Chemnants Lite

In this laboratory students will explore a potpourri of unrelated systems.  In some sections the students will make a prediction and then test their hypothesis.

I. Subtractive Colors: Colors by Absorption, Selective Transmission, and Reflection

In this section you will explore the subtractive primary colors using food color in water.

Blue and Yellow

1. Prediction: What color will blue and yellow make? ______________
2. Use an eyedropper to obtain some blue liquid.
3. Add the blue liquid to your test tube.
4. Rinse out the eyedropper with clear water.
5. Use the eyedropper to obtain yellow liquid.  Try to get the same amount of yellow as the amount of blue you had.
6. Add the yellow liquid to the test tube.
7. Set the test tube against a piece of white paper.  Look at the water in the test tube.  You are viewing light reflected from the liquid in the test tube.  What reflected color did the mixture of blue and yellow make? _________________
8. Hold the test tube up to the light.  Look through the test tube at the light.  You are viewing light transmitted from the test tube.  What transmitted color did the mixture of blue and yellow make? __________________
9. Are the reflected and transmitted colors the same?

Blue and Red

1. Prediction: What color will blue and red make? ______________
2. Rinse your test tube with clear water.
3. Use an eyedropper to obtain some blue liquid.
4. Add the blue liquid to your test tube.
5. Rinse out the eyedropper with clear water.
6. Use the eyedropper to obtain red liquid.  Try to get the same amount of red as the amount of blue you had.
7. Add the red liquid to the test tube.
8. Set the test tube against a piece of white paper.  Look at the water in the test tube.  You are viewing light reflected from the liquid in the test tube.  What color did the mixture of blue and red make? _________________
9. Hold the test tube up to the light.  Look through the test tube at the light.  You are viewing light transmitted from the test tube.  What transmitted color did the mixture of blue and red make? __________________
10. Are the reflected and transmitted colors the same?

Yellow and Red

1. Prediction: What color will yellow and red make? ______________
2. Rinse your test tube with clear water.
3. Use an eyedropper to obtain some blue liquid.
4. Add the yellow liquid to your test tube.
5. Rinse out the eyedropper with clear water.
6. Use the eyedropper to obtain red liquid.  Try to get the same amount of red as the amount of yellow you had.
7. Add the red liquid to the test tube.
8. Set the test tube against a piece of white paper.  Look at the water in the test tube.  You are viewing light reflected from the liquid in the test tube.  What color did the mixture of yellow and red make? _________________
9. Hold the test tube up to the light.  Look through the test tube at the light.  You are viewing light transmitted from the test tube.  What transmitted color did the mixture of yellow and red make? __________________
10. Are the reflected and transmitted colors the same?

Litmus Test

Liquids and substances that dissolve in liquids can be tested to determine whether they are acids or bases using fairly commonly available substances.  Today we will look at whether a substance is an acid or a base using both red cabbage juice and red hibiscus blossom juice.  Note that when the cabbage and hibiscus are boiled a purple colored juice forms in the water.

Normally a special kind of paper called litmus paper is used to determine whether something is an acid or a base.  Litmus solution, however, can be prepared by boiling red cabbage in water and using the purple juice to test whether something is an acid or a base.  Another solution that we will examine today as a possible test solution is made by placing red hibiscus blossoms in boiling water.  The extract is, oddly enough, also purple.

Lemon Juice in Cabbage Juice

1. Rinse out your test tube.
2. Add one dropper full of the cabbage test solution to a test tube.
3. What color is the liquid in the test tube?___________________
4. Rinse out the dropper.
5. Add a couple drops of lemon juice to the test tube.
6. Agitate the test tube to facilitate mixing.
7. What color is the liquid in the test tube?___________________

Vinegar in Cabbage Juice

1. Rinse out your test tube.
2. Add one dropper full of the cabbage test solution to a test tube.
3. What color is the liquid in the test tube?___________________
4. Rinse out the dropper.
5. Add a couple drops of vinegar juice to the test tube.
6. Agitate the test tube to facilitate mixing.
7. What color is the liquid in the test tube?___________________

Baking Soda in Cabbage Juice

1. Rinse out your test tube.
2. Add one dropper full of the cabbage test solution to a test tube.
3. What color is the liquid in the test tube?___________________
4. Rinse out the dropper.
5. Add a small amount of baking soda to the test tube.
6. Agitate the test tube to facilitate mixing.
7. What color is the liquid in the test tube?___________________

Which liquids, if any, caused the same color to appear?

__________________________________________________________

Lemon Juice in Hibiscus Juice

1. Rinse out your test tube.
2. Add one dropper full of the hibiscus test solution to a test tube.
3. What color is the liquid in the test tube?___________________
4. Rinse out the dropper.
5. Add a couple drops of lemon juice to the test tube.
6. Agitate the test tube to facilitate mixing.
7. What color is the liquid in the test tube?___________________

Vinegar in Hibiscus Juice

1. Rinse out your test tube.
2. Add one dropper full of the hibiscus test solution to a test tube.
3. What color is the liquid in the test tube?___________________
4. Rinse out the dropper.
5. Add a couple drops of vinegar juice to the test tube.
6. Agitate the test tube to facilitate mixing.
7. What color is the liquid in the test tube?___________________

Baking Soda in Hibiscus Juice

1. Rinse out your test tube.
2. Add one dropper full of the hibiscus test solution to a test tube.
3. What color is the liquid in the test tube?___________________
4. Rinse out the dropper.
5. Add a small amount of baking soda to the test tube.
6. Agitate the test tube to facilitate mixing.
7. What color is the liquid in the test tube?___________________

Which liquids, if any, caused the same color to appear?

__________________________________________________________

Is the red cabbage juice the same as the red hibiscus flower juice?

__________________________________________________________

If lemon juice is an acid and baking soda is a base, what is vinegar?

__________________________________________________________

Density of Liquids

You will need two cups for this portion of the laboratory.

1. Prediction: Which is more dense, oil or water? _______________________
2. Determine the mass of an empty plastic cup m_c in grams ________________
3. Add 10 ml of water (V_w)to one cup and determine the mass of the cup and the water m_cw ____________
4. Subtract the mass of the empty cup from m_cw to determine the mass of the water m_w _____________
5. Divide the mass of water m_w by the volume of the water to obtain the density of the water d_w _________
6. Add 10 ml of vegetable oil (V_o) to one cup and determine the mass of the cup and the oil m_ow _____________
7. Subtract the mass of the empty cup from m_ow to determine the mass of the oil m_o ______________
8. Divide the mass of oil m_o by the volume of the oil to obtain the density of the oil d_o _________
9. Which is more dense, water or oil? _________________ _____
10. Which will float on top of the other? _______________
11. Pour some of the oil and water into a test tube.  Which floated to the top?
12. Rinse out and wash your cups with soap, and water.  Use a scrub brush as necessary to remove the oil from the test tube.

Homework

1. What color will red, yellow, and blue solution make when all three are combined? __________________
2. If hibiscus flowers are boiled and then added to Kosraen lime drink, what will be the color of the lime drink? _____________________
3. If betelnut lime is added to red cabbage juice test solution, what color will the red cabbage solution turn? ____________________

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