Name:
Date:
Pd:
GOT MILK?
Research Question: What is the difference between dependent and independent variables?
Purpose: When food coloring and detergent are added to milk, interesting things happen. In this experiment,
you will have the opportunity to observe this phenomenon in order to come up with possible explanations for
what you observe. Also you will identify the difference between dependent and independent variables.
Objectives:
1. Investigate the variables which affect an experiment.
2. Create a testable explanation for the phenomenon.
3. Identify the independent and dependent variable.
Vocabulary Terms: Fill in your definition for the empty vocabulary words.
Testable Hypothesis – a tentative statement that proposes a possible explanation to some action or phenomenon.
Independent (Manipulated) Variable – The variable you are changing (type of detergent)
Dependent (Responding) Variable – The variable that stays the same (milk)
Controlled (Constant) Variable – The experiment which all variables stay the same. No changes made.
Procedure –
Experiment –
Trials –
Data –
Observation Materials:
3 types of Milk: Whole,
2%, Skim
4 colors of food coloring:
Red, Yellow, Blue, Green
Colored Pencils
4 petri dishes
3 types of detergent:
vegetable oil, Dawn dish
detergent, motor oil
Lab Sheet
Pencil
eyedroppers
PRE-LAB: Generate at least 3 possible explanations (predictions) for your observations. What do you
think will happen when we mix all these solutions together? Write in this space below:
1.
2.
3.
Name:
Apparatus (set up):
Date:
Red
Pd:
Veg Oil
Dawn
Motor Oil
Blue
Yellow
CONTROL
Green
Milk ONLY
Milk + Veg. Oil
Milk + Motor Oil
Milk + Dawn
Procedure: NO MORE THAN 3 PEOPLE TO A GROUP. EACH PERSON TURNS IN THEIR OWN
LAB!
1. Assign lab roles within your lab group and collect materials for the lab.
2. Set up the first 4 petri dishes by pouring a SMALL amount of the whole milk (enough to cover the
bottom of the petri dish). Make sure to keep your petri dishes in a straight line on your lab table.
3. Near the edge of the dish, carefully add 1 DROP of each food coloring to the four sides of the petri dish
(top, bottom, left, right – or – North, South, East, West) according to the diagram above.
4. To the first petri dish, add ONLY food coloring. NO DETERGENT. This is your CONTROL.
5. To the second petri dish, add one drop of the vegetable oil to the center of the milk in the petri dish,
observe and record what happens.
a. Draw your observations using colored pencils on your observation sheet. Describe your
observations in the space below.
6. To the third petri dish, add one drop of motor oil to the center of the milk in the petri dish. Observe and
record what happens (Repeat step 5a).
7. To the fourth petri dish, add one drop of DAWN dish detergent to the center of the milk in the petri dish.
Observe and record what happens (Repeat step 5a).
8. Once you record all your observations for the Whole Milk, rinse your petri dishes out in the sink.
Repeat Steps #27 using 2% Milk. Record observations in your data sheet.
9. Once you complete the experiment for 2% milk, clean out petri dishes and repeat all using Skim Milk.
Record observations in your data sheet.
Name:
Date:
Pd:
Got MILK?
Analysis/Conclusion Questions: Answer the following in COMPLETE Sentences!
1. What are the differences between the three types of milk used in the lab?
2. What was the purpose of the food coloring?
3. Based on your observations and drawings, rank the 3 types of milk in order of increasing activity (seen
as movement in the food coloring spreading out) to the Dawn dish soap.
____________________  ___________________________  ___________________________
Least Active
Most Active
4. In your words, explain how dish soap cleans your dirty dishes:
5. What is your independent variable?
6. What is your dependent variable?
7. What is your control group?
8. Why is it important to have a control group?
9. Your mom asks you which type of dish soap she should buy to clean the dishes. Using your experience
in this lab activity, design an experiment to test different types of dish soap. What would your
controlled (control) variable be? What would your independent variable be? What would your
dependent variable be?