Chemistry - An Introduction to General, Organic, and Biological Chemistry: Chemistry and Measurements
Chemistry and Measurements
Units of Measurement
- Scientists employ the metric system and its modification, the International System of Units (SI), as a global standard.
- The International System of Units (SI) is the official measurement system for:
- Length
- Volume
- Mass
- Temperature
- Time
Metric and SI Units
- Table 2.1 summarizes units of measurement and their abbreviations.
| Measurement | Metric | SI | U.S. |
|---|
| Volume | liter (L) | cubic meter | quart (qt) |
| Length | meter (m) | meter (m) | mile (mi), inch (in) |
| Mass | gram (g) | kilogram (kg) | pound (lb), ounce (oz) |
| Temperature | degree Celsius (°C) | kelvin (K) | degree Fahrenheit (°F) |
| Time | second (s) | second (s) | second (s) |
Volume
- Volume: The space occupied by a substance.
- SI unit: cubic meter.
- Chemists commonly use liters (L) and milliliters (mL).
- Graduated cylinders: Tool for measuring small volumes.
- Useful relationships:
- 1 L = 1000 mL
- 1 L = 1.06 qt
- 946 mL = 1 qt
Length
- Length: measured in meters (m) in both metric and SI systems.
- Chemists often use centimeters (cm).
- Useful relationships:
- 1 m = 100 cm
- 1 m = 39.4 in.
- 1 m = 1.09 yd
- 2.54 cm = 1 in.
Mass
- Mass: A measure of the quantity of material in an object.
- Measured using an electronic balance.
- SI unit: kilogram (kg).
- Chemists often measure mass in grams (g).
- Useful relationships:
- 1 kg = 1000 g
- 1 kg = 2.20 lb
- 454 g = 1 lb
Temperature
- Temperature: Measure of how hot or cold an object feels.
- Measured on the Celsius scale.
- SI unit: Kelvin (K).
- Water freezes at 0 °C and boils at 100 °C.
- The Kelvin scale starts at absolute zero, 0 K.
Time
- Time is based on an atomic clock and is measured in seconds (s) in both the metric and SI systems.
- Stopwatch: used to measure time.