The scientific method

The steps of the scientific method are out of order: experimentation, observation, conclusions and hypothesis. Write them in the correct order and explain in one sentence what is done in each step.

Match each stage of the scientific method with what is done in it:

1. a) Observation
2. b) Hypothesis
3. c) Experimentation
4. d) Conclusions

1) A possible explanation for what happens is proposed.

2) An event is carefully observed and recorded.

3) The results are compared with the initial idea.

4) A test is designed and carried out to check the idea.

State whether each sentence is an observation or a hypothesis:

1. a) "This morning the playground was wet."
2. b) "I think it rained overnight."
3. c) "The swimming pool water is at $24\ ^\circ\text{C}$."
4. d) "If I leave my bike outside when it rains, it will rust faster."

Classify these statements into "scientific hypotheses" (can be tested with an experiment) or "non-scientific", and justify one from each group:

1. a) "On Fridays I have bad luck in exams."
2. b) "A new ball bounces more than an old ball."
3. c) "Salt water boils at a higher temperature than plain water."
4. d) "Black cats bring bad luck."

You want to find out whether an egg floats more easily in very salty water than in salt-free water. Observe the setup in the figure:

Write down:

1. a) Your hypothesis.
2. b) The variable you change.
3. c) The variable you observe or measure.
4. d) Two things that must be kept the same in both glasses.

To find out whether light affects plant growth, Chloe places a pot with new soil on the window sill and another with old soil in a cupboard.

1. a) Will she be able to tell if light has an effect?
2. b) Explain the mistake she made.
3. c) How would you correct it?

You want to test whether water temperature affects the rate at which sugar dissolves. Design a complete experiment indicating:

1. a) The hypothesis.
2. b) The variable you will change (independent) and the one you will measure (dependent).
3. c) Two variables you will keep the same (control variables).
4. d) The steps you would follow and the expected result if your hypothesis is correct.

Leo wants to know whether a drink cools down faster in the fridge or in the freezer. He puts a large bottle of soft drink in the fridge and a small can in the freezer, and measures the time each takes to reach $8\ ^\circ\text{C}$.

1. a) Point out the flaws in the design.
2. b) Redesign the experiment so that it is a fair test.
3. c) Explain why only one factor at a time should be changed in an experiment.

Izan repeats the same experiment three times and measures the time it takes for an ice cube to melt: $8$ minutes, $8,5$ minutes and $20$ minutes.

1. a) Which value seems suspicious? Why?
2. b) What should Izan do with that data point before drawing conclusions?
3. c) Explain why experiments are repeated multiple times in science.

Martina is certain that, if dropped at the same time from the same height, a heavy ball always hits the ground before a light one. However, when she drops a basketball and a tennis ball, they both land at almost the same time.

1. a) Explain what a scientist should do when the results do not support their hypothesis.
2. b) Write a new hypothesis that Martina could test now.

"If I wear my lucky shirt, my team wins."

1. a) Explain why this statement, as it is worded, is not a good scientific hypothesis.
2. b) Rewrite a similar statement that can be tested with an experiment.
3. c) Briefly describe how you would test it.

An advertisement claims: "CrecePlus fertiliser makes plants grow twice as fast".

1. a) What experiment would you want to see to believe the advertisement? Describe the control group, what would be measured, and for how long.
2. b) Explain why a photo of a giant plant is not sufficient.