1. Scientific Measurements Supplemental instruction Designed by Pyeongsug Kim ©2010 sibio@att.netsibio@att.net Picture from http://wps.prenhall.com/wps/media/objects/165/169061/blb9ch0104.htmlhttp://wps.prenhall.com/wps/media/objects/165/169061/blb9ch0104.html Fall 2010 For Mr. Yee’s CHEM 1A Class Updated: Friday, July 11, 2010

2. Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.comObservations Qualitative observationQualitative observation -using all 5 senses -Color, Texture, … Picture from http://www.eligr.com/html-color-codes/ http://blog.tradetang.com/the-most-effective-way-to-lose-weight-only-for-menhttp://www.eligr.com/html-color-codes/http://blog.tradetang.com/the-most-effective-way-to-lose-weight-only-for-men Quantitative observationQuantitative observation -an observation using data, numbers, and graphs -Measurement attached a number. (Volume, Length, mass, density….)

3. Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com Scientific figures -The meaningful digits in a measured or calculated quantity. Picture from http://www.zazzle.com/happy_mole_day_avogadros_number_tshirt-235997985923855952http://www.zazzle.com/happy_mole_day_avogadros_number_tshirt-235997985923855952 2 6.02 X 10 23 Scientific notation # of scientific figure : _____ 3 0 0.000122300 # of scientific figure : _____ 6 3 0.0001223 # of scientific figure : _____ 4 0.000122300 = 1. 22300 X 10 -4 0.000122300 =1. 223 X 10 -4 122,300,000 =1. 223 X 10 8 1 12.011 # of scientific figure : _____ 5 Uncertainty: _________ ±0.01 Uncertainty: _________ ±0.000000001 Uncertainty: _________ ±0.0000001 Uncertainty: _________ ±0.001

4. A mass of 13.20 g indicates an absolute uncertainty of ______. 0.01 g A mass measured to 13.2 g is said to have an absolute uncertainty of ____ and is said to have been measured to the nearest ____. 0.1 g Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com Round 1.2459 to 3 significant figures. _____ 1.25 8.16 m X 5.1355 = ______m 41.9 * Choose lowest scientific significant 0.0154 kg ÷ 88.3 ml = 0.000174405436 kg/ml = ___________ 1.74 X 10 -4

5. Reading Graduated Measuring Devices Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com Graduated -marked with equally spaced lines corresponding to incremental values of the quantity measured. 100-mL graduated cylinder can measure upto 100 mL marked with large lines every 10 mL smaller lines every 1mL Picture from http://dl.clackamas.cc.or.us/ch104-01b/volume_meas.htmhttp://dl.clackamas.cc.or.us/ch104-01b/volume_meas.htm 10-mL graduated cylinder can measure upto 10 mL marked with large lines every 1 mL smaller lines every 0.1 or 0.2 mL

6. Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com How to Measure Volume What is the volume of the liquid in the graduated cylinder? What type of cylinder is below? 43 ± 1 ml Picture from http://ritter.tea.state.tx.us/student.assessment/resources/online/2006/grade8/science/8science.htmhttp://ritter.tea.state.tx.us/student.assessment/resources/online/2006/grade8/science/8science.htm 52.7 ± 0.5 ml Uncertainty = ±1 Uncertainty = ±0.5 100 ml graduated cylinder Uncertainty = ±0.05 5.88 ± 0.05 ml 10 ml graduated cylinder

7. Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com Accuracy vs. Precision AccuracyAccuracy -How close a measured value (average value) is to the actual (true) value. - % error from actual value. PrecisionPrecision -How close the measured values are to each other. - % difference from average value. Low Accuracy High Precision High Accuracy Low Precision High Accuracy High Precision Picture from http://www.mathsisfun.com/accuracy-precision.htmlhttp://www.mathsisfun.com/accuracy-precision.html % error = -------------------------------- X 100 % Experimental value - Actual value Actual value

8. Compare the results of two guys: Which guy’s results are more precise? Give a reasons. Because the average value 2.001g is closest to the true value, 2.000g. Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com Three guys are asked to determine the mass of a piece of copper wire with two weighings. The true mass of the wire is 2.000g. 1.964 g 1.972 g Picture from http://www.cartoonlogodesigns.com/Smiley%20Cartoon%20Logos.htmhttp://www.cartoonlogodesigns.com/Smiley%20Cartoon%20Logos.htm 1.972 g 1.968 g 2.000 g 2.002 g Find average value in each guys. 1.971 g1.970 g2.001 g Because 1.972g and 1.968g deviate less from 1.970g than 1.964g and 1.972g from 1.971g. Which guy’s results are most accurate? Give a reasons.

