1. Unit 7 - Calculate Derived Units Students will learn to differentiate between base units and derived units. In addition, students will be able to perform mathematical operations to determine the density of an object.

2. Basic units Measure distance in METERS (m, cm, km). Measure volume (most of the time) in LITERS. Measure time in SECONDS (s, ms). Measure mass in GRAMS (mg, g, kg). In this class, we will consider a unit “BASIC” if we can measure it directly with one of our available instruments like a ruler or stopwatch.

3. Mass & Volume In chemistry, two rule are true for all matter: #1. Composed of atoms (has mass) #2. Takes up space (has volume) In your notes, take a second to describe what MASS and VOLUME mean in your own words.

4. Derived units In the lab, some measurements cannot be obtained directly. Instruments that can measure these values may be too expensive or impractical to use. Therefore, we're going to have to learn how to figure these things out ourselves...

5. Derived units Derived units are found by MULTIPLYING and/or DIVIDING basic units together. In other words, you have to solve a math problem to figure them out. Ex: cm x cm x cm = cm 3 (volume of a solid) Ex: m ÷ s = m/s (speed)

6. Checkpoint Which of these things is a DERIVED UNIT? a. Temperature in degrees Celsius ( ° C) b. Distance traveled in meters (m) c. Square footage of a house (ft 2 )

7. Derived Measurement: Density There's only one thing I want you to learn how to derive today. Its called DENSITY. “The ratio of an object's mass to its volume” - that's what the textbook says density means.

8. Figuring out density Step #1: Determine the object's mass using a scale or triple-beam balance. Mass is measured in GRAMS. Step #2: Determine the volume using a graduated cylinder or by doing L x W x H. Volume is measured in MILLILITERS or CM 3. Step #3: Compare the object's mass to how much space its taking up using DIVISION. This tells you the density.

9. Example problems Lets do these problems together in your notes... DON'T FORGET ABOUT SIGNIFICANT FIGURES!! Recycled aluminum cans are smashed into cubes that are 10.cm 3 with a mass of 27g. What is the density? What is the density of approximately 50mL of water with a mass of 49.2 grams?

10. Checkpoint The mass of a metal block is 120. grams. The size of the block is 6.00 cm 3. What is the density of the metal block? a. 20 g b. 20.0 cm 3 c. 20 g/cm 3 d. 20.0 g/cm 3