Scientific Method

What is the scientific method?

• It is a way in which scientists answer and solve problems

• The steps to solve a problem or question

Steps of the scientific method

1. State problem or question to be solved or answered

2. Form a hypothesis3. Experiment to test hypothesis4. Collect data from experiment and observations5. Form a conclusion6. Communicate ideas and results

Use observations to form a question you would like to investigate

• You can use your senses to gather information. – _______________ observation

• You can use tools to gather information called measurements– _______________observation– Tools make accurate observations.

• Often you are asking a question about the relationship between things

• Example: The position of the light source and the size of the shadow

Qualitative

Quantitative

Hypothesis

• A possible explanation that needs to be tested

• “If…….., then………. will happen. • Form a hypothesis about the position of the light source

on the object and the length of the object’s shadow.

• Hypotheses are NOT facts! Instead it is a possible way to answer a question.

• Many trials are needed before a hypothesis can be accepted as true.

If the light source gets closer to the object, then the objects’ shadow will get…

Experiment

• When you carry out procedures to test your hypothesis• Experiments begin by first examining all the variables• Variables are factors that can change in an experiment – Can you name a few variables that could change in an

experiment? • Experiments should be designed so only one variable is

changed!• There are two types of variables: Independent variable

and dependent variable

Independent Variable

• The variable that is changed in an experiment– Example: Susan sets up an experiment to test

whether the position of the light impacts the length of the shadow. In order to test this, she shines the light on a cereal box from six different positions. At each position, she measures the length of shadow the cereal box casts. What would be the independent variable? (Hint what is Susan changing?)

The position of the light

Dependent Variable

• The variable that is expected to change because of the independent variable. – Example: Think about Susan’s experiment to test

whether the position of the light impacts the length of the shadow. She shown the light on a cereal box from six different positions, and at each position, she measured the length of shadow the cereal box casts. What is the Dependent variable? (Hint: what is changing because of Susan’s independent variable?)The length of the shadow

Identify the Dependent and Independent Variables.

• Students conduct an experiment to test if studying leads to higher tests scores. What would be the independent variable (the thing that changes)? What would be the dependent variable (What is changing because of the independent variable)?

Independent Variable: Time spent studying

Dependent Variable: Test score

Identify the Independent and dependent variable

• A scientist conducts an experiment to test the theory that a vitamin could extend a person’s life-expectancy– What would be the independent variable?– What would be the dependent variable?

Independent Variable: Taking Vitamins

Dependent Variable: Life-expectancy (How long you live)

Identify the independent and dependent variables.

• Students experiment to see how different amounts of sunlight impact how much plants grow.– What would be the independent variable?– What would be the dependent variable?

Independent Variable: Amount of sunlight

Dependent Variable: Plant growth

Control Group and Experimental Group• A control group is a group in a scientific

experiment where no variables are changed.• It is used to compare results against the a

group where a variable is changed called an experimental group. – Example- A student is testing to see if plants will

grow without sunlight. • Which would be the experimental group and which

would be the control group?

Control Experimental

What makes a good experiment:

• Control group• One independent variable• Testing the hypothesis many times (many

trials)

Collecting and Interpreting Data

• Make observations and record them into a data table.

• Data tables can be for both quantitative and qualitative observations. – Make a data table that would describe some qualitative

observations of different types of rocks– Make a data table that would describe some

quantitative observations of different types of rocks.• Graphs are useful way to view quantitative data

because they reveal trends or patterns

Explain the graph

Explain the graph

Explain the graph

Drawing Conclusions

• After scientists interpret their data (with the help of a graph usually), they draw a conclusion about their hypothesis.

• Conclusions state whether or not the data supports the hypothesis– My hypothesis was correct because….– My hypothesis was incorrect because…

Should be supported by observations!!!

Communicating

• Sharing ideas and conclusions about your experiment with others through writing and speaking

• Scientists share the design of an experiment as well so others can repeat the experiment to check the results

• Communicating information about discoveries often leads to new questions, new hypotheses, and new investigations.

Model

• Represents an object or system in science. – Example: Globe of Earth

Theory• A well tested explanation for many observations

and experimental results. • Well tested and widely accepted by scientists.– Example: Atomic theory- all substances are composed

of tiny particles called atoms. This theory explains many observations: why water freezes or boils at certain temperature, and why water can dissolve many other materials

Law• A statement that describes what scientists

expect to happen every time under a particular set of conditions– Example- Law of Gravity “What goes up must

come down.” • A scientific law describes an observed pattern

in nature without attempting to explain it.