Density Lab



Density Lab! Tuesday October 3rd & Wednesday October 4th

Write up is due Friday October 5th

Do these things before the lab:

1. In your lab notebooks, write down the title of this lab. Leave a space to fill in the date and your lab partners’ names.

2. Read through the entire lab instructions. Once you have done this, prepare data tables for the three sections of this lab so that when you are making measurements you have an organized place to put them. I will be grading you in part on how well you create these data tables.

3. After each empty data table that you prepare, make sure that you leave yourself room to write down at least three observations (can be all qualitative or quantitative, just have 3 of them for each section).

4. Be familiar with the analysis questions at the end of this write-up! You can answer them in your lab notebook.

The lab itself:

Section I: Density of liquid water.

Materials needed:

1 graduated cylinder

1 reservoir beaker (250 or 400 mL) to pour from/back into

At least 50 mL of water

You will be calculating the density of 10 mL of water, 20 mL of water, 30 mL of water and 40 mL of water.

Remember that density = mass ÷ volume.

You will use the graduated cylinder to measure out each volume. Remember to read from the bottom of the meniscus! You will be measuring the mass of the water when it is in a 100 mL beaker using the triple beam balance. How will you calculate the mass of just the water and not water + beaker? Be sure to show me how you account for this in your data tables!

Section II: Density of solid water (ice!)

Materials needed:

4 ice cubes

Once you are finished with section I, measure out a volume of water that will fill up one ice-cube form. Make a note of this volume! Pour into ice-cube tray. Do this 4 times. Place masking tape with your group # and period # over your forms so that when you get back to this part of the lab, you can retrieve your group’s ice cubes.

Once ice cubes have frozen: determine mass of ice cubes. Handle them with Kleenex so they melt more slowly. Do not place them directly on triple beam balances! Place them on a Kleenex first. How will you calculate the mass of just the ice cub and not ice cube + tissue paper? Be sure to show me how you account for this!

Once you have determined the masses of all four of your ice cubes, put them in the sink.

Section III: Density of money! Well, just pennies.

Materials needed:

10 pennies of at least 5 different mint dates

Graduated cylinder

1 reservoir beaker (250mL or 400mL)

At least 50mL of water

Section III cont’d:

If you have more than 5 different mint dates, it is ok.

You can measure the mass of each penny by placing each one directly on the triple beam balance.

Once you have done this you can measure the volume of each penny. Fill your graduated cylinder with 20 mL of water. Drop all 10 pennies in and measure the change in volume. That change will be the volume of your 10 pennies. Divide by 10 to obtain the average volume of each penny.

Once you have mass and volume, you can calculate density for each penny.

Re-read pages 38 – 39 for guidance on how to set up data tables for this section of the lab. Your charts should include at least the same amount of information as the ones in the book.

Section IV: Density of various liquids (Qualitative observations!)

Materials needed:

~ 20 mL oil

~ 20 mL vinegar

~ 50 mL water

Salt

2 small beakers

In one beaker pour about 50 mL of water. In the other beaker, pour about 25 mL of vinegar. Into both beakers pour about 20 mL of olive oil.

Make observations as to how the liquids mix (drawings might be helpful!).

Add the vinegar/olive oil mixture to your water/olive oil mixture. Make observations as to how the liquids mix (drawings are helpful!).

Shake salt about 5 times on top of your vinegar/water/oil mixture. Make observations as to what happens over the next 2 minutes (draw!).

Analysis Questions – answer in COMPLETE sentences after the lab. Worth 1 quiz grade.

1 – 1. (4 points) Why did I have you measure the density of 10mL, 20mL, 30mL and 40mL of water?

Hint:

Extensive properties = properties of matter that depend on the quantity of matter

Intensive properties = properties of matter that are the same no matter how much matter there is

2 – 1. (4 points) Which has a greater density, liquid water or ice?

3 - 1. (4 points) List the mint dates for the pennies that you tested, from least dense to most dense.

3 – 2. (2 points) What is the density of copper metal?

3 – 3. (2 points) What is the density of zinc metal?

3 – 4. (2 points) Which year that you tested had the most copper?

3 – 5. (6 points) For the mint dates of your most dense and least dense pennies, go online to this website: and look up the prices (in 1998 dollars) of copper and zinc during each of those two years. Clearly state the units (dollars per _____ of copper/zinc).

4 – 1. (4 points) Which liquid was the most dense? How do you know this?

4 – 2. (4 points) Which liquids were the least dense? How do you know this?

4 – 3. (2 points) Which liquids mixed when you combined your two mixtures?

4 – 4. In chemistry, we say “like dissolves like.” Why does this explain what you saw when you combined your two mixtures?

4 – 5. (2 points) Why did the salt fall to the bottom of the beaker?

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