Name Date Experiment 1, Measurement and Density Chemistry 201, Wright College, Department of Physical Science and Engineering Making measurements in the laboratory involves equipment and instrumentation. Each time you take a measurement, check the graduation of the instrument and then estimate one more place. The total number of significant figures of a measurement includes all of the certain digits (given by the instrument) plus one more estimated digit (you). The density of a pure substance is a physical property of matter and defined as mass per unit volume. The equation to calculate density is density = mass/volume. PRELAB ASSIGNMENT To which decimal place can you read a meter stick? To which decimal place can you read a graduated cylinder? What is the equation to calculate density? What is the equality between atmospheres and millimeters of mercury? PROCEDURE Part A Measurement of a book A meter stick can measure a distance to the hundredth of a centimeter (0.01 cm). The tenth of a centimeter is certain, and then you will estimate the hundredths of a centimeter. 1. Use a meter stick to measure the length and the width of a book in centimeters. Read the ruler to the hundredths of a centimeter (0.01 cm). 2. Calculate the square area (length x width) of the book. Remember to use your rules of significant digits. Show your calculation next to your data. 1
3. Measure the height (thickness) of the book using the small ruler in your bin. Read the ruler to the hundredths of a centimeter (0.01 cm). Calculate the volume (length x width x height) of the book. Remember to use your rules of significant digits. Show your calculation next to your data. Part B Using a graduated cylinder A graduated cylinder measures volume of a liquid. It can be read to the tenth of a milliliter (0.1 ml). Familiarize yourself with the graduation on the graduated cylinder. 1. Fill a Styrofoam cup nearly to the rim with water. 2. You will use your 100.0 ml graduated cylinder to determine how much water is contained in the Styrofoam cup. The Styrofoam cup contains more than the capacity (100.0 ml) of the graduated cylinder, so you will have to pour a portion of the water to the graduated cylinder and take the volume and repeat until all of the water in the Styrofoam cup has been transferred to the graduated cylinder. Remember to read the volume of water in the graduated cylinder to the tenth of a ml (0.1 ml). 3. Record each volume amount on the line in the report sheet. Add all of the volumes together to get the total volume of the water that was in the Styrofoam cup. Remember your significant digits. For example, 89.5 ml + 79.2 ml + 65.4 ml = 234.1 ml 4. Please return the Styrofoam cup to be used again. Part C Density of water 1. Obtain the mass of your small graduated cylinder. The balance will give you the mass to the hundredths of a gram. 2. Add about 12 ml of tap water. Read the graduated cylinder to the 0.1 ml and get the exact volume. Get the mass of the water and the graduated cylinder. Calculate the mass of water. Calculate the density of water. Show your density calculation. 3. Now add more water so that the volume is about 17 ml. Read the graduated cylinder to the 0.1 ml and get the exact volume. Get the mass of the water and the graduated cylinder. Calculate the mass of water. Calculate the density of water. Show your density calculation. 4. Now add more water so that the volume is about 23 ml. Read the graduated cylinder to the 0.1 ml and get the exact volume. Get the mass of the water and the graduated 2
cylinder. Calculate the mass of water. Calculate the density of water. Show your calculation next to your data. 5. Make a graph of mass (y axis) vs. volume (x axis) in the graph provided. Draw a best fit line through the 3 points. Part D Identification of an unknown solid 1. Choose an unknown metal and record its unknown number. 2. Obtain the mass of the metal. 3. Place about 15 ml of water in your small graduated cylinder and record the exact volume to the tenth (0.1) of a ml. Tilt the graduated cylinder and slide the metal in. 4. Read the exact volume of metal in the water. Calculate the volume of the metal. 5. Calculate the density of the metal and use the table below to identify the metal. Show your calculation next to your data. metal Density (g/cm 3 or g/ml) aluminum 2.702 copper 8.92 steel 7.083 brass 8.44 lead 11.36 titanium 4.43 Part E Pressure 1. Obtain the atmospheric pressure by reading the lab s barometer in hectopascals (hpa) and millimeters of mercury (mmhg). Both instruments can be read to the 0.1 of the unit. Convert both of these units to atmospheres (atm) where 1 hpa = 0.0009869 atm and 1 atm = 760.0 mmhg. Remember significant digits. Show your calculations next to your data. Part F Temperature 1. Obtain the ambient temperature of the laboratory by taking the temperature in degrees Fahrenheit. Read the thermometer to the tenth of a degree (0.1 o F). Record this temperature in the report sheet. 3
2. Convert this temperature to degrees Celsius, o C = ( o F 32) x 5/9. Record this temperature in the report sheet. 3. Obtain the ambient temperature of the laboratory by taking the temperature in degrees Celsius. Read the thermometer to the tenth of a degree (0.1 o C). Record this temperature in the report sheet. 4. Convert this temperature to Kelvin, K = o C + 273.15. Remember significant digits. Show your calculation next to your data. 4
Name REPORT SHEET Part A Measurement of a book Width of book cm Length of book cm Area of book cm 2 Height of book cm Volume of book cm 3 Part B Using a graduated cylinder Portions of water from Styrofoam cup: Total volume of water in Styrofoam cup ml Part C Density of water Mass of graduated cylinder g Exact volume of about 12 ml of water ml Mass of graduated cylinder and water (12 ml) g Mass of water (12 ml) g Density of water (12 ml) g/ml Exact volume of about 17 ml of water ml Mass of graduated cylinder and water (17 ml) g Mass of water (17 ml) g 5
Density of water (17 ml) g/ml Exact volume of about 23 ml of water ml Mass of graduated cylinder and water (23 ml) g Mass of water (23 ml) g Density of water (23 ml) g/ml What can you say about the density of water? Part D Identification of an unknown solid Unknown # Mass of metal g Volume of water in graduated cylinder ml Volume of metal and water in graduated cylinder ml Volume of metal ml 6
Density of metal g/ml Identity of metal Part E Pressure Atmospheric pressure hpa = atm Atmospheric pressure mmhg = atm Part F Temperature Temperature from thermometer o F Calculated temperature o C Temperature from thermometer o C Calculated temperature K 7
QUESTIONS (Show your work) 1. How many milliseconds are in 18 days? 2. The mass of a single gold atom is 3.27x10-22 g. What is this mass in pounds? 1 kg = 2.205 pounds 3. Convert 25 miles/hour to km/s. 1 km = 0.6214 miles Updated 1-31-17 MV 8