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

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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 qualityname of unitabbreviation
masskilogram/gramkg/g
lengthmeterm
temperatureKelvinK or °C
amount of substancemolemol
  • 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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