introductory terms
- chemistry: the study of the properties and behavior of matter
- central to our fundamental understanding of many science-related fields
scientific laws and theories
- law: a statement about what happens in nature that seems to always be true
- allows predictions about how a natural system will work or behave
- does not explain how a process takes place
- theory: an explanation for a natural phenomenon
- eg. big bang theory (broad explanation)
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observations and types of data
- quantitative measurements
- involve numbers and units
- objective and precise (eg. -12°C, 100kg, 14cm)
- must include units
- qualitative measurements
- descriptions
- subjective and imprecise (eg. red, hot, bubbly, heavy)
- perception-based
- observation: information gathered directly through the five senses
- inference: a logical explanation for an observation based on context, prior knowledge, and experience
- eg. observation—the fire alarm is oging off
- possible inferences: the building is on fire, there is a fire drill, someone pulled the fire alarm
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units of measurement—SI units
- based on the Système International d’Unités (International System of Units)
- there is a different base unit for each quality (eg. length, weight)
SI base units
physical quality | name of unit | abbreviation |
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mass | kilogram/gram | kg/g |
length | meter | m |
temperature | Kelvin | K or °C |
amount of substance | mole | mol |
- mass and length
- mass: the amount of matter (stuff) in an object—not weight!
- length: a measure of distance
- volume
- not a base unit in the SI sy31dx2stem
- derived unit from length; most commonly used metric units are liters (L) and milliliters (mL)
- temperature
- temperature: the measure of the average kinetic energy of the particles that make up an object
- the Kelvin and Celsius temperature scales are used in science, not Fahrenheit
- heat flow at a higher rate = higher temperature and vise-versa
- the Celsius scale is based on the physical properties of water
- density
- derived unit from mass/volume (D=M/V)
- commonly used units: g/mL or g/cm^3
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