NAME BLOCK Density Lab PROBLEM: How can we determine the densities of different substances? PART 1 Determining relative density procedure 1. Designate an eyedropper for each beaker. Do not mix them up when you experiment or your results will be off! 2. Use the test tubes for experimenting (do NOT use the beakers for the tests). You will design several different experiments to compare the densities of the liquids and answer the questions posed in the chart. You may mix and match the different liquids in the test tubes as you please to arrive at your answer. Record your procedure for each experiment in the "what I did" column. Record your results (what you saw) in the "what I observed" column Be specific of what you did first, next, and so on so that anyone in the class could follow exactly what you did and get the same results. WARNING--you barely have to use any liquid to get results. These experiments are sensitive. When adding liquid to a test tube hold the test tube at an angle and add the liquid drop by drop. Don't just squeeze out the entire eyedropper at once TIP- it is sometimes difficult to see the color of the liquid when you are using so little of it. By holding a white sheet behind the test tubes you will be able to more easily see your results. 3. After completing each experiment dump the test tube liquid into the sink.
QUESTION WHAT I DID WHAT I OBSERVED 1. Which is denser: solution A or B? Answer: 2. Which is denser: solution B or C? Answer 3. Which is denser: Solution A or C? answer: 1. If something floats in a liquid, then its density is (greater, less than, equal to) the density of the liquid it is in. If something sinks, then its density is (greater, less than, equal to the density of the liquid. 2. List the three solutions in order of increasing density:
PART 2: Calculating Density (include proper units with your answers) 1. Place your empty graduated cylinder on the scale to determine its mass. Record the mass. 2. Measure out 20.0 ml of solution A into the graduated cylinder. Get its new mass and record it here. 3. The mass of 20.0 ml of liquid A is equal to the new mass the empty graduated cylinder. Record this value in mass column in the chart below 4. Calculate the density using the formula mass/volume and record your answer to two decimal places in the chart below. 5. Pour the 20.0 ml of liquid A back into beaker A and rinse out the graduated cylinder. Shake out the excess liquid as best as possible. 6. Now pour 20.0 ml of liquid B into the graduated cylinder and measure its mass (remember to subtract the empty graduated cylinder mass from the new mass) Record in the chart below. 7.Calculate the density of liquid B (record to two decimal places) and record in the chart. 8. Pour liquid B back into Beaker B. Rinse out the graduated cylinder and shake out the excess water. 9. Pour 10 ml of liquid C into the graduated cylinder. Measure its mass and record it below. Then calculate its density and record it below 10. Pour liquid C back into the beaker 11. At the top of each column in the chart, record the units Liquid Mass in Volume in Density in A 20.0 B 20.0 C 20.0 Look at the calculations of your densities and compare it to your results from Part 1. Did you end up with the same sequence as you did in part 1?. If the order doesn t match, you did something wrong. What could be a source of your error? Why might the results not match up?(be specific) Part 3 Density of an object (use proper units with your answers) 1. First find the volume of the cube. Use a ruler to measure the side in cm, then multiply by length x width x height = 2. Find the mass of the cube. And record here: 3. Calculate the density of the cube = 4. Use water displacement method to determine the volume of the fishing lure by filling an empty graduated cylinder with 20 ml of water. Add the lure. The volume is equal to the new volume the original volume = 5. Get the mass of the fishing lure and record it here: 6. Find the density of the fishing lure:
Clean up: Please set up your station exactly how it was when you came in. Leave alone the beakers of solutions A, B and C Rinse out the three small test tubes and return them to the rack. Rinse out the graduated cylinder Clean up all spills and toss all paper towels in the trash Return all objects Conclusions: 1. Look back at your density values of the liquids and the density values of the wood block. Compared to the density of liquid A, the density of the block is (more than/less than/ the same) and, therefore, if placed in liquid A the block would (float, sink, hover in the middle) in the liquid. Compared to the density of liquid A, the density of the fishing lure is (more than/less than/ the same) and therefore if placed in liquid A the fishing lure would (float, sink, hover in the middle) in the liquid. 2. Below is a beaker containing all three liquids that have been layered. Color in where you would expect to find each layer and label the solution. 3. Draw on the diagram above a square to show where the block would be located. Draw in a circle to represent the fishing lure. Calculations 1. If the mass of a substance stays the same, what would you need to do to its volume (increase/decrease) in order to decrease its density? 2. If the volume of a substance is constant, but its mass increases, its density would (increase/decrease) 3. Your earth science teacher gives you a bar of clay and asks you to calculate its density. She then instructs you to cut the bar in half and again calculate its density. Is the density of the half bar of clay GREATER THAN, LESS THAN, or EQUAL TO the density of the whole bar? Explain your answer. 4. Mercury, a liquid at room temperature, has a density of 13.55 g/ml. Calculate the mass of a 50-ml sample of mercury.
Scenario---density challenge---study the three diagrams below showing objects in three different solutions. Use your reasoning ability to try to compare the densities of the objects and the solutions. Assume objects having the same shape have the same density. Liquid line BEAKER X BEAKER Y BEAKER Z 1 Which liquid: beaker X or Y is less dense? How can you tell? 2. List the objects (triangle, square, circle) in order from least to most dense 3. What can you infer would happen if the sphere were placed in beaker Z? Explain how you know 4. What is the density of the sphere in beaker X compared to the liquid in Beaker X?