1. T. Trimpe 2008 http://sciencespot.net/
Lesson 2: Mass
T. Trimpe

2. Mass is a measure of the quantity of (stuff) matter present
Units of Mass
Mass is a measure of the quantity of (stuff) matter present
Weight is a force that measures the pull by gravity on matter- it changes with location
Mass is constant, regardless of location

3. Weight is the Pull of Gravity
Weight is a measure of the pull of gravity.
Weight is measured with a spring that is compressed or stretched. 3

4. All Matter has Gravity
The elephant has more matter so it has more mass, so it has more gravity.
Even dust is matter so it pulls other dust together by gravity. 4

5. Mass Does Not Change
While on the Earth I will place an object on one side of a balance and an equal amount of water on the other side.
Now I will travel to the moon.
Once on the moon I will repeat the experiment.
Although the moon pulls 1/6th as hard on the object, it also pulls 1/6th as hard on the water, so it still balances.
For this reason scientists prefer to measure matter by it’s mass not weight. 5

6. Units for Measuring Mass
Mass – amount of substance present. Does not change when going to the moon.
Mass is measured on a pan balance.
Weight – related to gravity. Your weight is about 1/3 on the moon and 3X on Jupiter.
As gravity increases your weight increases.
Pull of gravity on jet fighter planes – make your arms and legs very heavy and g-forces increase.
Weight is measured on a scale.
1 kg = lb
Timberlake, Chemistry 7th Edition, page 3

7. Quantities of Mass Giga- Mega- Kilo- base milli- micro- nano- pico-
Earth’s atmosphere
to 2500 km
1018 g
1015 g
1012 g
Ocean liner
Giga-
Mega-
Kilo-
base
milli-
micro-
nano-
pico-
femto-
atomo-
109 g
Indian elephant
106 g
Average human
103 g
1.0 liter of water
100 g
10-3 g
10-6 g
Grain of table salt
10-9 g
10-12 g
10-15 g
10-18 g
Typical protein
10-21 g
Uranium atom
10-24 g
Water molecule
Kelter, Carr, Scott, Chemistry A Wolrd of Choices 1999, page 25

8. Mass 1 kg = 2.2 lbs 1 g = 1 paper clip
1 mg = 10 grains of salt or 2 drops of water.

9. English vs. Metric Units
1 pound = grams
Which is larger?
1. 1 Pound or 100 Grams
2. 1 Kilogram or 1 Pound
3. 1 Ounce or 1000 Milligrams
100 kilogram = 220 pounds
1 ounce of gold = 28,349.5 milligrams

10. Metric Units kg g cg mg
Kilogram Prototype
Mass refers to the amount of matter in an object.
The base unit of mass in the metric system in the kilogram and is represented by kg.
Standard: 1 kilogram is equal to the mass of the International Prototype Kilogram (IPK), a platinum-iridium cylinder kept by the BIPM at Sèvres, France.
Metric Units
1 Kilogram (km) = 1000 Grams (g)
1 Gram (g) = 1000 Milligrams (mg)
Click the image to watch a short video about mass.
Which is larger?
A. 1 kilogram or 1500 grams
B milligrams or 1 gram
C. 12 milligrams or 12 kilograms
D. 4 kilograms or 4500 grams
Kilogram Prototype Image -

11. _______ + ______ + _______ = ________ g
Measuring Mass
We will be using triple-beam balances to find the mass of various objects.
The objects are placed on the scale and then you move the weights on the beams until you get the lines on the right-side of the scale to match up.
Once you have balanced the scale, you add up the amounts on each beam to find the total mass.
What would be the mass of the object measured in the picture?
_______ + ______ + _______ = ________ g
Top Image: Bottom Image:

12. Measuring Mass – Triple-Beam Balance
1st – Place the object to be massed (not weighed) on the scale.
2nd – Slide the large weight to the right until the arm drops below the line. Move the rider back one groove. Make sure it “locks” into place.
3rd – Repeat this process with the top weight. When the arm moves below the line, back it up one groove.
4th – Slide the small weight on the front beam until the lines match up.
5th – Add the amounts on each beam to find the total mass to the nearest tenth of a gram.
Click here to try an online activity.