4/17/09
Post date: Apr 17, 2009 12:32:36 AM
Bell Ringer: Give two examples of physical properties.
Changes of matter - Group presentations
Physical changes
Affects one or more physical properties of a substance without changing the identity of the substance
Melting - change of state, but same substance
Cutting - change of size, but same substance
Crushing - change of shape, but same substance
Dissolving is a physical change
Sugar dissolves in water, but you can still taste it
Water molecules spread out the molecules of the other substance, but don't alter them
Chemical changes
One or more substances are changed into entirely new substances with different properties
Can be detected by a change in taste, smell, color, etc.
Cannot be reversed by physical changes
Breaking down mixtures and compounds
Mixtures can be physically separated
Some compounds can be broken down through chemical changes
Signs of a chemical change
Different color
Gas is produced
A precipitant is formed
Each sign indicates a new substance is present
Observations - physical or chemical change?
Ice melting - physical (all changes of state, such as solid to liquid, are physical changes)
Baking soda and vinegar - chemical (bubbles form, meaning the new substance is a gas)
Milk and lemon juice - chemical (forms a precipitant, meaning it gets chunky)
Food coloring and water - physical (dissolving is a physical change, water just spreads the other molecules out)
Page 64: 1-8 due Tuesday
Chapter 2 Test Wednesday