# Highline Community College Pre 1982 Penny Lab – Assignment Help

I’m working on a chemistry question and need a sample draft to help me learn.

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1.)After verifying your data on the Lab assignment, complete the calculations for the density for each trial, and then report the average. Do this for both pre-1981 pennies and post-1983 pennies in the table below.

 Pre-1981 Pennies Post-1983 Pennies Trial 1 Trial 2 Trial 1 Trial 2 Density g/mL g/mL g/mL g/mL Average Density g/mL g/mL

Your results from Part A should have demonstrated that the pennies from these two eras have different compositions. One type of penny is mostly copper (95%) with a thin layer of zinc (5%) while the other penny is mostly zinc (97.5%) with a thin outer layer of copper (2.5%).

If the density of copper is 8.96 g/mL and the density of zinc is 7.13 g/mL, determine which penny is which based on your results.

Fill in the statements below with “pre-1982” or “post-1982” based on your results.

The penny is mostly copper (95%) with a thin layer of zinc (5%).

The penny is mostly zinc (97.5%) with a thin layer of copper (2.5%).

Write in complete sentences to support your choice based on your experimental data and results.

2.)Based on the data from the video for Density of an Unknown Liquid and a Mixture, calculate the following results below (recall, each liquid was measured to 10.0 mL):

 Unknown Liquid 50/50 Mixture Mass of liquid g g Density of liquid g/mL g/mL

Ethanol (or ethyl alcohol) is the specific type of alcohol present in alcoholic beverages like beer, wine, vodka, etc. When ethanol is added to water, the two liquids mix completely with one another. At room temperature, ethanol’s density is 0.789 g/mL while water’s density is 0.997 g/mL.

A student is given an unknown alcoholic beverage in a beaker to analyze at room temperature, so the student puts a piece of ice in the unknown liquid and observes that the ice drops below the surface and floats in the middle of the liquid. Based on this observation above and given ice’s density is 0.917 g/mL, what can you conclude about the density and composition of the liquid?

Complete the following with “pure ethanol”, “pure water”, or “a mixture of the two”:

The liquid is .

If it is a mixture, use density to determine if it contains more ethanol or more water, then write in complete sentences to explain your conclusions.

3.)In your calculation of the density of the unknown liquid (in Part B, question 2 above), which measurement limited the number of significant figures in the reported density: volume or mass? Suppose a student wanted to determine the density with more precision. He decided to retake the mass of the liquid on the analytical balance because he feels this will provide more precision for the experiment. Explain whether or not this an effective approach.

4.)In Part C of the experiment, you determined the density of CO2 gas. You may review this data in the prior assignment. How does the density of CO2 compare to the density of the pennies and the unknown liquid and other solids and liquids included in Table I on page 25?

What can you conclude about the density of gases compared to the densities of liquids and solids? Based on the arrangement and number of particles in solids, liquids, and gases, explain why the densities of gases are so different from the densities of solids and liquids.

5.)A substance of higher density will sink in a substance of lower density: For example, you may know that oil floats on top of water because it has a lower density. For each of the following pairs, determine whether the object will sink or float. Refer to Table I on p. 27 and your experimental results to determine each.

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