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)

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

• 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