volume and chemistry - lab aids

Investigation 1B

Volume and Chemistry

2 Investigation 1B: Volume and Chemistry

• How do we measure liquid quantities in chemistry?

• How can we measure very small quantities?


Handling glassware

• Handle graduated cylinders and other glassware carefully.

• Avoid quick or spastic movements that might knock things over, and possibly break them.

• Immediately notify your instructor if there is any broken glass!

• All glassware should be rinsed out and placed on a rack when your lab is finished.


Reading a graduated cylinder

A 100 mL cylinder – marked every milliliter (mL)

• This reads 77.0 mL

• Ignore the edges and read the meniscus –the flat part.


Part 1: Setting up

1. Measure out 100 mL of water into a graduated cylinder.

2. Add 1 drop of food coloring to each of the 4 test tubes. Use a different color for each tube.

3. Add 20 mL of water to each test tube.


A solution is a uniform mixture of two substances – in this case water and dye.

Part 1: Setting up


Part 2: Calibrating a dropper

In the next part of the investigation you will need to know the volume of one drop! How will you determine this small amount accurately?

1. Read and record the volume in milliliters (mL) for 50, 100, and 150 drops from a dropper bottle. Use colored water for readability (Do not use the colored water from your test tubes).


1.6 31 0.0323.24.9

2. Calculate the number of drops per milliliter for each of the 3 volumes.

3. Calculate the volume of 1 drop in milliliters.

50 311.6

1.6 0.03250

drops drops mLmL

mL mL dropdrops

=

=



1.6 31 0.0323.2 31 0.0324.9 31 0.033

31 31 313

0.032 0.032 0.0333

31

0.032

average

averag

drops mL

mL drope

+ += =

+ += =

Using this particular dropper bottle, it took 31 drops to deliver 1.0 mL.

We were also able to determine the volume of a very small quantity of liquid: a drop represents about 0.032 mL.



Just because you can buy bleach in the grocery store does NOT mean it can’t be dangerous if misused.

Bleach can irritate or permanently damage eyes, nose, and mouth.

• Wear safety goggles.

• Work slowly and deliberately.

• Do not drip solutions on skin or clothing.

• If bleach gets on your skin, rinse it off immediately with cold water.

• If bleach gets in your eye(s), use the eyewash and get immediate attention.

• Do not drink or inhale bleach!

Handling chemicals


1. Transfer 3 mL of one colored solution into a smaller test tube.

2. Use the dropper to add drops of bleach. Count the number of drops it takes for the solution to be colorless.

3. Record the number of drops of bleach for each colored solution in Table 2.

4. Empty the test tube, rinse it out, and repeat the experiment with another colored solution. If you have time, do 2 trials for each color.

How many drops of bleach to make the color vanish?

Part 3: A chemical reaction

How much bleach does it take to remove a stain?


a. What makes the color in food coloring?

b. Propose a possible explanation for why the bleach removed the color.

c. Did each color behave the same way? What does that suggest about the different colors?

d. Is the removal of color by bleach the result of a chemical change or a physical change? What evidence supports your claim?

e. Was mixing food coloring in water a chemical change or a physical change?

Part 4: Things to think about


Part 5: A chemical mystery

One of the colors is a mixture of two others. See if you can determine which one is the mixture, and present experimental evidence that supports your claim.


Part 6: Going further

a. Use the data from Table 1 and Table 2 to calculate how many milliliters of bleach it took per milliliters of colored water. This tells you the percent volume of bleach you need to remove each color.

b. Bleach is used in washing clothes because it chemically removes stains. Suppose your washing machine holds 15 gallons of water.

How much bleach would you add to remove a yellow food color stain with the same concentration as your experiment? Use the following equivalents:

1 3,7851 237

gallon mLcup mL

==


Red #40Allura Red

C18H14N2Na2O8S2

Yellow #5Tartrazine

C16H9N4Na3O9S2

Blue #1Erioglaucine

C37H34N2Na2O9S3

GreenMixture of

yellow and blue


Chlorine bleach causes a chemical reaction

What happened?

volume and chemistry - lab aids

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