What You Need to Know

Key Concept Diagram

The steps of the scientific method: observation, question, hypothesis, experiment, data collection, analysis, conclusion, communication

A hypothesis is a testable prediction, usually in the form "If..., then..., because..."

A controlled experiment changes one variable (independent) while keeping all others constant (controlled variables) and measures the outcome (dependent variable)

Scientific conclusions must be supported by evidence and may be revised if new evidence emerges

Key Vocabulary

Hypothesis

A testable, evidence-based prediction about the outcome of an investigation, often phrased as "If... then... because..."

Independent variable

The variable deliberately changed by the scientist in an experiment

Dependent variable

The variable measured or observed in an experiment — the outcome

Controlled variable

A variable kept constant throughout an experiment to ensure a fair test

Knowledge Check

Select the correct answer for each question. Click "Check Answer" to see if you are right.

Question 1

Which of the following is the best hypothesis for an experiment investigating how sunlight affects plant growth?

"If plants receive more sunlight, then they will grow taller, because light is needed for photosynthesis." "I think sunlight matters." "Plants need sunlight." "Sunlight is important for many reasons."

Question 2

In an experiment testing whether temperature affects the rate of yeast activity, what is the dependent variable?

The temperature The rate of yeast activity (bubbles produced) The amount of water used The type of yeast

Question 3

Why is it important to have controlled variables in an experiment?

To make the experiment easier to set up To test as many variables as possible at once To ensure that any change in the dependent variable is caused only by the independent variable Controlled variables are not actually important

Scientific Method