A hypothesis is a testable statement that predicts the relationship between two variables; it is written before the experiment and later accepted or rejected on the evidence.
Malay: Hipotesis · Chinese: 假设
A hypothesis is a testable statement that predicts how one variable depends on another. It is written before the experiment is carried out and, once the data are analysed, it is either accepted or rejected. A well-written hypothesis names the manipulated variable and the responding variable and states the direction of the relationship between them, for example: “the higher the temperature, the faster the rate of reaction.” Because the SPM Chemistry syllabus (4541) treats scientific skills as examinable, you are often asked to state a hypothesis for a described experiment, and it must be a prediction you could actually test.
A good template to memorise is: “As the [manipulated variable] increases, the [responding variable] increases (or decreases).” Suppose an experiment investigates how the concentration of acid affects how quickly a gas is produced. A correct hypothesis is “the higher the concentration of the acid, the faster the gas is produced.” Notice that it links two measurable quantities and can be checked by experiment, that is what makes it testable rather than a vague guess. A statement that names only one variable, or that cannot be measured, is not a proper hypothesis and will not earn the mark.
A hypothesis can turn out to be wrong, and that is perfectly acceptable: if the data do not support it, you reject it and say so in the conclusion. The value of a hypothesis is not that it is always correct but that it is clear enough to be tested and either supported or rejected by evidence you collect yourself.
The confusion to avoid is between a hypothesis and an aim. The aim states the purpose of the experiment (“to investigate how concentration affects reaction rate”); the hypothesis predicts a relationship and can be proven right or wrong. Do not confuse it with a conclusion either, the conclusion comes after the data, whereas the hypothesis comes before.
Within this chapter the hypothesis sits at the heart of the scientific method and links directly to the three kinds of variable. Our teachers give you sentence frames so that stating a testable hypothesis becomes automatic.
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