1. Chapter 2
Matter and Change

2. Units of Measurement SI Base Units
Length (l) – meter (m)
Mass (m) – kilogram (kg)
Time (t) – second (s)
Temperature (T) – Kelvin (K)
Amount of substance (n) – mole (mol)
Electric Current (I) – ampere (A)
Measurements are agreed upon values representing some quantity
SI Measurements
Scientists agreed on a single system of measurements
Le Systeme International d’Unites (SI)
All other SI Units are derived (they come from combining other units)

3. Derived SI Units Area (A) (m2) l x w Volume (V) (m3) l x w x h
Density (D) (kg/m3) M/V
Molar mass (Mm) (kg/mol) mass / moles
Molar Volume (Vm) (m3/mol) Volume / moles
Energy (E) (J) joule Force x length

4. Conversion Factors Dimensional Analysis
A ratio used to compare one unit of measure to another unit of measure of equal value
1 ft = 12 in 1 kg = 1000 g 1 L = 1000 mL
Dimensional Analysis
A mathematical technique using conversion factors to solve problems

5. Density
Density is a physical property of matter used to help identify a substance
Used in chemistry as an easy way to identify substances
Density = Mass / Volume
D = M / V
Density of water is 1 g/ml
More dense things sink, less dense floats

6. Using Scientific Measurements
Accuracy
Refers to the closeness of measurements to the correct or accepted value
Precision
Refers to the repeatability of the measurements to the same measurement

7. Percent Error A method of showing accuracy in measurements
Negative value says accepted value is greater than experimental
Measured value is sometimes referred to as experimental value
True value is sometimes referred to as accepted value

8. Comparing Measurements
Directly Proportional
If one value goes up the other value also goes up at a constant rate.
Appears as a straight line on a graph
Inversely Proportional
If one value goes up the other value also goes down at a constant rate.
Appears as a curved line (hyperbola) on a graph