. Chemical Reactions • When writing the formula equation, make sure to label the states that you know. (g) – gas (l) – liquid (s) – solid (aq) – solution Ex. Copper hydrogen

  5. Ex. Write a chemical formula equation when copper (II) sulphide and zinc react producing zinc sulphide and copper metal.

  6. Chemical Reactions • Evidence of chemical reactions are: • A color change • Odor change • Formation of a solid (precipitate) • Formation of a gas (bubbles) • Release or absorption of heat (“feels hot” or “feels cold”)

  7. Chemical Reactions Energy Changes Exothermic– when a reaction releases energy (it exitsthe reaction) Ex. Combustion Endothermic – when a reaction requires energy (it enters the reaction Ex. Cold pack

  8. Chemical Reactions Types of Reactions • Combustion - energy is released chemical + oxygen  carbon dioxide + water + energy • Corrosion (slow reaction) metal + oxygen  iron (II) oxide (rust) *Are always required or made in combustion

  9. Chemical Reactions Types of Reactions • Cellular Respiration – when glucose is used in the body to produce energy glucose + oxygen  carbon dioxide + water + energy

  10. Conservation of Mass Types of Systems • Open – when matter and energy can enter and leave • Closed – when energy can enter/ leave but matter cannot • Isolated – when matter and energy cannot enter or leave

  11. Conservation of Mass • Law Conservation of Mass – states that “matter cannot be created nor destroyed” mass before reaction = mass after the reaction *when the reaction takes place in a closed system * (so gases cannot leave) Ex. If 10.0g of oxygen is required to burn 1500g of wood, then what mass of products is made?

  12. Ex. 5.0g of zinc and 8.0g of hydrogen chloride are mixed to produce 11.6g of zinc chloride and hydrogen. a) What is the chemical equation to represent this reaction? Label the reactants and products. b) What mass of hydrogen is produced? c) Based on the products made, what observation could tell you it was a chemical reaction?

  13. Increasing Rates of Chemical Reactions • We can increase the speed at which a reaction takes place by: • 1. Adding a catalyst – speeds up reaction, but is not used up in the reaction Ex. Enzyme • 2. Increasing the concentration - increase the amount of reactants reacting • 3. Increasing temperature – the particles will collide more frequently, producing a reaction • 4. Increasing surface area- breaking reactants into smaller portions, causes more places to react

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