Variables, Variables Everywhere!
What do we call the factor that a scientist changes on purpose in an experiment?
Independent variable (test variable)
True or False: A statement predicting what will happen in an experiment is called a hypothesis.
True
What does it mean when an experiment is replicable?
Other scientists can repeat it and get the same or similar results
True or False: All scientific investigations are experiments.
False
What do scientists use as the basis for their explanations?
Evidence or data
What you measure and observe to see how it changes in response to the testing variable?
Dependent variable (outcome variable)
Identify whether this is a hypothesis or not: “If I water my plants every day, then they will grow taller than plants I don’t water.”
Hypothesis
Which describes a repeated observation about the natural world: a law or a theory?
Law
What 3 things makes an investigation an experiment?
It involves (Independent) testing variables, controlling conditions, and observing outcomes(dependent variables)
Why is evidence and data important in science?
It supports claims and explanations, showing that conclusions are based on observations and data
In an experiment to test if plants grow taller with more sunlight, what is a control variable that should stay the same?
Things like the type of plant, amount of water, type of soil, or size of the pot
A student writes: “Plants grow faster in blue light than red light because blue light is more energizing.” Is this a hypothesis? Explain why or why not.
Yes; it is a testable prediction with reasoning that can be tested in an experiment
If two scientists do the same experiment and get different results, what should happen next?
The experiment should be repeated carefully to check for errors or differences in conditions
A student observes animals in the wild without changing anything. Is this an experiment or another kind of investigation?
Another kind of investigation (observational study)
A student claims fertilizer makes plants grow taller. What hypothesis would support this claim? (is/then)
If plants gets fertilizer then they will grow taller than plants without fertilizer under controlled conditions.
In an experiment to test if plants grow taller with more sunlight, what is the dependent variable?
Plant height
A student observes that plants near a window grow taller than plants in a dark corner. They write: “Plants grow taller because of sunlight.” Is this a hypothesis? Explain why or why not.
No; it is an observation or conclusion, not a testable prediction. A proper hypothesis would be: “If plants are exposed to sunlight, then they will grow taller than plants in the dark,” which predicts an outcome that can be tested.
True or False: A scientific law explains why something happens.
False (laws describe what happens, not why)
A geologist studies rock layers to explain Earth’s history. Is this an experiment or not? Explain.
Not an experiment; it is an observational investigation because variables aren’t being manipulated
Two students test the same question but collect different evidence. One claims fertilizer helps plants, the other says it doesn’t. What should they do next?
Compare methods, repeat experiments, and collect more evidence to see which explanation is supported most reliably.
A student tests if the temperature of water affects how fast sugar dissolves. He conducts the test in 3 identical cups with the same amount of water and same amount of sugar. Identify the independent and dependent variables. as well as the control.
Independent variable = water temperature;
Dependent variable = rate at which sugar dissolves
Control = identical cups, water and sugar.
A student notices that their cat seems more active in the morning than at night. They write: “My cat is more active in the morning.” Is this a hypothesis? Explain why or why not.
No; this is an observation, not a testable prediction. A proper hypothesis would be: “If I observe my cat in the morning and at night, then it will be more active in the morning than at night,” which predicts an outcome that can be tested.
A student notices that every time they push a toy car, it rolls forward. They also try to explain why it moves differently on carpet versus a smooth floor. Which part of their observations is a law, and which part is a theory?
The consistent rolling forward when pushed is the______
The explanation about why it moves differently on different surfaces is the _______
The consistent rolling forward when pushed is the law (it describes what happens).
The explanation about why it moves differently on different surfaces is the theory (it explains the cause behind the observation).
DAILY DOUBLE ------
A scientist wants to test a new medicine. Explain why simply giving it to patients and recording what happens may not count as a proper experiment.
Because there are no controlled variables or comparison groups (like a placebo group); without controls, you can’t be sure the results are due to the medicine itself.
A new telescope finds data that challenges an old explanation about how planets form. What does this tell us about scientific explanations?
Scientific explanations can change when new evidence is discovered; science is always open to revision as knowledge grows.