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Jordyn Smith – January 2016
Doctor Doctor
In this activity, students will act as doctors for the day. They will use Chemistry to
diagnose and treat various medical problems.
Learning Goals: The goal of this experiment is to show students the connection between
the Chemistry concepts they learn in school and certain medical diagnoses. First, all
students come together to watch a demonstration of hydrogen peroxide decomposition in
the presence of a yeast catalyst. The concept of catalysis will be used to help students
understand lactose intolerance. They will then perform activities to understand the
concept of solution concentration using color change (qualitative) and conductivity
(quantitative). They will use this concept to diagnose and treat dehydration. Students will
do another exercise that illustrates neutralization. They will then use this concept to treat
acid reflux.
Recommended Grades: 4th – 6th grade.
Estimated Time Required:
a) Preparation Time: 15 minutes
b) Class time: 45 minutes
Key Concepts:
Concentration: amount ÷ volume. Concentration is a measure of the amount of a
substance present in a certain volume. If two cups of salt water, A and B, have the same
volume, but cup B has more salt than cup A, cup B is a more concentrated salt solution.
Conductivity: a measure of the ability of a solution to conduct charge. A more
concentrated salt solution will have a greater conductivity because there are more
dissolved ions capable of conducting charge.
Qualitative vs. quantitative: A qualitative observation is made using the five senses. It is
presented in the form of a description (ex: color). A quantitative observation is presented
in the form of a numerical value, often with a unit of measurement (ex: conductivity).
pH scale: The pH scale is a way of identifying and organizing acids and bases. Acids
have pH values of 0 – 6 and bases of 8 – 14. pH 7 is neutral and is the pH of water.
Neutralization: Neutralization occurs when an acid and a base react with each other.
Upon neutralization, the pH of the reaction solution tends toward 7.
Catalysis: Some reactions naturally occur at very slow rates. The addition of a catalyst
alters the reaction pathway, providing a faster mechanism for the reaction. Biological
catalysts are called enzymes. People who lack the enzyme lactase cannot digest lactose
and are therefore called lactose intolerant.
Materials for 1 class of 4 or 5 groups: (1 group = 3 or 4 students)
- 4 L deionized water
- 20 250 mL capacity plastic cups
- 1 bottle of blue or green food coloring per group
- 1 bottle of yellow food coloring
- 300 g of table salt (NaCl)
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20 pieces of universal pH indicator
2 conductivity probes with appropriate wash bin and soaking beaker.
2 deionized water squirt bottles.
1 roll of tape
1 permanent marker
1 measuring spoon (of varied capacities) per group: ½, ¼ and 1/8 tsp.
red, green and blue markers or crayons
1 bottle of lemon juice
1 bottle of household ammonia
½ tsp of yeast
½ cup of hydrogen peroxide 3%
100 mL of Mg(OH)2
100 mL vinegar
100 mL grapefruit juice
5 100 mL plastic cup with a marking at 90 mL (per group)
20 popsicle sticks
16 100 mL plastic cups with lids
30 clear film canisters
1 plastic tray container
1 plastic 300 mL cup
Estimated Cost: $10
Safety Information: Everything used in this experiment can be disposed of in the trash
or sink. Household ammonia is not corrosive to the skin but will burn the eyes so teachers
will pre-pour cups of ammonia for students.
Procedure:
Set up:
1.) Divide the class into groups of 3 or 4. In front of each group, place 4 plastic cups
with a black marking at the same spot on each cup. Place an abundance of
deionized water and one bottle of blue or green food coloring at each table. Label
the first cup “1 drop,” the second cup “2 drops” and so on for “3 drops” and “4
drops.”
2.) Prepare 3 cups of 80 mL of water and place a weigh boat or jar of table salt
(NaCl) beside these cups. Label the cups: ½ ¼ and 1/8 tsp.
3.) Before students arrive, prepare a cup of 80 mL of water, 3 drops of yellow food
coloring and 1/2 table salt. This is the urine sample. Keep this aside as it is for
later.
4.) Plug in the conductivity probes and always leave them to soak in water.
5.) In front of each group, place one film canister of 6 mL lemon juice and one of 3
mL ammonia. Also place 3 pieces of universal acid base indicator.
