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Assignment 1.5 Identifying Variables Worksheet
Points Possible: 10 points
Name_________________ Date________ Block_____
Instructions: Complete sides 1 and 2 of this worksheet for homework. Be prepared to discuss any of the items in this
worksheet during class. Analyzing the parts of a given experiment scenario will be included on your Unit 1 Quiz.
Points Possible: 10 points based on participation in group work and whole-class discussion.
Introduction: Use your materials from Unit 1 to define the following parts of a controlled experiment.
1. Hypothesis ____________________________________________________________________________________
2. Independent variable ____________________________________________________________________________
3. Dependent variable ______________________________________________________________________________
4. Experimental version _____________________________________________________________________________
5. Control version __________________________________________________________________________________
6. Constants _______________________________________________________________________________________
7. Group size ______________________________________________________________________________________
8. Number of trials _________________________________________________________________________________
9. In Science experiments, it is very important to “control the variables” so that there is only ONE independent variable
and ONE dependent variable. We “control the variables” by making anything else that could change during the
experiment into a constant. For example, if you are doing an experiment to find out what material can hold more
water, then it is important to make sure all the materials you are testing are the same size. Why is it so important to
control the variables? What would happen if we did not control them?
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Analyze Experiments: Read each of the scenarios below. Identify the variables for each example in the lines provided.
Experiment 1
Leo wondered if penicillin prevents infection. His hypothesis was: If the medicine prevents infection, than the medicine
will prevent the growth of bacteria that cause infection. Leo placed two identical circles of paper in a Petri dish
(something used for growing bacteria). One circle of paper was soaked in penicillin. The other had nothing on it. He
poured a liquid filled with E coli bacteria into the Petri dish. Both circles of paper were placed in the Petri dish about 3cm
apart. The temperature was kept at 80 degrees Fahrenheit throughout the experiment. At the end of the experiment, a
blank circle with a radius of 2cm formed around the circle of paper soaked in penicillin. There were no bacteria growing
inside the 2cm circle. No change had occurred around the other circle of paper. The bacteria were growing well.
hypothesis ________________________________________________________________________________
independent variable ________________________________________________________________________
dependent variable __________________________________________________________________________
experimental version _________________________________________________________________________
control version______________________________________________________________________________
constant ___________________________________________________________________________________
group size __________________________________________________________________________________
number of trials _____________________________________________________________________________
Experiment 2
Sara Lilia was curious about how different types of music affect how well a person can do his/her homework.
Her hypothesis was: Music that does not have a strong beat makes concentrating on a homework assignment easier.
Music with heavy beats makes concentration more difficult. During her experiment Sara Lilia pulled out four different
CD’s to find out which type helped her to finish her homework the fastest. The first CD was rock, the second reggaeton,
the third classical, and the fourth was cumbia. She chose a math assignment that required concentration. Sara Lilia used
a stopwatch with an alarm to make sure that she only listened to each CD for 5 minutes. Each time the alarm went off,
Sara Lilia recorded how many problems she was able to finish. At the end of the experiment, she found that she was
able to concentrate the most with the classical music, then the rock, and the cumbia. She noticed that she did not
concentrate much at all with the reggaeton and felt like dancing and singing along instead of working.
hypothesis __ Music that does not have a strong beat makes concentrating on a homework assignment easier .
independent variable ________________________________________________________________________
dependent variable __________________________________________________________________________
experimental version _________________________________________________________________________
control version______________________________________________________________________________
constant ___________________________________________________________________________________
group size __1, she was her own test subject________________________________________________
number of trials _1, the experiment was completed one time______________________________
Experiment 3 A Maryland landscaper wanted to see which type of imported rose bush can best withstand the heat of
summer, and could be sold in Maryland. Ten rosebushes native to Maryland and ten imported rose bushes were grown
in their greenhouse with the same amount of water and fertilizer from June through August. The number of flowers on
each bush is counted at the middle and end of the summer.
hypothesis _ see which type of rose bush can best withstand the heat of summer _______________
independent variable ____ type of rose bush __________________________________________
dependent variable ____ The number of flowers on each bush is counted _________________________
experimental version ____ rosebushes native to Maryland _________________________________
control version____ imported rose bushes ____________________________________________
constant _ same greenhouse with the same amount of water and fertilizer from June through August ____
group size _____10 bushes_____________________________________________________
number of trials __1 trial_____________________________________________________
Experiment 4 Elizabeth wanted to know how salt water would affect the growth of plants. She watered three
sunflower plants with salt water. Each plant received a different concentration of salt solutions. A fourth plant received
regular water. After a two-week period, the height of the plants was measured. Her lab partner Lisa also ran this entire
experiment in another classroom.
hypothesis __________ how does salt water affects the growth of plants _____________
independent variable ____concentration of salt solutions________________________________________
dependent variable ______ height of the plants was measured ________________________
experimental version _ plants receiving a different concentration of salt solutions _______________________
control version______ regular water plant________________________________________________
constant ___type of flower (used sunflowers for all groups)________________________________
group size ________1, only one plant was exposed to a certain concentration of salt water or regular water.
number of trials: 2 Her lab partner Lisa also ran this entire experiment in another classroom.
Experiment 5 A garden shop owner in Florida wanted to know how humidity affected wax palm trees. Three wax palm
trees are kept at different humidity levels inside of a greenhouse for 12 weeks. One tree is left outside in normal
conditions. Height of the tree and color of the leaves is measured once a week.
hypothesis How does humidity affect wax palm trees?
independent variable __ different humidity levels ________________________________________
dependent variable __ Height of the tree and color of the leaves is measured once a week __
experimental version Three wax palm trees are kept at different humidity levels inside of a greenhouse _
control version__ One tree is left outside in normal conditions
constant ____ type of tree, all are wax palm trees _______________________________________
group size ______1____________________________________________________________________________
number of trials __1___________________________________________________________________________
Experiment 6 Michael wanted to know the best amount of food needed for his goldfish to survive. He sets up the
following fish tanks: One tank of goldfish is fed the normal amount of food once a day, a second tank is fed twice a day,
and a third tank four times a day during a six week study. The mass of the fish is recorded each day.
hypothesis ___what is the best amount of food needed for his goldfish to survive _____________
independent variable __amount of food_______________________________________________
dependent variable ___ mass of each fish ________________________________
experimental version ____each fish given a certain amount of food (all) ____________________________
control version_______none, you know that not giving the fish its food would kill it._______________________
constant ____all same type of fish_____________________________________
group size ____ 1 tank of fish – do not know how many fish in the tank_________________
number of trials ____1 _____________________________________________________________
Experiment 7 A farm supply company wants to know how much water to recommend for the growth of the strawberry
plants that it sells. They sell strawberry plant clones. Organisms that are cloned are genetically identical to each other.
To find the ideal amount of water needed, the strawberry plant clones are given different amounts of water for a 3week period. The first strawberry plant receives 400 milliliters (ml) a day. The second strawberry plant receives 200ml a
day. The third strawberry plant receives 100ml a day. The fourth strawberry plant does not receive any extra water, this
plant only receives water only during rain fall. The height of the strawberry plants is recorded daily.
hypothesis __ how much water to recommend for the growth of the strawberry plants ___
independent variable ____amount of water given ______________________________________
dependent variable _____height of plants recorded daily_________________
experimental version _____plants receiving water______
control version_____plant getting normal rainfall______________________________________
constant ______genetic makeup of the strawberry plants – they are all clones_______________________
group size _________1 plant___________________________
number of trials ___1__________________________________________________________________________