1.1: science basics
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
\ 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 |
|---|---|---|
| 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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