The Scientific Method

Steps

2. Research

3. Hypothesis

4. Perform Experiment and/or collect data

6. Write a scientific explanation/argument

1. Observe a phenomena, which leads to a question

5. Organize and analyze data (this is your evidence!)

In an experiment the independent variable is the variable that is changed on purpose by the scientist.

Only the results of a well-designed experiment can be considered accurate and trustworthy. A well-designed

experiment has 4 main components: an independent variable, a dependent variable, constants and a control group

The dependent variable is the response to the independent variable that is measured. The scientist focuses his or her observations on the dependent variable to see how it responds to the change made to the independent variable.

Lets consider an example. We are going to design an experiment to test whether

the color of light that plants are exposed to affects how quickly the plants grow. We set up four stations, each with a different

color (red, blue, green, and natural sunlight) of light shining on the plants. We

measure the plants’ growth daily for 3 weeks and record our measurements.

Dependent variable: amount of plant growth (height)

Independent variable: the color of light

Experiments also have constants. Constants are the parts of an experiment that a scientist wants to remain the same from trial to trial, and he/she must observe them carefully!!

Constants: type of soil, amount of water, time spent under the light, type of plant, same fertilizer……..

Some, but not all, experiments also use a control group. The control group is not exposed or treated with the “special” independent variable. It is considered the “normal situation”.

Control: natural sunlight

Maria and Elena are supposed to help their mom chill some soda by putting the cans into a bucket filled with ice cubes, but Maria forgot to fill the ice cube trays. Elena says that she remembers reading somewhere that the hotter the water is, the faster it will freeze. Maria is skeptical, so the girls decide to conduct a scientific experiment to determine whether it is faster to make ice cubes with hot water, cold water, or room temperature water.

Question:

Independent Variable:

Dependent Variable:

Control Group:

Constants:

Does it take hot, cold, or room temperature water longer to freeze?

Starting temperature of the water

Time it takes the water to freeze

same freezer, same source of water, same location in the freezer, ice cube trays

made of the same material, same amount of water, same starting temperature of the ice cube tray.

Room temperature water