6.) In the closeable plastic containers, pour vinegar, Mg(OH)2 and grapefruit juice.
Label the containers A, B and C. Place an A, B and C at each table.
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7.) In a plastic tray container, place a 300 mL plastic cup. Pour ½ cup of 3%
hydrogen peroxide in the cup, and prepare half a teaspoon of yeast to be added
later. Food coloring can be added to the hydrogen peroxide to make it look cooler
for the kids.
Opening Discussion:
1. Introduction and welcome.
2. Today we are at the doctor’s office, but all of the doctors are snowed in at home.
3. The patients are here and they need your help.
4. Who knows anyone lactose intolerant?
5. What does it mean?
6. Does anyone know what a catalyst is? Explain that a catalyst makes a slow
reaction go faster.
7. Explain that lactase is a catalyst that breaks down lactose in milk and cheese.
People who don’t have lactase are lactose intolerant.
8. The same is true in the reaction demonstration. Hydrogen peroxide is like the milk
and the yeast is like lactase. Lactose intolerant people are the reaction currently –
stagnant – but people who have lactose are: mix yeast in hydrogen peroxide and
stir. A vigorous foaming reaction will result.
Transition to the next part of the activity. Students sit in their groups.
9. Explain that concentration is amount/volume. Ask: The four cups before you
have the same volume of water, but we’re adding more drops to some than others.
Which cup do you think will be the most concentrated? Students should answer
aloud and on worksheet.
10. Tell students to add the number of drops of food coloring that is indicated on each
cup.
11. Ask them what they notice about the color of each cup (gradation of color with
more drops).
12. Students answer Worksheet part 1. Help prompt them by explaining that a
measurement you see, feel or touch is qualitative. Explain that there is also a
quantitative way to judge concentration: conductivity.
13. Explain: When you add salt to water, it splits into positively and negatively
charged ions that are able to carry electricity. Ask: What do you think happens to
conductivity with more charge? Therefore, which cup do you think will conduct
the most electricity?
14. Tell students to add the amount of salt indicated on the label of their cup. Each
group has either ½, ¼ or 1/8 tsp.
15. Show students the conductivity probe and tell them: This machine is called a
conductivity probe. It judges if any electricity is being transferred through a
liquid.
16. One student from each group will bring their cup over to the conductivity probe.
Students will take turns using the probe to record the conductivity of each
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solution. The students should then go to the blackboard and write down their
group’s measurement.
17. Students answer Worksheet Part 2.
18. Ask students: are you guys ready to be doctors now?
19. Tell students: a patient came in yesterday saying she wasn’t feeling well. Her
head hurt and she was really tired. She had been doing a lot of running. We asked
her to do a urine sample, and this is her urine.
20. Show students the yellow, saline cup of water.
21. Asks students what they think the problem is. Tell them to look at their
worksheets.
22. Prompt students to establish that this urine is very dark yellow and have one
volunteer take the conductivity. Have students record it on the worksheet. They
should note that it is higher than the healthy range given on the worksheet.
23. Prompt students to discuss how the urine is very concentrated, and that the patient
might be dehydrated. Prompt a discussion about how to dilute the solution and
that the patient should drink water. Demonstrate this by pouring water into the
urine cup so they see the color dilution. Students can then take the conductivity
again and see a drop.
Transition to next part of the activity.
1.) Ask students: What do you know about acids and bases? (Let students answer).
Explain: acids and bases are substances that act in different ways. An example of
an acid found in your house is grapefruit juice and a base is baking soda or
window cleaner (you can’t eat the bases in this case!).
2.) Ask students to look at their worksheets. Say: As you can see, acids and bases are
organized on the pH scale. 0-6 are acids, 7 is neutral (not an acid or base) and 814 are bases. Are you ready to test this out?
3.) Tell students to dip one end of the orange indicator in the lemon juice on their
table. Tell them to record the color it turns on their sheet and use the pH scale to
see if it is an acid or a base.
4.) Repeat the process with ammonia.
5.) Ask students: what do you think happens if you mix the acid and base together?
Go ahead and try it! Students can pour one liquid into the other. At this stage,
hand out fresh orange indicator papers. Tell students to test the color change and
record if it’s an acid, base or neutral. Ask the students what happened when they
combined an acid and a base. Look for an answer about “cancelling each other
out.” Explain: When an acid and base come together, they react to make
something neutral. It’s called neutralization. Tell them to answer the last question
on worksheet page 3.
