Physical and Chemical Properties and Changes Page 18 and 19 Page 28 – 30 Page 34 – 35 Page 38 - 39

Page 18 - 19 Chemical Properties of Matter When one substance can interact with another, the characteristic behaviour is called a chemical property. Ie. Dynamite explodes when exposed to a flame and mixes with oxygen in the air.

Vocabulary Chemical Property A chemical property describes the behaviour of a substance as it becomes a new substance. Combustibility Combustibility is a property that describes the ability of a substance to react with oxygen to produce carbon dioxide, water and energy. Combustible is flammable; non-combustible is nonflammable!

Reaction with acid Another chemical property of matter is reaction with acid. For example, when magnesium metal is added to acid, it produces bubbles of gas and the metal disappears. Limestone is identified by it’s reaction to acid; bubbles of gas are produced when they come in contact. Metals and Nonmetals Matter can be grouped as metals and nonmetals. Mixtures of metals are alloys. Examples are: braces, cooking pots and airplanes.

Physical and Chemical Changes ARE NOT THE SAME as Physical and Chemical Properties we have studied so far.

A burning candle – what happens? As the candle burns, the wax melts (a solid becomes a liquid), and then it hardens (a liquid becomes a solid). These are physical changes. The wax also combusts producing heat and light. This chemical change involves the wax becoming carbon dioxide, water and energy.

Physical and Chemical Changes (Not the same as Phys. and Chem Physical and Chemical Changes (Not the same as Phys. and Chem. Properties) Physical Change: The substance involved remains the same, even though it may change state or form. Ex. Pour melted chocolate on ice cream. It still tastes the same because the particles have not changed, it just hardened (changed state) because the ice cream was cool. Most physical changes are easy to reverse.

Chemical Changes: The original substance is changed into one or more different substances that have different properties. Examples: Burning, Cooking, Rusting… The formation of water from hydrogen and oxygen. The formation of rust from iron and oxygen. Chemical changes are difficult to reverse.

There are usually clues that a chemical change has happened: A new colour appears. Heat or light is given off. Bubbles of gas are given off. A solid material (called a precipitate) forms in a liquid. The change is difficult to reverse.

Assignment 1. Copy Table 2, page 30 in your notebook. 2. Read pages 28-30 and on page 30 answer questions 1-4. Copy the questions and the answers into your notebook.

1. Explain how a physical change differs from a chemical change. Page 30 questions 1-4 1. Explain how a physical change differs from a chemical change. Chemical changes involve production of a new substance with new properties. No new substances are produced in physical changes.

2. a) Garbage rotting chemical b) Cutting up carrots physical c) A silver spoon turning black d) Making tea from tea leaves e) Bleaching a stain f) Boiling an egg

Question 3 Changes occur more quickly at high temperatures. Putting candles together tends to concentrate heat more and the candles will be at a higher temperature. For emergencies, non-dripping and non-smoking candles should be kept on hand. (or battery operated)

Question 4 Evaporation, mixing, and condensation are physical changes. Combustion, catalytic conversion and rusting are chemical changes.

Sample Chemical Changes (Always involve the production of a new substance.) Ex. 1: H + O  H2O (water) gas gas liquid Reactants: Left side Products: Right side Ex. 2: C + 2O  CO2 (carbon dioxide) Ex. 3: 6C + 12H + 6O  C6H12O6 (sugar) Ex. 4: 3C + 8H  C3H8 (Propane)