CHEM 107 Lecture Notes - Lecture 2: Chemical Bond, Intensive And Extensive Properties, Physical Property

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Published on 24 Aug 2016
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Scientific method
Observe-looking for a problem to solve
Form a hypothesis-educated guess
Gather data- observation/experiment/test
Analyze and refine hypothesis
Theory vs law
Theory-attempts to explain why something happens
oCan change
oRelativity, evolution, gravity
Law-describes what happens
oDoes not change
oGravity, motion, thermodynamics
Theory of gravity and law of gravity are separate
Matter- “stuff” everything is made of
Phases of matter
Shape Volume Particle motion Particle structure
Solid Fixed Fixed Slow Rigid
Liquid Variable Fixed Faster Fluid/little
Gas Variable Variable Fastest Fluid/no structure
Plasma-gas that’s so hot, the electrons have been removed from the atom
Mass vs Weight
Mass-amount of matter in an object
Weight- effect of gravity on an object
oNot a constant
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Law of conservation of matter
Matter is neither created or destroyed in a chemical process
Atoms vs Molecules
Atom-smallest particle of an element that retains the properties of the element.
o Ex. Au, C, K
Molecule- 2 or more atoms joined by a chemical bond.
oEx. H20, F2, CO2
Classifying matter
Pure substance-composition is constant regardless of source
o2 types of pure substances
oElements- cannot be broken down into simpler substances. Ex.-Fe, Al, O2, H2
oCompound- can be broken down into simpler substances. Ex.-NaCl, H2O
Mixture-composition is dependent on the source
oCan be separated by physical properties with evaporation or filtration
o2 types of mixtures
oHeterogeneous-variable composition. Ex. Mud, food, concrete
oHomogeneous- uniform compostion. Solutions. Ex. Sugar water, saltwater, apple juice
Physical vs. chemical properties and changes
Physical property- independent of chemical reactivity. Ex color, shape, volume, boiling/melting
Physical change- change in physical properties. Ex- cutting, melting, evaporation
Chemical property- tendency of a substance to react with other substances. Ex. Fe will rust, Au
does not react
Chemical change- change in chemical composition. Ex.- H2O2 decomposes into H2O and O2
Extensive vs intensive properties
Extensive- properties that are dependent on the amount of the substance. Ex- mass, volume,
Intensive- independent amount of substance. Ex- density, melting/boiling point, temperature
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