9. - the amount of mass in a unit volume of the substance.Density Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com Density = -------------- = g / ml or g / cm 3 Volume Mass MaterialDensity Rubbing Alcohol.79 Lamp Oil.80 BabyBaby Oil.83 Vegetable Oil.92 Ice Cube.92 Water1.00 Milk1.03 Dawn Dish Soap1.06 Light Corn Syrup1.33 Maple Syrup1.37 Honey1.42 Low density High density Picture from http://www.stevespanglerscience.com/experiment/seven-layer-density-columnhttp://www.stevespanglerscience.com/experiment/seven-layer-density-column

10. Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com Picture from http://blog.teachersource.com/category/high-school-level/page/3/http://blog.teachersource.com/category/high-school-level/page/3/ Slope = Mass(g) / Volume(cc, ml, cm 3 ) = Density !

11. = ? Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com Lower volume Same mass Higher density Higher volume Same mass Lower density Density = -------------- = g / ml or g / cm 3 Volume Mass

12. Finding the Volume of an regular shaped object An object that can be measured by a ruler Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com Picture from http://library.thinkquest.org/26342/sections/math_lessons/lessons/volume_of_cube.htmhttp://library.thinkquest.org/26342/sections/math_lessons/lessons/volume_of_cube.htm

13. Finding the Volume of an irregular shaped object - An object that can not be measured by a ruler - the water displacement method Picture from http://www.gstboces.org/homework/secure/attachments/01170706104237.dochttp://www.gstboces.org/homework/secure/attachments/01170706104237.doc Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com the volume of the object (V object ) = V displaced water after the object is placed in it + V water  What is the volume of object? 2 ml

14. Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com a. Calculate the density of mercury if 1.00 x 10 2 g occupies a volume of 7.36 cm 3. Density = Mass / Volume = ------------------ = 1.00 x 10 2 g 7.36 cm 3 13.6 g/cm 3 b. Calculate the volume of 65.0 g of the liquid methanol (wood alcohol) if its density is 0.791 g/mL. Volume = Mass / Density = ------------------ = 65.0 g 0.791 g/mL 82.2 ml c. What is the mass in grams of a cube of gold ( density 19.32 g/cm 3 ) if the length of the cube is 2.00 cm. Mass = Volume X Density Volume of Cube = 2.00 cm X 2.00 cm X 2.00 cm = 8.00 cm 3 8.00 cm 3 X 19.32 g/ cm 3

15. Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com Fall 2009 Quiz #2 (in class) 50 ml of H 2 O at 2l o C (true Density = 0.998 g/ml ) is pour into a beaker of mass 55.23g. The mass of the beaker & water is 63.39g. Calculate the density of H 2 O, Calculate the % error. Comment on accuracy and precision. Picture from http://www.chemistryland.com/CHM107Lab/Lab5/Filters/Lab5Exp2filters.htmlhttp://www.chemistryland.com/CHM107Lab/Lab5/Filters/Lab5Exp2filters.html

16. Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com 2. (6 points) You are asked to review the following mass-volume data: Table 1. Mass and Volume of Water at 25oC You see that the experimenter graphed volume of water on the y-axis and mass of water on the x-axis using the Graphical Analysis software. A linear fit of the data points gives a slope of 1.02 and a correlation of 0.998. You use Graphical Analysis to determine the density of water from the three data points to be 0.962 g/ml. Spring 2005 Quiz 1 RunMass of Water, gVolume of Water, ml 19.8710.0 220.5520.0 329.1130.0 a. Based on the volume of water in Table 1, which volume measuring device did the experimenter use: a 10 ml graduated cylinder (uncertainty =  0.05 ml), a 100 ml graduated cylinder (uncertainty =  0.5 ml), or a 100 ml beaker (uncertainty =  5 ml)? Give reasons. b. Explain why you got a different density than the experimenter. Who got the correct density? Give reasons. Picture from http://teenormous.com/t-shirts/80stees-Bunsen-and-Beaker-t-shirt-176165http://teenormous.com/t-shirts/80stees-Bunsen-and-Beaker-t-shirt-176165

17. 3. (6 points) The following is a label taken from a 1.5 liter (50.7 oz.) bottle of Castle Rock Spring Water. Nutrition Facts: Serving Size 8 oz. (240 ml)ANALYSIS (mg/liter) About 6 servings per containerCalcium.......................... 10 Amount per servingMagnesium...................... 5 Calories 0Bicarbonates.................. 65 Total Fat 0 gPotassium........................ 2 Sodium 0 mgChloride........................... 2 Total Carb. 0 gNitrate........................... <1 Protein 0 gTDS Approximately 80 (TDS stands for Total Dissolved Solids) a. Compare the analysis of calcium to bicarbonates on the label. Which substance has the larger uncertainty in the reported value? Provide reasoning to support your answer. b. The label states that the bottle contains 1.5 L of water. How many grams of magnesium are present in this bottle of water? c. The six substances (ignore TDS) in the Analysis section on the label exist in water as ions. You boil off all of the water and see a solid at the bottom of the container. Give the name and chemical formula of one compound that this solid could be. Identify this compound as molecular or ionic. Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com Fall 2001 Quiz 1 & Spring 2005 Quiz 1 Picture from http://www.privatespringwater.com/about.htmlhttp://www.privatespringwater.com/about.html

