1. VERBAL INTERPRETATION OF RATIOS

2. This rock has a measured mass of 340 g and a volume of 120 cm3

3. How do you interpret the number 340 120?
Tell what it means using the simplest possible words.
If the answer is “density”, point out that a technical term or name is not an interpretation.
Mass g
Volume 120 cm3

4. Let’s look at a different scenario
Suppose we go to a store and find a box that contains 3 kg of material that costs $5.00.

5. What is the meaning of the number 5.00 3?
How many dollars we pay for one kilogram.
Cost $ Mass 3 kg

6. Another example
A car drives 300 miles using 10 gallons of gasoline.

7. What is the meaning of the number 300 10?
How many miles the car drives using one gallon of gasoline, or 30 miles per gallon.
Per means for each and indicates that division has been used in computing the number. Thus, 30 miles per gallon means 30 miles for each gallon.
Miles Gallons 10

8. Interpreting Ratios
If something has two quantities, A and B, associated with it, then the ratio A B
___
means, how many units of A (in the numerator) are associated with one unit of B (in the denominator).

9. How much one gets for one dollar.
Back to our store example. Now consider the number _3_ Does this number have an interpretation?
How much one gets for one dollar.
Cost $ Mass 3 kg

10. Density, mass per unit volume
What does = 2.8 g/cm3 mean?
The quantity 2.8 is the number of grams in one cubic centimeter.

11. Mass, Volume and Density
Mass, volume and density are all properties of matter Mass and volume tell us something about a specific object Density contains information about objects made of the same material Under the same conditions, all objects made of the same material have the same density This is not true for mass and volume