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