Theories and ideas are tested by measurement
Measurements are usually quantitative – have numbers
Science is built on a foundation of mathematics.
In recording measurements, it is necessary to understand
1. SIGNIFICANCE of numbers
2. importance of UNITS.

1. Understand importance of units in measurement
2.
Identify common “metric” units
3. Apply common metric prefixes
4. Use simple unit conversions
5. Recognize the scales of temperature
6. Perform conversions between temperature scales

English System - what the United States uses today derived from the 'Kings" feet
(Old England). Also known as the United
States Customary System (USCS)
Units
1 foot (“big feet")
1 inch (knuckle)
1 yard (King Henry I - nose to thumb)

The creation of the decimal Metric
System at the time of the French
Revolution and the creation of two platinum standards representing the meter and the kilogram was the first step in the development of the present International System of Units.
Science has adopted the S.I. When we say “metric” we mean S.I.

Not only inexperienced chemistry students can be confused by units
Whoops!

mega- (M) 1,000,000 kilo- (k) 1,000
10 6
10 3 deci- (d) 1/10 centi- (c) 1/100
10 -1
10 -2 milli- (m) 1/1,000 micro- (

) 1/1,000,000
10
10
-3
-6 nano- (n) 1/1,000,000,000 10 -9

Physical property Name of unit Symbol
Length meter m
Mass kilogram kg
Time
Electrical current second ampere s
A
Temperature
Luminous intensity
Kelvin candela
Amount of substance mole
K
Cd mol

Length is a fundamental unit. In the metric system, the meter is a the standard unit for measuring length. It is a little longer than a yard.
The standard unit of metric length is kept in
Paris. It is equal to 39.37 inches. Since the meter is equal to 100 centimeters (cm), then 1 inch is equal to 2.54 cm.
Comparisons: centimeter - width of your fingernail kilometer - 0.60 miles millimeter - thickness of a dime

Mass is a fundamental unit; it is a measure of the quantity of matter present. Although we typically use the words mass and weight interchangeably in normal conversation, mass and weight actually have different meanings. Weight includes the effect of gravity on mass. In a space capsule, your weight would be zero (absence of gravity) but your mass would be the same value as it was on earth.
The standard unit of mass is the kilogram (kg).
Conversions factors:
1 pound = 454 g
2.2 pounds (lb) = 1 kilogram (kg)
1 gram (g) = 1000 milligrams (mg) or 1 mg = 0.001 g
1 kilogram (kg) = 1000 grams (g) or 1 g = 0.001 kg

– volume is a derived unit (using length units). It is a measure of space. In simple terms, it is a measure of three
(3) length units in three dimensions (breadth, length and width). The standard unit of measurement is the meter cubed
(m 3 ) or the centimeter cubed (cm 3 ).
In chemistry, volume is typically measured for a liquid. The standard unit of measurement for a liquid is the liter (L). The liter is similar to a quart in the English system.
Conversion factors:
1 liter (L) = 1.06 quarts (qt)
1 quart (qt) = 0.946 liters (L)
1 liter (L) = 1000 milliliters (ml) or
1 milliliter (ml) = 0.001 liter (L)
1 milliliter (ml) = 20 drops
At room temperature, 1 milliliter (ml) of water = 1 cm 3 . (or 1 CC)

A fundamental unit. There are three(3) temperature scales
BP
H20
(1) Fahrenheit (F) 212 °
(2) Celsius (centigrade) (C) 100 °
FP
H2O
32 °
0 °
Difference
180
100
°
(3) Kelvin (K) 373 273 100
°
Conversion:
Kelvin to Celsius (K -> C) C = K - 273
Celsius to Kelvin (C -> K) K = C + 273
Celsius to Fahrenheit (C -> F) i multiply C x 9/5 ii Add C x 9/5 + 32
Fahrenheit to Celsius (F -> C) i add F - 32 ii multiply (F - 32) x 5/9

Derived units can be resolved into combinations of fundamental units
Area and volume involve only the units of length
Most involve combinations of different units

It is important to keep track of the dimensions in derived units.
All the more when making conversions:
1 cm = 10 mm
1 cm 2 = 100 mm 2
1 cm 3 = 1,000 mm 3

Making conversions between different units is very important
Always keep track of the units
Make use of unit factors
There are 1000 mg in 1 g (conversion factor)
1000 mg/1 g = 1; 1 g/1000 mg = 1 (unit factors)
There are two unit factors for any conversion

How many grams are there in 2680 mg of sucrose?
We know there are 1 000 mg in 1 g
1 g/1000 mg = 1 (unit factor)
? g = amount in mg x unit factor
? g = 2680 mg x 1 g /1000 mg = 2.680 g
Unit factor has value of 1 – no change in value
Application of unit factor causes old units to cancel
Never forget to show units of any measurement – unless it is a unit-less quantity

Mass divided by volume
Units are: g/cm 3 (solid) g/mL (liquid) g/m 3 (gas)

In most cases, the density of a substance decreases with temperature. (Why is that?)
Water provides a critical exception to the rule