18. You and your lab partner are measuring the properties of a colorless liquid. The following data were taken with a single-pan analytical balance for mass and a graduated cylinder with graduations every 1 ml for volume: Runmass of liquid, gvolume of liquid, ml 14.9675.00 210.00210.00 314.89615.00 419.97820.00 a. Are the significant figures in the volume data reported correctly? Give reasons. b. Using Graphical Analysis, plot a graph of mass of liquid (y-axis) vs. volume of liquid (x-axis). c. What property does the slope of the line on this graph represent? d. What is the identity of this liquid? e. The true value for this property is 0.988 (units). What are the units of this property? f. From the true value from part (d), does the above data show a random error or systematic error? Give reasons. Spring 2004 Final exam Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com Picture from http://www.johnnygoodtimes.com/archives/2004_09.shtmlhttp://www.johnnygoodtimes.com/archives/2004_09.shtml

19. You are measuring the volume of a solid by two methods: (1) ruler measurement of length, width, and height, and (2) liquid displacement. You obtain the following data: Run Volume by ruler, cm3Volume by liquid displacement, ml 16.87.0 27.56.8 36.06.8 47.17.2 Calculations are not required to answer these questions. (1 cm3 = 1 ml) a. Based on the above data, which method shows the greater precision? Give reasons to support your answer. b. Based on the above data, which method shows the greater accuracy? Give reasons. c. Based on the volume by ruler data, do you think the solid has a regular shape, e.g., a cube, or an irregular shape? Give reasons. d. Based on the volume by liquid displacement data, what are the graduations on the graduated cylinder, e.g., 10 ml, 5 ml, 1 ml, 0.1 ml, etc.? Give reasons. Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com Spring 2004 Final exam Picture from http://www.johnnygoodtimes.com/archives/2004_09.shtmlhttp://www.johnnygoodtimes.com/archives/2004_09.shtml

20. Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com 3. (10 points) You find a blue rock and a green rock in your backyard. Each rock is approximately the same mass. The blue rock has a larger volume than the green rock. a. Which rock is more dense? Give reasons. b. You take each rock and break them into different sized pieces. For each piece, you measure the mass and volume. You graph the mass of each rock (y-axis) vs. the volume of each rock (x-axis). On the graph below, identify which line represents the blue rock and which line represents the green rock. Give reasons for your choice. | mass, g| | |_________________________ volume, ml c. Describe how you could use the results of your experiment to identify the type of rock. Fall 2002, Quiz1 Picture from http://www.ccsr.com/160602.ihtmlhttp://www.ccsr.com/160602.ihtml

21. 3. (13 points) An interviewer for your first job as a lab technician asks you to describe how you would calculate the density of a colorless liquid from the following data: RunVolume, mlMass, gDensity, g/ml 110.007.9452 220.0016.0025 330.0023.8276 440.0036.2584 550.0039.5899 Average Density = a. Based on the significant figures shown in the Volume column, which volume measuring device do you think was used? Give reasons. b. For each run, calculate the density of the liquid. Then, calculate the average density. (Extra credit: 1 point. Use an Excel spreadsheet to calculate density. Print your spreadsheet and turn it in.) Comment on the precision of these 5 runs. (See the Chem 1A Lab Manual, p. 12 and Moore, “The Chemical World”, p. A-6 for precision.) c. Using the Graphical Analysis software, plot mass vs. volume. Use the mouse to draw a box around all of the data points on the graph. Then, go to the Analyze pull down menu and select Regression. Record the slope (M), intercept (B), and correlation coefficient (COR). Print out your graph and turn it in. Calculate the density of the liquid from your graph. Comment on the precision of these data. d. Compare the data in the table and in your graph. Are all the data points “good” or should one or more data points be discarded? If a data point should be discarded, identify the data point and explain why this data point should be discarded. e. Compare the average density you calculated in part b to the density from the graph in part c. Which density do you “trust”? Give reasons. f. The colorless liquid is either water, ethanol, or hexane. Look up the density of each substance at 25 o C. Cite the reference where you found this information. Based on the density data, what is the identity of the liquid? Calculate a % error. Show your calculations. Designed by Pyeongsug Kim, ©2010 www.science-i.comwww.science-i.com Fall 2001 Quiz 1 Picture from http://science.nayland.school.nz/SimonPa/index.htmhttp://science.nayland.school.nz/SimonPa/index.htm