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Science 9

Science 9. Aim: To understand what Chemical Reactions are. Agenda. Science Sizzler Chemical Reaction Notes Bill Nye Video: Chemical Reactions Next Weeks class Unit Test Tues 29. Chemical Reactions. Takes place when two or more substances combine to form new substances

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Science 9

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  1. Science 9 Aim: To understand what Chemical Reactions are

  2. Agenda • Science Sizzler • Chemical Reaction Notes • Bill Nye Video: Chemical Reactions • Next Weeks class • Unit Test Tues 29

  3. Chemical Reactions • Takes place when two or more substances combine to form new substances • A chemical change in a substance results from a chemical change

  4. The launching of a space shuttle • 1,500,000 L of liquid Hydrogen and 545, 000L of liquid oxygen combine to form water. • This reaction produces enough energy to push a shuttle into orbit.

  5. Air Bags in a car • Contain explosive chemical sodium azide (NaN3(s)). • In an accident, the sodium azide reacts to produce large volumes of nitrogen gas and sodium • Sodium then reacts with another compound in the bag to make a less dangerous compound. • 50 grams of sodium azide can produce 50 L of nitrogen gas in milliseconds.

  6. Materials at the start of a reaction are called the Reactants • Materials at the end of a reaction are called the Products. • Ex. Wood + Oxygen Carbon dioxide + water + energy released + = separates reactants and products from each other.  = direction reaction goes (and means produces)

  7. Review Chemical reactions create new substances. Evidence of a reaction may include: • Colour change • Formation of an odour • Formation of solid or gas • Release or absorption of heat. There are exceptions, bubbling may just mean something is boiling

  8. Reactions that release or absorb heat • Exothermic reactions: Chemical reactions in which heat energy is released as a product. • Endothermic reactions: Chemical reactions in which heat energy is absorbed.

  9. Chemical Changes involving oxygen • Combustion • Oxygen reacts with a substance to form new substances and give of energy. • Fire is a common example. • Wood burns to give off heat and light, producing carbon dioxide and water • Could be considered first chemical reaction used by humans.

  10. 2. Corrosion • The slow chemical change that occurs when oxygen in the air reacts with a metal. • A common example is rusting. (oxygen reacts with iron to produce iron oxide) 3. Cellular respiration • Occurs in your body cells. • Sugars react with oxygen to produce energy, water, and carbon dioxide

  11. Comparing Ionic and Molecular Compounds Pg 153 – Examine the tables, and write your observations about molecular and ionic compounds.

  12. Practice Pg. 153 – 1,2, 4-6 Homework to be corrected in class P. 154 1-8, 10, 13

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