Scientific Method for High School Investigations Worksheet

Question 1

A student wants to investigate whether the amount of light affects the growth rate of bean plants. Write a testable scientific question for this investigation.

Accepted Answer

A testable scientific question is: How does the number of hours of light per day affect the height growth of bean plants over three weeks?

Question 2

For the bean plant investigation, write a hypothesis in if-then-because format.

Accepted Answer

If bean plants receive more hours of light each day, then they will grow taller because light provides energy for photosynthesis, which supports plant growth.

Question 3

In an experiment testing how water temperature affects the rate at which a sugar cube dissolves, identify the independent variable, dependent variable, and two controlled variables.

Accepted Answer

The independent variable is the water temperature. The dependent variable is the time it takes for the sugar cube to dissolve. Two controlled variables are the size of the sugar cube and the volume of water used in each trial.

Question 4

A student tests whether a new fertilizer improves tomato plant growth. One group of plants receives fertilizer, and another group receives no fertilizer. Explain the purpose of the no-fertilizer group.

Accepted Answer

The no-fertilizer group is the control group. It provides a baseline for comparison so the student can determine whether any difference in growth is likely due to the fertilizer.

Question 5

A lab group measures reaction time after students drink different amounts of caffeine. List two ways this investigation could be made more reliable.

Accepted Answer

The investigation could be made more reliable by using a larger sample size and repeating each trial multiple times. The group should also keep testing conditions the same, such as the reaction time test and the time after caffeine intake.

Question 6

A student claims that music improves memory because 8 students remembered more words while listening to music than while sitting in silence. Identify one possible source of bias or error in this conclusion.

Accepted Answer

One possible source of bias or error is the small sample size. Eight students may not represent the larger population, so the results may not be strong enough to support a broad conclusion.

Question 7

A class measures the effect of pH on enzyme activity. The data show enzyme activity is highest at pH 7 and lower at pH 4 and pH 10. Write a conclusion that is supported by the data.

Accepted Answer

The data support the conclusion that this enzyme works best near pH 7. Enzyme activity decreases in both more acidic and more basic conditions.

Question 8

A student writes: The chemical reacted faster because it was hotter. Revise this statement into a stronger scientific claim using specific variables.

Accepted Answer

A stronger claim is: Increasing the temperature of the reactants decreased the time required for the chemical reaction to finish, which means the reaction rate increased.

Question 9

A researcher records the following times for a cart to travel 2 meters: 1.25 s, 1.27 s, 1.26 s, and 1.89 s. Which value appears to be an outlier, and what should the researcher do before deciding whether to remove it?

Accepted Answer

The value 1.89 s appears to be an outlier because it is much higher than the other measurements. The researcher should check for recording errors, equipment problems, or procedural mistakes before deciding whether to remove it.

Question 10

Choose the best type of graph for showing how the temperature of a substance changes over time during heating. Explain your choice.

Accepted Answer

A line graph is the best choice because it shows how a continuous variable, temperature, changes over another continuous variable, time.

Question 11

A student wants to compare the effectiveness of three disinfectants at reducing bacterial growth on agar plates. Describe a fair experimental design with a control group.

Accepted Answer

The student should prepare identical agar plates with the same type and amount of bacteria. Three plates should receive equal amounts of different disinfectants, and a control plate should receive no disinfectant or sterile water. The plates should be kept under the same conditions and compared after the same amount of time.

Question 12

Explain why scientists repeat trials during an investigation instead of relying on one measurement.

Accepted Answer

Scientists repeat trials to reduce the effect of random error and to see whether results are consistent. Multiple trials make the average result more reliable than a single measurement.

Question 13

A thermometer consistently reads 2 degrees Celsius too high. Explain how this affects accuracy and precision.

Accepted Answer

The measurements may still be precise if they are close to one another, but they are not accurate because they are consistently above the true temperature by 2 degrees Celsius.

Question 14

A group wants to test whether exercise affects heart rate. Identify one ethical or safety concern and explain how the group should address it.

Accepted Answer

One safety concern is that some participants may have health conditions that make exercise risky. The group should use low to moderate activity, get permission when required, allow participants to stop at any time, and avoid testing anyone who should not exercise.

Question 15

Read this investigation summary: Students tested whether salt concentration affects the boiling point of water. They heated 100 mL of water with 0 g, 5 g, and 10 g of salt, measured boiling temperature once for each sample, and concluded that salt always raises boiling point. Evaluate the conclusion and suggest one improvement.

Accepted Answer

The conclusion is too broad because each salt concentration was tested only once, so random error could affect the results. One improvement is to run multiple trials for each salt concentration and calculate an average boiling point before making a conclusion.

Scientific Method for High School Investigations

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