A hypothesis represents an educated guess about what you think will happen, based on your observations. Before conducting an experiment, you propose a hypothesis so that you can determine whether your prediction is supported. There are several ways you can state a hypothesis. The best hypothesis is one you can test and easily refute.
An “If… then…because” statement in a hypothesis tells the readers what you believe will happen in an investigation when something is changed, so you can see the effect of the change.
Examples:
An “If… then…because” statement in a hypothesis tells the readers what you believe will happen in an investigation when something is changed, so you can see the effect of the change.
- IF…tells the readers what will be changed. This is the manipulated (independent) variable in the investigation.
- THEN… tells the reader what will happen because of the change (manipulated variable) described in the If… statement. This is the responding (dependent) variable in the investigation.
- BECAUSE… tells the reader how you know this will occur. It should be based on something you have experienced, or perhaps something you infer.
Examples:
- If 9th graders and 8th graders complete the same science problems, then the 9th graders will have more answers correct, because they have studied science for one year longer than the 8th graders.
- If dry bread and moist bread are left in bags for two weeks, then the moist bread will grow mold more quickly than the dry bread, because mold is a living organism, and organisms need water to survive.
- If some students eat breakfast before school and others do not, then the ones who do eat breakfast will have better grades in their morning classes, because their brains have more energy to think.
Scientific theories are hypotheses which have stood up to repeated attempts at falsification and are thus supported by a great deal of data and evidence. Some well known biological theories include the theory of evolution by natural selection, the cell theory (the idea that all organisms are made of cells), and the germ theory of disease (the idea that certain microbes cause certain diseases). The scientific community holds that a greater amount of evidence supports these ideas than contradicts them, and so they are referred to as theories. Theories can be disproved with new evidence.
Examples of scientific theories in different areas of science include:
Examples of scientific theories in different areas of science include:
- Astronomy: Big Bang Theory
- Biology: Cell Theory; Theory of Evolution; Germ Theory of Disease
- Chemistry: Atomic Theory; Kinetic Theory of Gases
- Physics: Theory of Relativity; Quantum Field Theory
- Earth Science: Giant Impact Theory; Plate Tectonics
Scientific laws are similar to scientific theories, in that they are principles which can be used to predict the behavior of the natural world. Both scientific laws and scientific theories are typically well-supported by observations and/or experimental evidence. Usually scientific laws provide rules for how nature will behave under certain conditions.
Examples of scientific theories in different areas of science include
Examples of scientific theories in different areas of science include
- Biology: Mendel's Law of Independent Assortment
- Chemistry: Boyle's Law
- Physics: Newton's Laws of Motion
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