Lesson focus: Science begins with curiosity, but safe and useful science needs a methodThe step-by-step instructions for how an investigation is carried out..
Identify the purpose of a scientific investigation and explain why safety is part of good science.
You will be successful when you can…
- Tell the difference between an observation and an explanation.
- Put the main stages of an investigation in order.
- Explain why a method must be safe, clear and easy to repeat.
- Write a conclusion that uses the results and does not claim too much.
Words that carry the science
- observation
- Something you notice or measure, using your senses or equipment.
- inference
- An idea you work out from what you observed. You did not see it directly.
- hypothesis
- An idea that explains something and can be tested.
- evidence
- Observations or measurements that help show whether an idea is right.
- method
- The steps you follow, in order, to collect your results.
- conclusion
- Your answer to the question, using your results as evidence.
Turn curiosity into trustworthy evidence
01Begin with what is observed
An observationSomething you notice using your senses or measure with equipment, such as a colour change or a temperature. is what you notice or measure, such as “the tablet fizzed for 42 seconds”. An explanation says *why* it happened. Keep them separate, so a guess is not written down as if it were a fact.
Next, ask a clear question that evidenceObservations or measurements used to show whether an idea is right or wrong. can answer. A hypothesisA possible explanation for something you have noticed, which you can test. is an idea that explains something and can be tested. It leads to a predictionWhat you think will happen, and why, before you do the test.: what you expect to happen.
02Collect evidence through a method
A methodThe step-by-step instructions for how an investigation is carried out. is the list of steps you follow, in order. A clear methodThe step-by-step instructions for how an investigation is carried out. says what equipment to use, what to change, what to measure and how to stay safe.
If the method is clear, someone else knows exactly what to do. They can repeatDoing the same measurement again in the same way, to check how close the results are. it (do it again in the same way) and check whether they get similar results.
Safety is part of good science. If someone gets hurt or something spills, people are harmed and the results may be spoiled too.
03Conclude using the evidence
A conclusionA statement that answers the question you were investigating, using your results as evidence. is your answer to the question. A good conclusionA statement that answers the question you were investigating, using your results as evidence. uses the results as evidenceObservations or measurements used to show whether an idea is right or wrong.: “In our test, the plant in bright light grew 3 cm more than the plant in dim light.” A conclusion that ignores the results is just a guess, so nobody can trust it.
Results are only useful if they help answer the question you asked. Do not claim too much: one small investigation shows what happened in *your* test, not what *always* happens.
You need both. A clear method lets people trust how the results were collected. A conclusion that uses the results lets people trust what you say they show.
Each stage has a different job in building an evidence-based answer.
- ObserveNotice or measure something.
- QuestionAsk what you want to find out.
- PredictSay what you expect to happen, and why.
- InvestigateFollow a safe method to collect results.
- ConcludeAnswer the question using the results.
Separate observation from explanation
A student stirs some powder into water and says, “The powder disappeared because it was destroyed.”
- Find the observationSomething you notice using your senses or measure with equipment, such as a colour change or a temperature. (what they saw): the powder could not be seen after stirring.
- Find the explanation (why they think it happened): “it was destroyed”. They did not see this.
- Think of a way to test it: weigh the water and powder before and after, or let the water evaporate and see if powder is left.
- Write a hypothesis that can be tested: the powder may have dissolved, so it is still there in the water.
How to make the reasoning visible: Say what you actually saw first. Then say which idea still needs evidence.
Build an investigation story
Each statement below comes from one investigation about plants and light. Read which stage of the investigation each one is.
| Statement | Stage |
|---|---|
| Plant A grew 3 cm in seven days. | Observation/result |
| Does light intensity affect growth? | Question |
| Plants in brighter light will grow more because photosynthesis may be faster. | Prediction with reason |
| Measure height every day using the same ruler position. | Method |
| In this investigation, the brighter-light plant grew more. | Conclusion |
Look at the last row of the table: “In this investigation, the brighter-light plant grew more.” Why is this better than saying “bright light always makes every plant grow faster”?
Add one safety step to the method. (A safety step is something you do to stop someone getting hurt.)
In the table, which statement is the question and which is the predictionWhat you think will happen, and why, before you do the test.? How can you tell them apart?
Check your understanding
Answer from memory, then check against the suggested answer.
What is an observation?
What is a hypothesis?
What is a method?
What is a conclusion?
What is evidence?
What is the difference between an observation and an explanation?
A metal gate squeaks. After oil is put on the hinge, it squeaks less. (a) Write one observation. (b) Write a question you could test.
A student does an investigation three times and gets the same results each time. But the results do not answer the question they asked. Why is this still a problem?
A student writes the conclusion before doing the experiment. Why is this a problem?
Exam Question Practice
Exam Question Practice
Mark points shown after marking
Maya tests whether light affects how much a plant grows. She writes a method (the steps she follows) and a conclusion (her answer to the question). Answer the parts below to explain why she needs both.
What is a method?
(1)Maya’s method is clear. Why does a clear method help someone else? Start: “A clear method tells someone else exactly what to do, so they can …”
(1)Maya’s conclusion uses her results. Why is this important? Start: “Using the results means the conclusion is …”
(1)Total for this question: 3 marks
Command word: An explainA command word: say how or why something happens, giving reasons with words like "because" or "so". answer says what something does and why it matters. Joining words such as “so” and “because” help you do both.