Introduction to Chemistry

SNC2DI/W

Organization of Matter

Physical Properties

• A physical property describes the substance

• E.g.– State– Hardness– Melting point– Boiling point– Odour– Solubility– Colour– Malleability– Ductility– Etc.

Chemical Property

• A chemical property is how the substance reacts to form a new substance.

• E.g.– How it reacts with acid– How it reacts with water– How it reacts with

oxygen– Etc.

Physical Change

• A physical change is when the original substance does not turn into a new substance but does change form.

• E.g.– Ripping a piece of paper– Dissolving a salt– Melting ice

Chemical Change

• When a substance changes from one substance into another, it is a chemical change.

• E.g.– Baking soda in acid– Iron exposed to oxygen– Combustion

How to Recognize a Chemical Change

• Clues that a chemical change has occurred.

1. A new colour appears

2. Heat or light is given off

3. Bubbles of gas are formed

4. A precipitate (solid) forms in a liquid

5. The change is difficult to reverse

E.g. 2H2(g) + O2(g) 2H2O(l)

Chemical Tests

• You can use chemical change to perform a chemical test to determine if a substance is present.

– Glowing splint used to indicate if oxygen is present

– A burning splint is used to indicate if hydrogen is present

– Limewater can be used to indicate if carbon dioxide is present

– Cobalt chloride paper can be used to indicate if water is present

– A flame test can tell which type of metal is present

Flame test for Li

Do you remember?

• WHMIS?– Provides Canadian workers with the

information on the safe use of hazardous materials in their workplace.

• MSDS?– Material safety data sheet

1. Classify each of the following observations as an example of either a chemical property or a physical property. [K]

a. Propane, leaking from a damaged tank, ignites easily.

b. Silver jewellery tarnishes (darkens) in air

c. Spilled oil generally floats on the surface of water.

2. What type of change is describes in each of the following? [K]a. A loud pop is heard when a lit match is placed inside of a test tube.

b. Air is often blended into ice cream in order to give it a lighter quality.

3. Drain cleaners often produce a great deal of heat as they unclog drains. Is the action of the drain cleaner a chemical or physical change? [A]

1. Over time, crusty scales form on the heating coils inside a kettle. These can be removed by covering the coils with vinegar. As the scales disappear, bubbles of gas are observed. Does this method of cleaning a kettle represent a physical or chemical change? Explain. [A]

Credits

• http://mr.fusco.ca • http://commons.wikimedia.org/wiki/File:Snow_crystals_2b.jpg • http://commons.wikimedia.org/wiki/File:Magnesium_Sparks.jpg • http://commons.wikimedia.org/wiki/File:Melting_icecubes.gif • http://commons.wikimedia.org/wiki/File:Lighting-match.gif • http://commons.wikimedia.org/wiki/File:FlammenfärbungLi.png• http://commons.wikimedia.org/wiki/File:Cr-Ac-OH-

MSDS_SigmaAldrich.pdf• http://commons.wikimedia.org/wiki/File:WHMIS_Class_F.svg• http://commons.wikimedia.org/wiki/File:WHMIS_Class_D-3.svg