Define the term “density” using your own words.How would you use a demonstration to compare the densities oDetermine the volume of the following. Pay attention to unitExperimentData from the volumetric pipetteI. D. number of the analytical balance _____________Trial 4Trial 4Accuracy = observed value - true valueIntroduction to Natural Science (2006/07) Fall 2006 Quarter Chemistry Lab I: “Chemical Foundations” Prepared by: Dr. Dharshi Bopegedera A good website for density of elements is: www.science.co.il/PT elements.asp?s=Density All liquids are alcohols. Look up the CRC under “organic liquids”1Pre-Lab Assignment Complete the Pre-lab before coming to lab Part I: Exploring physical and chemical properties Define the following terms using your own words (you can read the chemistry text, but use your own words). • Chemical property (give 2 examples) • Physical property (give 2 examples) PART 2: Density Measurements 1. Define the term “density” using your own words. 2. How would you use a demonstration to compare the densities of water, oil, wood and iron nails to a sixth grade student. Describe your demonstration in detail and draw a labeled diagram of your experiment. 3. Determine the volume of the following. Pay attention to units. • A cube that has a length of 12.5 cm • A sphere with a radius of 2.34 cm 4. Volumes of solids are often determined by displacement, specially when they are irregular in shape. For this purpose you must first find a liquid in which the solid of interest in not soluble. Then add a specific volume of the liquid to a graduated cylinder (or other graduated device). Add the solid to the liquid in the cylinder. Measure the combined volume of the liquid and the submerged solid. The difference between these two volumes is the volume of the solid. It is important that the liquid you select have a density lower than that of the solid so that the solid will not float on the liquid. A metal block has a mass of 12.5 g. When placed in a graduated cylinder containing 32.5 ml of water, the volume of the block and water was found to be 54.2 ml. Calculate the density of the metal block and express it in correct units. Show all work. PART 3: Precision and Accuracy when Dispensing Liquids Using your own words, write definitions for the following. You can use your chemistry textbook (Appendix A) to get information, but write in your own words. • Precision • Accuracy • Systematic errors • Random errors2Lab Assignment Part I: Exploring physical and chemical properties Work in pairs. Carryout the following experiments and record your observations. Determine whether your observations warrant a physical property or a chemical property. Experiment Observations Physical/chemical property Do this in the hood. Clean a piece (about 2 inches long) of magnesium ribbon. Using forceps to hold the ribbon, hold it to the flame of a Bunsen burner. Leave a piece of ice on a dish for 10 minutes Pour out approximately 25 ml of vinegar into a beaker. Add about one tablespoon of baking soda to the beaker. Clean up all glassware when you are done. Take a piece of aluminum foil (2”x 2” will be enough). Roll into a dense ball and place it in a tray filled with water. Observe the test tube filled with solid iodine placed in hot water (in the hood)3PART 2: Density Measurements Work in pairs. You are provided with four unknown samples. Two of them are liquids and two are solids. These are pure substances. Your task is to determine the density of these samples. Then use this density data to identify the unknowns. You will need to refer to a standard table that gives you the densities of pure substances (use your chemistry textbook or the Hand Book of Chemistry and Physics available in Lab Stores). Be sure to cite the references used. • When determining the mass of substances, use the analytical balance that enables you to weigh to the nearest 0.0001 grams. • When determining the volume of solids use the displacement method only. First weigh the dry solid sample. Add a known volume of an appropriate liquid to a graduated cylinder (3-5 ml is a good volume to begin). Then add the weighed solid and read the displacement. • When determining the volume of liquids, use a burette to obtain the required volume. A burette will be set up in the lab for each unknown liquid. Find this burette. Take a covered (with an aluminum foil), pre-weighed beaker to the burette. Dispense about 5 ml of the unknown liquid into the weighed beaker and cover with the foil. Be sure to record the exact volume of liquid you dispensed. Now weigh the covered beaker again and determine the mass of the liquid. • In all cases report the mass, volume and density data to the correct number of significant figures. (You can use your Chemistry textbook to learn more about significant figures). • Measure and record room temperature. You will need this for density information. • Report your data in tabulated form (example shown below) in your lab notebook. Be sure to include the correct units for each measurement. The following table will work well for solid samples. Construct a similar one for liquid samples. Unknown Substance A B C etc. Room temperature Mass of the unknown Liquid used for displacement Volume of liquid Volume of liquid + unknown Volume of unknown Density of unknown Identity of the unknown Reference used for identification Do these calculations at home Note: The following instructions pertain to reading a volume in a graduated cylinder, a burette or any other graduated device. 1. Place a piece of white paper or card directly behind the cylinder at the meniscus. 2. Do not hold the graduated device in your hand. Rest it on a tabletop. Then, position your head so that your eye is at the same height as the level of the liquid. 3. Look straight at the meniscus through the glassware so that you see only a concave line not a concave surface. 4. Read the level of the liquid at the bottom of the meniscus, the curved surface of the liquid.4PART 3: Precision and Accuracy when Dispensing Liquids This portion of the lab enables you to understand more about accuracy, precision, random errors and systematic errors in scientific data. Introduction: You will use a 10.00 ml volumetric pipette to obtain a fixed volume of water. You will weigh