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Thinking and Working Scientifically & Laboratory Reference

TWS 1: Asking Scientific Questions — Hypotheses, Variables & Fair Testing

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TWS 1: Asking Scientific Questions — Hypotheses, Variables & Fair Testing — Alhussan International Academy — Science (Stages 7–9) notes: Write a testable hypothesis and prediction, identify independent, dependent and control variables, choose a type of investigation and design a …

  • Questions science cannot answer
  • Part of predicting
  • Conclusion
  • Making a model
  • Field study
  • Survey or regular observations

Part 1 of 5What makes a question scientific

1Scientific question1 point
= a question that can be answered by collecting and thinking about data, where data are numbers from measurements or words from observations.
  • "How do fossil fuels form?" and "Why are there so many different animals on Earth?" are scientific questions.
2Questions science cannot answer2 points
— opinion questions, or questions whose answer does not depend on data.
  • Science can show which phone battery lasts longest or which phone accesses web pages fastest.
  • It cannot show which phone is best, because people value different things such as a big screen, a good camera or a tough case.

Part 2 of 5Hypotheses and predictions

  • Hypothesis a scientific theory or proposed explanation made on the basis of evidence that can be tested further.
  • Prediction what you think will happen in the future, based on the hypothesis.
  • Testablea hypothesis is testable if you can write a prediction from it and collect data to see whether the prediction is correct.
  • Part of predictingthink about what would happen if the hypothesis is wrong, so the investigation can show the difference between a correct and an incorrect hypothesis.
  • Conclusionit says whether the evidence supports or does not support the hypothesis.

Part 3 of 5Types of investigation

  • Fair testone variable is changed and all others are kept the same.
  • Making a modela model helps to answer a question and can also predict or explain.
  • Field studyan investigation of plants or animals in their natural habitat.
  • Survey or regular observationsmany observations or measurements taken over time or in different places.

Part 4 of 5Variables and fair testing

  • Variable = anything that might change during an experiment.
  • Independent variable — the quantity you deliberately change.
  • Dependent variable — the quantity that changes as a result and is measured.
  • Control variables — all the other quantities, kept the same.
  • Fair test — only the independent variable is changed, so any effect on the dependent variable is caused by it.
    • If two or more things change together, the cause of the result cannot be known.
  • Example variables — for the effect of temperature on dissolving, temperature is independent, time to dissolve is dependent, and mass of sugar, volume of water and stirring are controlled.

Part 5 of 5Models, field studies and secondary data

1Model2 points
— used when a practical investigation is not possible because the subject is too big, too small or too dangerous.
  • A physical model suits very large or small systems, such as a model of the Earth and Sun for day and night.
  • A computer model uses a computer program to find answers.
2Field study
— observations must be made without affecting what is being observed.
3Survey or regular observations1 point
— they may be made over a long time or at the same time in different locations.
  • A scientist may use secondary data collected earlier by other scientists.
4Matching
— a question about what chimpanzees eat is answered by many observations in their habitat, and which country uses most fuel by comparing collected data.

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