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Chemical Properties and Changes (Ch 7 Sec 3:pgs 194-199) (Chemical…
Chemical Properties and Changes (Ch 7 Sec 3:pgs 194-199)
Chemical Properties (pg 194-195)
Chemical Properties : describe matter based on its ability to change into new mater that has different properties.
Characteristic Properties: most useful in identifying a substance
ability to participate in chemical reactions
same no matter the size of sample
scientists rely on characteristic properties to identify and classify substances
describes a substance's ability to participate in chemical reactions
Are not as easy to observe
Can see flammability only while it is burning
Can observe nonflammability only when it won't burn
Substance always has chemical properties (still flammable even when it's not burning)
Which chemical changes will/will not occur
Flammability = the ability of a substance to burn
Nonflammability = cannot burn
Reactivity = the ability of 2 or more substances to combine and form one or more new substances (ex. rust)
Physical Versus Chemical Changes (pg 198)
IMPORTANT QUESTION
Did the composition change?
composition is the type of matter that makes up the object and the way that the matter is arranged in the object
Most chemical changes are not easily reversed
Firework exploding = impossible to reverse, even if you collected all the materials
Chemical Changes and New Substances (pg 196)
Happens when one or more substances are changed into new substances that have new and different properties.
Often harder to reverse (ex. baking a cake)
process where substances actually change
eat food = digestion
using batteries
bake cake
Signs
change in color or odor (smell)
production of heat
fizzing and foaming
sound or light
