1.S: Matter and Measurement (Summary)
- Page ID
- 91131
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1.1: The Study of Chemistry
The Molecular Perspective of Chemistry
- Matter – physical material of the universe, has mass and takes up space
- Atoms – the building blocks of matter
- Molecules – groups of combined atoms
Why Study Chemistry?
- important in understanding our world
- chemistry is the central science
- many various subjects have some kind of relation to chemistry
1.2: Classification of Matter
States of Matter
- states of matter: liquid, solid, and gas
Pure Substances and Mixtures
- pure substance – matter that has a fixed composition and distinct properties
- substances can be classified as elements or compounds
- elements – composed of only one atom
- compounds – two ore more elements
- mixtures – combination of two or more substances
- heterogeneous – mixtures that are not uniform throughout
- homogeneous – mixtures that are uniform throughout; also called solutions
Separation of Mixtures
- components in a mixture retain their own properties
- mixtures can be separated by using the different properties of each substance
- types of separation: filtration, distillation, chromatography
Elements
- over 90% of earth’s crust consists of oxygen, silicon, aluminum, iron, and calcium
- human body consists of 90% of oxygen, carbon, and hydrogen
Compounds
- law of constant composition (law of definite proportions) – elemental composition of a pure compound is always the same
1.3: Properties of Matter
- physical properties – properties measured by not changing the identity and composition of the substance
- chemical properties – the way a substance may change or react to form other substances
- intensive properties – identify substances
- extensive properties – amount of substance
Physical and Chemical Changes
- physical change results in a change in appearance but not composition
- changes of state are physical changes
- chemical changes (chemical reactions) results in a chemically different substance
1.4: Units of Measurement
SI Units
- seven base units
| Prefix | Abbreviation | Meaning |
|---|---|---|
| Mega- | M | 106 |
| Kilo- | K | 103 |
| Deci- | D | 10-1 |
| Centi- | C | 10-2 |
| Milli- | m | 10-3 |
| Micro- | µa | 10-6 |
| Nano- | n | 10-9 |
| Pico- | p | 10-12 |
| Femto- | f | 10-15 |
Length and Mass
-
- SI base unit for length is the meter (m)
- Mass is a measure of the amount of material in an object
Temperature
- Celsius and Kelvin scales are used commonly in science
- Both have equal sized units
- K = °C + 273.15
- °C = (5/9)(°F –32)
- °F = (9/5)(°C) + 32
Derived SI Units
Volume
- SI unit is cubic meter
- Equipment to measure volume accurately : syringes, burets, and pipets
Density
- density = mass/volume
1.5: Uncertainty in Measurement
1.5.1 Precision and Accuracy
- precision – the closeness of individual measurements to one another
- accuracy – the correctness of individual measurements
Significant Figures
- Nonzero digits are always significant
- Zeros between nonzero digits are always significant
- Zeros at the beginning of a number are never significant
- Zeros that fall both at the end of a number and after the decimal point are always significant
- When a number ends in zeros but contains no decimal point, the zeros may or may not be significant
- Scientific notation can be used to get the correct significant numbers
Significant Figures in Calculations
- the number of significant figures is determined by the number that has the fewest significant figures in the calculation
1.6: Dimensional Analysis
- aid in problem solving
- conversion factor – fraction where the numerator and denominator are the same quantity