6.) Tell students: Look at the back of your worksheet. Does someone want to read the
first line out loud? (If students are older, just have them read it). Take a look at
that diagram. Does anyone know about where acid might be found? Clue: acid
breaks down food. Prompt students toward the stomach and have them color it
red. Say: Now, who can guess what brings the food to the stomach? Prompt
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students toward the esophagus, tell them to color it, and have them color the
mouth according to the worksheet instructions.
7.) Students read the medical problem below the diagram on the worksheet.
8.) Ask: How could we get rid of acid in the green organ, based on the activity you
did before. (Add base) Students answer on the worksheet.
9.) Put out the three medicines (A, B and C) and give students another piece of
indicator. Let them test the medicines and help them complete the table and
question on the worksheet to determine the correct medicine. Tell them this is
exactly how TUMS work.
Possible Variations and Additions
Malnutrition: If teachers want to address issues of malnutrition, an activity involving an
iodine test for starch can be performed. Students can be told that a patient is carbohydrate
deficient. The students must determine what food the patient should consume by testing
various foods for starch using the color change produced by iodine. Potato should be the
positive test and easily accessible fruits and vegetables, such as apples and celery, can be
the negative tests.
Asthma/Pulmonary Inflammation: Teachers can discuss the impact of asthma and
alveolar inflammation by using balloons blown up to different sizes. Students can
visualize that the larger balloons hold more air. When the alveoli are swollen, they hold
less air, causing symptoms of shortness of breath and wheezing with which students will
likely be familiar.
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Jordyn Smith – January 2016
NAME:
DATE:
DOCTOR DOCTOR
concentration station
Part 1:
Concentration =
𝒂𝒎𝒐𝒖𝒏𝒕
𝒗𝒐𝒍𝒖𝒎𝒆
If all the cups have the same amount of water, which cup do you think
will be most concentrated? _______________
What do you notice about the color of the cups as you add more drops?
------------------------------------------------As the solution gets more concentrated, the color gets ________.
Circle the correct answer:
This is a quantitative / qualitative measurement.
Part 2:
Concentration =
𝒂𝒎𝒐𝒖𝒏𝒕
𝒗𝒐𝒍𝒖𝒎𝒆
=
𝒕𝒔𝒑
𝟖𝟎 𝒎𝑳
=
Fill out this table:
Cup
Concentration
(tsp/ 80 mL)
1
tsp /80 mL.
Conductivity
(ms/cm)
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Jordyn Smith – January 2016
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As the solutions get more concentrated, the conductivity
__________ .
Part 3:
The normal color of urine is pale yellow and conductivity is
between 5 and 15 ms/cm.
The color of this urine is ___________ and the conductivity is
_______ ms/cm.
The problem is: _________________________
The patient should: _______________________
What happened when you added water?
-------------------------------
NAME:
DATE:
DOCTOR DOCTOR
stomach ache!
Complete this table:
substance
Color of indicator
acid or base or
neutral?
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Jordyn Smith – January 2016
Lemon juice
Ammonia
Mixture
pH scale and indicator:
ACIDS
neutral
BASES
What happened when you put the acid and base together?
________________________________________________________
A patient comes to you complaining of a burning tightness in his
chest. It happens only after he eats.
Color a very acidic organ in RED.
Color the organ that brings food to
the red organ in GREEN.
Color the mouth in BLUE.
http://www.niddk.nih.gov/health-information/healthtopics/Anatomy/your-digestivesystem/PublishingImages/digest.jpg
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Jordyn Smith – January 2016
Sometimes, acid from the RED organ can go backwards into the
GREEN organ. This is painful.
How could you get rid of the acid in the GREEN organ?
- - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - -- - - - - - - - - - - - - - - A, B and C are possible medicines your patient can take.
Complete the table:
Medicine
Acid or Base
Should patient take
it?
A
B
C
The right medicine to give to the patient is : _________.
References:
“Measuring Concentration.” Biomedx. Biomedx Group, 2015. Web. Jan 15. 2016.
http://biomedx.com/conductivity/