Level 3 Practice Questions
1. Laura wants to see if drinking Gatorade makes people run faster. She gets a group of 10 Da Vinci
students together. Laura makes half of the kids drink 2L of red Gatorade every day, and makes
the other half drink 2L of water. She records all 10 students’ time on a 100m run every day for a
month. At the end of the month, Laura averages the race times for each group. The group who
drank Gatorade runs 100m an average of 0.8 seconds faster than the group who drank water!!
Laura is super excited, and concludes that Gatorade really does make people run faster.
a) What were the independent, dependent, and controlled variables in this experiment?
Independent variable: the one thing that you are changing. In this case, the liquid that the
students are drinking.
Dependent variable: measureable change that occurs because of the independent variable. In
this case, the speed that the students run.
Controlled variables: everything that remains constant across all trials. In this case, the volume
of liquid that the students drink, the distance that the student run.
b) Was Laura’s conclusion well backed with evidence? Explain why or why not.
No—10 students is not a large enough sample group to make big generalizations. Laura forgot to control
lots of other variables, such as the students’ age, gender, diet, and exercise habits. Laura did not
mention whether she used the same equipment to time each trial, whether all students ran at the same
time of day, or whether students ran on the same surface. (there are lots of other possible examples of
missing controls.)
2. Amir is a famous dancer on a worldwide tour in Europe. He wants to see how much cologne he
uses every day while he’s on tour. Amir’s cologne bottle is from the US, so he makes the
following DA chart to convert to metric units. (He needs his stylists to understand the units, so
that they have enough cologne on hand behind stage!) Is Amir’s DA chart correct? Explain why
or why not.
2 bottles of
cologne (amount
that Amir uses
every day)
2.5 oz
1 Liter
1000 mm
1 bottle
35 oz
1 liter
Answer:
1000/7 mm of
cologne
No—Amir’s math is correct, but he converted from liters to millimeters. This is impossible, because liters
measure volume, and mm measure length. It does not make sense to talk about the amount of a liquid
in terms of distance.
3. Look at the two diagrams below. Say which element each one is a picture of. Are they ions,
isotopes, or neutral atoms? How can you tell?
Diagram B is Oxygen, because it has 8 Protons. It is not an isotope, because 8 protons + 8
neutrons = 16, which is the mass number given on the periodic table. Diagram B is an ion,
because the number of electrons does not equal the number of protons. Since there are more
electrons than protons, the ion is an anion, and has a net negative charge.
Diagram C is Lithium, because it has the atomic number 3. It is not an isotope, because
3P+4N=7, and 7 is the mass of a regular lithium atom (listed on the periodic table.) Diagram C is
a cation. There are more protons than electrons, which means that the ion has a net positive
charge.
4. Draw a neutral C atom, a C-14 isotope, and an O- ion.