WARMUP (5 min): Yes, we will do these problems together in class today. Try them now though! = x 3. (yes, #3) The density of oxygen gas is g/ml. What is the volume of grams of oxygen gas? Try this problem using the equation density = mass/volume

Density and Graphing Refer to ‘graphing handout’ and ‘density and graphing’ lecture notes. Take notes on these as well as your own note paper. HW: watch Happy Gilmore sometime during the next 2 weeks

Algebra Review = x 7.7x = 21(5.8)7.7 x = x = 16

What is density?  mass per unit volume  amount of matter that is packed into a certain space  unique for a material; stays constant if temperature does not change  units: g/ml, g/cm 3, kg/L, etc

12.0 cm mg 24 cm 3 14 mg 2. Which box has the greatest density? Prove it mathematically. The green box! It’s the ratio of mass to volume that matters, not how big or small the mass and volume values are. D = m/v = 9.0 mg/12.0 cm 3 = 0.75 mg/cm 3 D = m/v = 14 mg/24 cm 3 = 0.58 mg/cm 3

3. The density of oxygen gas is g/mL. What is the volume of grams of oxygen gas? m = dvv = m/dd = m/v v = (0.070 g)/( g/ml) = 53 ml O 2 4. The density of chloroform is g/ml. What is the mass of 6.2 x 10 4 ml chloroform? m = dvv = m/dd = m/v m = (1.492 g/ml)(6.2 x 10 4 ml) = 9.3 x 10 4 g chloroform

5. An unknown material has a mass of 0.44 grams and a volume of 0.5 ml at 20°C. a. What is the identity of this material? b. What if the volume was actually 0.56 ml, but the student recorded just 0.5 ml? SubstanceDensity (g/ml) Chloroform1.492 Benzene0.880 Isopropanol0.785 Toluene0.867 Ethanol0.789 D = 0.44g/0.5ml = 0.88 = 0.9 g/ml Benzene! D = 0.44g/0.56ml = = 0.79 g/ml Isopropanol? Ethanol?

5. An unknown material has a mass of 0.44 grams and a volume of 0.5 ml at 20°C. c. Have we made measurements that are precise enough to draw conclusions about substance identity based on density? Explain. d. Using the accepted value for density, what would be the volume of 90.1 grams of ethanol? SubstanceDensity (g/ml) Chloroform1.492 Benzene0.880 Isopropanol0.785 Toluene0.867 Ethanol0.789

Buoyancy: the ability of an object to float in liquid *based on densities of the liquid and the object 6. The density values of several objects are listed below. With partner, discuss if each of these items will float or sink in water (1.0 g/ml). Why? marble = 10.2 g/ml wooden cork = 0.15 g/ml, full soda = 1.08 g/ml brick = 6.7 g/ml inflated beach ball = g/ml

7. If you mix chloroform, toluene and water together. which layer will be on the top? The middle? The bottom? Discuss with neighbor SubstanceDensity (g/ml) Chloroform1.492 Benzene0.880 Isopropanol0.785 Toluene0.867 Ethanol0.789 water toluene chloroform

8. A 6.78g metal piece is placed in a graduated cylinder filled with ml water. The water rises to ml. What is the density of this metal? ml ml D = m/v = 6.78g/ 8.69 ml V metal = = 8.69 ml D = g/ml Wait a second…is this possible? What could have happened?

9. Let’s say you recorded the volume of a necklace as 12 ml and the mass as 86 grams. Another group recorded the volume if the same necklace as 10.9 ml, and the mass as 85.9 g. a.What would the density results be for each group? b.What metal does each group think the necklace is made of? c.Which group made a mistake? How? Why? MetalAtomic Number Density (g/cm 3 ) Zn Mg Sn Hg Si Bi Pb Au Fe Co Al Cu

Time (seconds) Distance (meters) The data table shows the relationship between the time a person spends running and the distance he/she travels. Graphing the data will show us the relationship and allow us to make other predictions. Graphing Guidelines Neat using pencil and sheet of graph paper, or Microsoft Excel (later). Utilize all paper space! 1. Title 2. Labeled X (independent variable) and Y (dependent variable) axis, including units 3. Accurately scaled X and Y axis (see your handout for a very specific yet weird example of how Ms Jonson does this). Do NOT just label the x and y axis with numbers from the data points! 4. Carefully plotted data points with a best fit line or curve (unless otherwise specified). DO NOT CONNECT THE DOTS!

When the variable on the X axis increases, does the other variable increase, decrease, or stay the same? Is the relationship between the variables linear (straight line) or exponential (curved)? *Time and distance have a direct, linear relationship. As time increases, distance increases. How long would it take for this person to run 412 m? 72 seconds“extrapolation”

10. The following set of data shows the time a student spent practicing problems to study for a chemistry test, and his/her score on each test. a. Graph the data according to the guidelines. b. Describe the trend shown by the graph. c. If the student studied for 3.4 hours, what grade would he/she earn on the next test? d. What measurement errors are present? Study Time (hours) Grade (%) %

MetalAtomic Number (amu) Density (g/cm 3 ) Zn Mg Sn Hg Si Bi Pb Au Fe Co Al Cu The densities of various metals were measured and their values are listed to the left. a. Graph the data according to the guidelines. b. Describe the trend shown by the graph. c. Based on the trend, predict the approximate density of the element chromium. 5.5 g/cm 3 Ms Jonson….show students how to do superscripts and subscripts like in cm 3 and Ca 3 (PO 4 ) 3