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2.1 Classifying Matter (Elements (Atom:smallest particle of an element …
2.1 Classifying Matter
Pure Substances
matter that always has exactly the same composition(also called simply substance)
KEY: Every sample of a given substance has the same properties because a substance has a fixed, uniform composition.
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Elements
Atom:smallest particle of an element
- Ex. Cutting copper wire into small pieces, eventually end up with extremely tiny copper atoms.
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Element: A substance that cannot be broken down into simpler substances. - Ex. only about 100
- no 2 elements contain same type of atom
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Examples of Elements
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Summary statement: Elements come in different forms at room temperature, but most are solid.
Symbols for Elements
1813, Jons Berzelius suggested chemists use symbols to represent elements
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Compound
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Definition: Substance that is made from two or more simpler substances and can be broken down into those simpler substances. Simpler substances either elements or other compounds.
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Homogeneous Mixture:
Define: substances are so evenly distributed that it is difficult to distinguish one substance in the mixture from another.
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Solutions, suspensions, colloids:
KEY: Based on the size of it's largest particles, a mixture can be classified as a solution, suspension, or colloids.
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Solutions:
Define: When substances dissolve and form a homogeneous mixture, that mixture that forms is the solution.
- Ex. spoonful of sugar in hot water
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Suspensions:
Define: is a heterogeneous mixture that separates into layers over time.
- Ex. if you shake up a container of sand and water , the sand mixes with the water and forms a suspension. Overtime, suspended particles of sand settle to the bottom of the container.
Colloids:
Define:Colloids: contains some particles that are intermediate in size between the small particles in a solution and the larger particles in a suspension.
- Ex. milk processed and not processed(cream), fog of water droplets in air
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