BackMetric System, Units, and Temperature Scales in General Chemistry
Study Guide - Smart Notes
Tailored notes based on your materials, expanded with key definitions, examples, and context.
Metric System and Dimensional Analysis
Base Units in the Metric System
The metric system is a standardized system of measurement used in science, including chemistry. It is based on a set of fundamental units for different physical quantities.
Mass: gram (g)
Length: meter (m)
Time: second (s)
Temperature: degrees Celsius (°C) or Kelvin (K)
Amount of substance: mole (mol)
Volume: cubic centimeter (cm3 or cc) or liter (L)
Physical Quantities and SI Units
The International System of Units (SI) defines standard units for various physical quantities. The table below summarizes some key quantities and their SI units:
Physical Quantity | Name of Unit | Abbreviation |
|---|---|---|
Length | Meter | m |
Mass | Gram | g |
Time | Second | s |
Temperature | Kelvin | K |
Amount of substance | Mole | mol |
Electric current | Ampere | A |
Luminous intensity | Candela | cd |
Metric Prefixes
Metric prefixes are used to indicate multiples or fractions of base units. They are essential for expressing very large or very small quantities conveniently.
Prefix | Abbreviation | Exponential Notation | Numerical Value | Example |
|---|---|---|---|---|
tera | T | 1012 | 1,000,000,000,000 | 1 Tm = 1012 m |
giga | G | 109 | 1,000,000,000 | 1 Gm = 109 m |
mega | M | 106 | 1,000,000 | 1 Mm = 106 m |
kilo | k | 103 | 1,000 | 1 km = 103 m |
deci | d | 10-1 | 0.1 | 1 dm = 0.1 m |
centi | c | 10-2 | 0.01 | 1 cm = 0.01 m |
milli | m | 10-3 | 0.001 | 1 mm = 0.001 m |
micro | μ | 10-6 | 0.000001 | 1 μm = 10-6 m |
nano | n | 10-9 | 0.000000001 | 1 nm = 10-9 m |
pico | p | 10-12 | 0.000000000001 | 1 pm = 10-12 m |
Temperature Scales
Celsius Scale
The Celsius scale is commonly used in chemistry for measuring temperature. It is based on the properties of water:
0°C: Freezing point of water
100°C: Boiling point of water
Widely used in laboratory settings
Kelvin Scale
The Kelvin scale is the SI unit for temperature and is based on absolute zero, the theoretical lowest possible temperature. It is used in scientific calculations because it does not allow negative values.
Based on: Absolute zero (0 K), the point at which molecular motion stops
No negative values: All temperatures are positive
Conversion from Celsius:
Formula:
Energy and Derived Units
Density
Density is a physical property defined as mass per unit volume. It is commonly used to characterize substances in chemistry.
Formula:
D: Density
m: Mass
V: Volume
Example: The density of water at 4°C is approximately 1.00 g/cm3.
Summary Table: Common SI Prefixes
Prefix | Abbreviation | Factor | Exponential Notation |
|---|---|---|---|
kilo | k | 1,000 | 103 |
centi | c | 0.01 | 10-2 |
milli | m | 0.001 | 10-3 |
micro | μ | 0.000001 | 10-6 |
nano | n | 0.000000001 | 10-9 |
Additional info:
Energy units such as the joule (J) are also commonly used in chemistry, though not explicitly listed in the notes.
Dimensional analysis is a method used to convert between units using conversion factors, ensuring that calculations are consistent and correct.
