Step by Step
Maya reads books and reliable websites about how plants grow before designing her experiment. Which scientific method step is she doing?
Research.
Which question can be answered by measuring melting time: “Which ice cube shape is prettiest?” or “Which ice cube shape melts fastest?”
“Which ice cube shape melts fastest?” Compare equal masses of ice at the same starting temperature and under the same surrounding conditions.
What do we call the conditions that we keep the same during an experiment?
Constants or controlled variables.
What do we call the observations and measurements collected during an investigation?
Data.
A group presents its investigation to the class. Which scientific method step is this?
Communicate.
Leo follows his procedure, tests his paper airplanes, and records their flight distances. Which step is he doing?
Experiment.
What is the difference between a hypothesis and a prediction?
A hypothesis is a proposed, testable explanation or answer to a scientific question. A prediction states the result you expect if that hypothesis is supported.
A student tests how ramp height affects how far a toy car rolls. Identify the independent variable and explain why it is independent.
Ramp height is the independent variable because the student deliberately changes it to test its effect on rolling distance.
Which is a more useful scientific observation: “The mixture looked weird” or “Small bubbles formed for 20 seconds”? Explain why.
“Small bubbles formed for 20 seconds.” It describes something specific that was observed and includes a measurement of time.
What should you use to support a scientific conclusion: your preferred outcome or your collected data?
Collected data. A conclusion should be supported by evidence.
Ava compares her measurements and looks for patterns. Which step is she doing?
Analyze.
How does background research make a hypothesis stronger?
It helps scientists develop a reasonable, testable explanation based on what is already known and make a prediction from it.
A class compares how much water different paper towel brands absorb. Identify the dependent variable and a suitable unit for measuring it.
The amount of water absorbed is the dependent variable. Measure its volume in milliliters (mL).
Also acceptable: the mass of absorbed water in grams (g), measured by subtracting the towel’s dry mass from its wet mass.
A toy car rolls 55 cm when a ramp’s starting height is 10 cm, 84 cm when it is 20 cm, and 112 cm when it is 30 cm. Describe the pattern using two measurements as evidence.
In these trials, greater starting heights are associated with longer rolling distances. For example, the car rolls 55 cm at a 10 cm height and 112 cm at a 30 cm height.
Another correct pair of measurements is acceptable. These data alone do not show whether all other conditions were controlled.
Your results do not support your hypothesis. Does that automatically mean your experiment failed? Explain.
No. A carefully conducted experiment can provide useful evidence even when the prediction is not supported. Report what the data show.
What is the difference between planning an experiment and carrying it out?
Planning means deciding on the materials, procedure, measurements, and fair-test conditions. Carrying it out means following the procedure and collecting data.
Rewrite “Which paper airplane is best?” as a testable question. Say what you would measure.
Example: “Which paper airplane design travels the farthest?” Measure flight distance in meters or centimeters.
Other measurable comparisons, such as flight time in seconds, are also acceptable.
A student uses a heavy toy car on a high ramp and a light toy car on a low ramp. Why can’t they tell whether ramp height caused a difference in travel distance?
Both the car and the ramp height changed. They should use the same car while changing only the ramp height.
A ball bounces 21 cm, 23 cm, and 22 cm in three trials under the same conditions. What is its average bounce height, and why use several trials?
The mean is 22 cm: (21 + 23 + 22) ÷ 3.
Several trials help reveal variation and check consistency. Averaging can reduce the effect of random variation, but repeating a consistently flawed measurement method will not fix that method.
When sharing an experiment, why should you include your materials and procedure as well as your results?
Other people need those details to understand how the evidence was collected, evaluate the test, and repeat the investigation.
Put these steps in the order shown in your worksheet: Communicate, Experiment, Question, Conclude, Hypothesize, Analyze, Research, Plan. Then give one reason a scientist might return to an earlier step.
Question → Research → Hypothesize → Plan → Experiment → Analyze → Conclude → Communicate.
Example: Unexpected results might lead a scientist to do more research, revise a hypothesis, or improve the procedure.
Research suggests that moving air can speed evaporation. Write an “If…then…because…” statement comparing matching towels with equal starting amounts of water, drying with and without a fan. What would you measure?
Example: If a wet towel is exposed to a fan, then it will dry in less time than a matching towel without a fan because moving air carries away water vapor near its surface, helping evaporation continue.
Measure drying time in minutes, using the same definition of “dry” for both towels. Another option is water mass lost in grams over the same time period.
Design a fair test of which paper towel brand absorbs the most water per equal-sized sample. Identify the independent variable, dependent variable, and two controlled variables. How would you check whether the results are consistent?
Independent variable: brand.
Dependent variable: water absorbed (mL or g).
Controlled variables: any two, such as sample area, number of whole sheets, starting water volume, soaking time, draining time, or water temperature.
Repeat the test several times for each brand with fresh samples and compare results. Use enough water that the supply does not limit absorption. Differences in product construction are part of the brand comparison.
A ball’s bounce heights are 28, 30, 29, and 85 cm under supposedly identical conditions. What should the scientist do about the unusual result?
Keep the original data, check for measurement or procedure errors, and repeat trials under the same conditions.
Do not erase the result just because it is different; document any confirmed error and how it is handled.
Three groups of the same plant species start at similar heights and grow under the same conditions except for daily watering: 10, 20, or 30 mL per plant. Their mean height increases after two weeks are 2, 5, and 3 cm, respectively. Do these data support “More water always means more height growth”? Use two measurements and limit your conclusion to this experiment.
No. The 20 mL group grows an average of 5 cm, while the 30 mL group grows only 3 cm.
In this experiment, more water does not always correspond to greater height growth; the 20 mL group has the greatest mean growth among the amounts tested. This does not establish a best watering amount for every plant or condition.