Scientific Method

The scientific method is a universal approach to scientific problems. The scientific method can be broken up into 5 main steps.

Problem 1.Problem – the question that you are trying to answer – This should be in the form of a question.

Hypothesis 2. Hypothesis – A prediction of what you think might happen in the experiment. – A hypothesis should be written in If…then form

Procedure 3. Procedure – the scientist must test a hypothesis by designing experiments that will either verify or disprove the predictions of the hypothesis

Observations/Data 4. Observations/Data – every experiment must include observations and data/measurements

Conclusion 5. Conclusion – a scientist must conclude their experiment by supporting or rejecting their hypothesis

Two things that are often done after an experiment: 1.Run the experiment again (several times) To test validity 2.Publish your results in a scientific journal

Control Group Control group – the set-up in which no change was made It serves as a reference to compare back to.

Experimental Group Experimental group – the set-up in which one factor is changed or tested This factor is called a variable. Variable – the single factor that is changed in an experiment

Constant Constant – something that stays the same in all groups of the experiment All the items in the control group and experimental group should remain constant EXCEPT the variable.

Does gasoline help plants grow? Control Group Sunflower plant Flower pot Sunlight Room temperature Soil Water Experimental Group Sunflower plant Flower pot Sunlight Room temperature Soil Gasoline

Dependent/Independent Variables Independent – you CAN control Dependent – you CANNOT control

Can you pick out the variables? 1.The number of red blood cells in a mouse’s blood at different levels of iron in its diet. Independent = different levels of iron Dependent = number of red blood cells

Can you pick out the variables? 2. A plant is exposed to light for different amounts of time which leads to different amounts of starch formed. Independent = different amounts of time Dependent = different amounts of starch formed

Can you pick out the variables? 3. The height of growth in a bean plant for different amounts of water. Independent = different amounts of water Dependent = height of growth

Theory vs. Law Theory – a statement designed to explain a set of observations that is supported by experimental evidence Scientific Law – a statement that expresses a principle of science that is always true A law does not explain how or why something occurs, just that it occurs