Introduction to Chemistry

SNC2DI

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 a description of 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

Homework

• Read section 5.1

• Answer questions 2-8 on page 178

Credits

• 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