Overview
This lecture covers the basics of measurement in science, focusing on physical quantities, their classification, units, and various systems of units, including the SI system.
Qualitative vs. Quantitative Observations
- Qualitative observations describe qualities like color, smell, or taste and cannot be measured numerically.
- Quantitative observations involve measurements such as mass, volume, or density that can be assigned numbers and units.
Physical Quantities
- Physical quantities are properties of matter or phenomena that can be measured, like mass or length.
- Measuring physical quantities requires both a numerical value and a unit (e.g., 5 meters).
Measurement Process
- Measurement involves comparing a quantity to a standard of the same kind (the unit).
- The result expresses how many times the standard unit fits into the quantity measured.
Types of Physical Quantities
- Base quantities are fundamental and independent, including length, mass, time, electric current, temperature, amount of substance, and luminous intensity.
- Derived quantities are formed by multiplying or dividing base quantities (e.g., area = length × length, density = mass/volume).
Units and Their Types
- A unit is a constant quantity used to measure other quantities.
- Units must be clearly defined, reproducible, and stable over space and time.
- Base units correspond to base quantities (meter, kilogram, second, etc.).
- Derived units are based on base units (e.g., square meter for area).
Systems of Units
- CGS system: uses centimeter, gram, second.
- MKS system: uses meter, kilogram, second.
- FPS system: uses foot, pound, second.
International System of Units (SI)
- SI is the modern metric system, standardizing measurement globally.
- SI has seven base units: meter (length), kilogram (mass), second (time), mole (amount of substance), kelvin (temperature), ampere (electric current), and candela (luminous intensity).
- SI units are used internationally for scientific communication.
Key Terms & Definitions
- Qualitative observation — observation based on qualities not measurable numerically.
- Quantitative observation — observation based on measurable properties.
- Physical quantity — a measurable property of matter or phenomena.
- Base quantity — independent physical quantity (e.g., length, mass).
- Derived quantity — quantity derived from base quantities.
- Unit — standard quantity used in measurement.
- Base unit — fundamental unit for a base quantity.
- Derived unit — unit derived from base units.
- SI unit system — the standardized international system of measurement.
Action Items / Next Steps
- Review examples of base and derived quantities.
- Memorize the seven SI base units and their corresponding quantities.