mechanical chemical digestion

1. Body Works
Activity 14B: Breakdown
October 1, 2014

2. Activity 14B: Breakdown
October 1, 2014
Getting Started: Which would dissolve faster, complete uncut rib-eye steak or a
rib-eye steak that has been cut into pieces? Explain your reasoning.
Introduction: Read and summarize pg B-19 in one sentence.
Breakdown
You already know the organs in the digestive
system. But what exactly do they do? One
important function of the digestive system is to
break down food into smaller pieces. Only then
can the nutrients in the food be absorbed by your
body…
Why is it important to chew your food?
14B
Challenge: Rewrite the challenge question in your own words.

3. Key Words: Chemical Breakdown, control, digestive system,
function, mechanical breakdown, organ, qualitative/quantitative
data, surface area, variable
Procedure: Have you read and do you understand the procedure
part A on pg. B-20? Write one sentence that
describes what you will be doing.
Results: The Model
Elements of the digestive process
Student Sheet 14.1 Human Digestive System
Analysis: Discussion
Questions
Reflection: How can understanding how your liver works help
you make decisions about your health?

4. Elements of the Digestive Process
• How did you decide when the chemical
breakdown was over? Did you observe or
record how long it took before the tablet
piece completely dissolved?

5. Testing the Model
• What are your observations? What did you
see, hear, smell?
• Based on your observations, why your think it
is important to chew your food?

6. Key Words: Chemical Breakdown, control, digestive system, function, mechanical
breakdown, organ, qualitative/quantitative data, surface area, variable
Procedure: Have you read and do you understand the procedure
part B on pg. B-21? Write one sentence that
describes what you will be doing.
Results: Pre-Lab and pre-lab discussion
Conduct Experiment
Work on Bar-Graph
Student Sheet 14.1 Human Digestive System
Candy Time
Analysis: Complete Conclusion

7. Experimental Design Elements
Independent and Dependent Variables
Hypothesis
Controlled Variables

8. Independent and Dependent Variables
• Independent Variables (IV)
– IV means “I” control
– It’s the part of the experiment you are testing.
• Dependent Variables (DV)
– DV depends on the IV
– It is the thing you are measuring

9. Example
• IV - food people eat
– Dr. Goldberger decided to test if food was causing
people to get sick so he gave some people fruits
and vegetables and others corn, fatback, and
syrup.
• DV – whether or not people get pellagra
– Dr. Goldberger checked the people to see who got
Pellagra and who did not.

10. What is the independent variable?
• Asked another way: What are we testing?

11. What is the dependent variable?
• Asked another way: What are we measuring?

12. Hypothesis
• Educated guess or prediction
• Always stated:
– If IV then DV
– This means you plug in the independent variable
where it says IV and plug in the dependent
variable where it says DV and rewrite your
hypothesis.

13. Example
• Using the Dr. Goldberger example.
– IV = different types of food
– DV = if they got pellagra
• Write a hypothesis that follows the format:
If IV then DV
If different types of food then if they get Pellagra
If people eat food with vitamins then they will not get
pellagra.

14. Controlled Variables or Constant
Variables
• Different then control or control group.
• These are things that could change every time
you did the experiment if you didn’t control
them.
– Take Dr. Goldberger’s experiment.
These are all things that could
effect the experiment so they
have to be done exactly the
same for each person.
• We assume the patients all ate exactly the same diet
maybe they didn’t.
• Or if some exercised while others did not.
• Or if some were able to shower and wash while others
were not.

15. • What are some of the variables we need to
keep the same in this experiment? How will
we control them?

17. Pre-Lab Discussion
• Question we are trying to answer
– How does the size of your food affect the speed at
which chemical breakdown occurs?
OR
– Does the amount you chew your food affect your
ability to digest it chemically?

19. Candy Time
• Some of you will get a piece of candy that is
whole (complete). The rest of you will get
candy that has been broken down into smaller
parts.
• Time how long it takes you to finish your
candy.
• Record what your body was doing on student
sheet 14.1 and how that helped in digestion.

20. Conclusion
• Restate your hypothesis and explain whether
it was correct or incorrect. Use data you
collected to support your answer.
• Restate the problem statement and answer it
using data you have collected.

21. Amt of
vinegar
(mL)
Time to dissolve (sec)
1 2 3 4 5 6 7 Total
0
2.5
5
10

25. Analysis Question 2
• What part of digestion was modeled by
breaking the tablet?
• What part of digestions was modeled by
adding the vinegar?

26. Analysis question 4
• How does the size of your food affect the
speed at which chemical breakdown occurs?

27. Analysis Question 5
• Besides preventing choking, why is it
important to chew your food?