How do scientists come up with new hypotheses or predictions? They follow a step-by-step process known as the scientific method. This method turns a spark of curiosity into an established theory through research, planning and experimentation.
Observation
The first step in the scientific method process is to observe something you wish to understand, learn from, or ask a question you would an answer to. This can be something general or as specific as you like.
Once you've decided on a topic, you will need to research it thoroughly using existing information. You can collect data from books, academic journals, textbooks, the internet and your own experiences. You could even carry out an informal experiment of your own!
Figure 1 - When researching your topic, use as many resources as possible to build a solid foundation of knowledge, unsplash.com
Suppose you want to know the factors that affect the rate of a chemical reaction. After some research, you've discovered that temperature influences the rate of chemical reactions.
Your simple question could be: 'How does temperature affect the rate of reaction?'
What is the Definition of a Hypothesis?
After researching your topic using existing data and knowledge, you will write a hypothesis. This statement should help to answer your simple question.
A hypothesis is an explanation that leads to a testable prediction. In other words, it is a possible answer to the simple question posed during the observation step that can also be tested.
Your hypothesis should be based on a robust scientific rationale supported by the background research conducted in the first step using the scientific method.
Is a theory the same as a hypothesis?
What differentiates a theory from a hypothesis is that a theory tends to address a broader question supported by a vast amount of research and data. A hypothesis (as mentioned above) is a potential explanation for a much smaller and more specific question.
If experiments repeatedly support a hypothesis, that hypothesis can become a theory. However, theories can never become indisputable facts. Evidence supports, not proves, theories.
Scientists don't claim that their findings are correct. Instead, they state that their evidence supports their hypothesis.
Evolution and the Big Bang are widely accepted theories but can never be truly proven.
An Example of a Hypothesis in Science
During the observation stage, you discovered that temperature could affect the rate of a chemical reaction. Further research determined that the rate of reaction is faster at higher temperatures. This is because molecules require energy to collide and react with each other. The more energy there is (i.e., the higher the temperature), molecules will collide and react more often.
A good hypothesis could be:
‘Higher temperatures increase the rate of reaction because the particles have more energy to collide and react.’
This hypothesis makes for a possible explanation that we would be able to test to either prove it correct or not.
What is the Definition of a Prediction?
Predictions assume that your hypothesis is true.
A prediction is an outcome that is expected if the hypothesis is true.
Prediction statements typically use the words ‘if’ or ‘then’.
When putting a prediction together, it should point towards a relationship between an independent and dependent variable. An independent variable stands alone and isn't affected by anything else, whereas, a dependent variable can change due to the independent variable.
An Example of Prediction in Science
As a continuation of the example we are using in this article. A good prediction could be:
'If temperatures are increased, then the rate of reaction will increase.'
Note how if and then are used to articulate the prediction.
The independent variable would be the temperature. Therefore the dependent variable is the rate of reaction - this is the outcome we are interested in, and it depends on the first part of the prediction (the independent variable).
The Relationship and Difference Between Hypothesis and Prediction
Hypothesis and prediction are two different things, but they are frequently confused.
Both are statements assumed to be true, based on existing theories and evidence. However, there are a couple of key differences to remember:
A hypothesis is a general statement of how you think the phenomenon works.
Meanwhile, your prediction shows how you will test your hypothesis.
The hypothesis should always be written before the prediction.
Remember that the prediction should prove the hypothesis to be correct.
Gathering Evidence to Test the Prediction
The purpose of an experiment is to gather evidence to test your prediction. Gather your apparatus, measuring equipment and a pen to keep track of your results!
When magnesium reacts with water, it forms magnesium hydroxide, Mg(OH)2. This compound is slightly alkaline. If you add an indicator solution to the water, it will change colour when magnesium hydroxide has been produced and the reaction is complete.
To test the reaction rate at different temperatures, heat beakers of water to the desired temperature, then add the indicator solution and the magnesium. Use a timer to track how long it takes for the water to change colour for each water temperature. The less time it takes for the water to change colour, the faster the rate of reaction.
Make sure to keep your control variables the same. The only thing you want to change is the temperature of the water.
Accepting or Rejecting the Hypothesis
The conclusion shows the results of the experiment - have you found evidence to support your prediction?
If your results match your prediction, you accept the hypothesis.
If your results don’t match your prediction, you reject the hypothesis.
You can’t prove your hypothesis, but you can say that your results support the hypothesis that you’ve made. If your evidence backs up your prediction, you are one step closer to figuring out if your hypothesis is true.
If the results of your experiment don't match your prediction or hypothesis, you shouldn't change them. Instead, reject your hypothesis and consider why your results didn't fit. Did you make any errors during your experiment? Did you make sure all the control variables were kept the same?
The less time it takes for the magnesium to react, the faster the rate of reaction.
| Temperature (ºC) | Time Taken for the Magnesium to React (seconds) |
| 10 | 279 |
| 30 | 154 |
| 50 | 25 |
| 70 | 13 |
| 90 | 6 |
Will you accept or reject the original hypothesis?
Remember that a hypothesis is an explanation for why something happens. The hypothesis is used to make the prediction - the outcome you would get if your hypothesis is true.
Hypothesis and Prediction - Key takeaways
- The scientific method is a step-by-step process: observation, hypothesis, prediction, experiment and conclusion.
- The first stage, observation, is researching your chosen topic.
- Next, you will write a hypothesis: an explanation that leads to a testable prediction.
- Then you will write a prediction: the expected outcome if your hypothesis is true.
- The experiment gathers evidence to test your prediction.
- If your results match your prediction, you can accept your hypothesis. Remember that acceptance doesn't mean proof.
1. CGP, GCSE AQA Combined Science Revision Guide, 2021
2. Jessie A. Key, Factors that Affect the Rate of Reactions, Introductory Chemistry - 1st Canadian Edition, 2014
3. Neil Campbell, Biology: A Global Approach Eleventh Edition, 2018
4. Paul Strode, The Global Epidemic of Confusing Hypotheses with Predictions Fixing an International Problem, Fairview High School, 2011
5. Science Made Simple, The Scientific Method, 2019
6. Trent University, Understanding Hypotheses and Predictions, 2022
7. University of Massachusetts, Effect of Temperature on the Reactivity of Magnesium in Water, 2011
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