THE SCIENTIFIC METHOD

What is the scientific method? Please open your textbook to page 378 The scientific method is a way to ask and

answer scientific questions by making observations and conducting experiments.

We will explore the scientific method step by step and discuss what actions need to be taken during each step.

Making Observations & Asking Questions

The scientific method begins with a question: how, what, when, where, who, which or why?

When choosing your question you must make sure it is something that can be measured. It is best if your measurements can be quantitative instead of qualitative.

Gathering Information & Identifying the Problem

Use a variety of resources to research your topic. There may already be an answer out there for your question!

Research will also help you learn about techniques and equipment that can help you carry out your experiment.

Stating a Hypothesis A hypothesis is an educated guess about

the outcome of your experiment. It will be based on your previous knowledge and the information you obtained during your research.

Your hypothesis should be stated in a way that can be easily measured and your research question can be answered.

Performing an experiment Design an experiment to test your hypothesis.

It should be designed so that you can collect relevant and fair data that can be used to prove (or disprove) your hypothesis.

In order to collect relevant data it is important that you only change one variable at a time while keeping all others constant. It is also a good idea to perform your test more than once.

What are variables? Variables are factors that may influence

the outcome of an experiment or investigation.

When you are planning and carrying out an experiment you must control all variables except for one. If not your data will not be relevant.

There are several types of variables you must consider during your experiment.

Independent Variable The variable that you change is known as

the independent variable. This is also known as the manipulated

variable. For example, if you were testing the effect

temperature has on a chemical reaction you would change the temperature several times to see if it has an effect.

Dependent Variable The variable that changes as a result of the

independent variable is known as the dependent variable.

It is often called the responding variable. This is the variable you will be measuring, or

the data you will collect.

How can I remember the difference? An easy way to remember the variables is that

the dependent variable depends on the independent variable.

In other words, as you change your independent variable it should have an effect on your dependent variable.

Control Variables Control variables are the variables that

must be kept constant throughout the experiment so that they do not have an affect on the dependent variable.

These are also known as standardizing variables.

If you do not control these variables your data will not be relevant.

Control Group Experiments often have a control group.

This is a group that has the independent variable eliminated or it is set at a standard value.

For example, if you were testing the effect of a new drug to treat headaches, you would have a test group taking the new drug and a control group taking no drug or a placebo.

Recording & Organizing Data

Once you have collected the data you need to organize it into tables.

Data should be processed and presented in a graph for analysis.

Analyzing & Presenting Data

Forming A Conclusion Once you have collected the data you

need to analyze your results and draw a conclusion about your hypothesis.

Did your experiment give you enough relevant data (proof) to answer your research question?

You may have found some error in your method and need to repeat your experiment again to collect relevant data.

Report your results Once you have completed your

experiment and drawn conclusions about your results it is time to write a report to communicate your results.

We will discuss how you will present your information in a lab report at a later time.

Expect the unexpected……… At any point during the scientific method

new information may cause you to rethink your hypothesis or the design of your experiment.

This can result in the repetition of one or many steps in the scientific method.

Identifying Variables You must be able to identify the independent,

dependent and control variables used in experiments.

The next few slides are examples of experiments and you will practice identifying each type of variable.

Example 1 A science student thinks that grade 10

students will perform better on the same Ecology quiz than grade 8 students.

IV DV CV

Answer A science student thinks that grade 10

students will perform better on the same Ecology quiz than grade 8 students.

IV grade level of student DV performance on test CV all students write the same quiz, study

same material

Example 2 A science student conducts an experiment to

test the effect of caffeine on reaction time. A group of 20 year old test subjects will consume 125 ml, 250 ml, or 500 ml of coffee and then perform a reaction time test.

IV DV CV

Answer A science student conducts an experiment to test the

effect of caffeine on reaction time. A group of 20 year old test subjects will consume 125 ml, 250 ml, or 500 ml of coffee and then perform a reaction time test.

IV amount of caffeine consumed DV reaction time CV age of test subjects, same reaction time test

Example 3 A science student thinks that listening to music

improves his ability to study. He conducts an experiment where half of his test subjects study while listening to music and the other half study without music. Each student writes the same test.

IV DV CV

Answer A science student thinks that listening to music

improves his ability to study. He conducts an experiment where half of his test subjects study while listening to music and the other half study without music. Each student writes the same test.

IV Studying with or without music DV How well the students perform on the test CV same test

Example 4 A science student is conducting an experiment to

test the solubility of sugar cubes in water of different temperatures. Sugar cubes were placed in water at 10°C, 20°C, and 30°C and the time it takes for them to dissolve was measured.

IV DV CV

Answer A science student is conducting an experiment to

test the solubility of sugar cubes in water of different temperatures. Sugar cubes were placed in water at 10°C, 20°C, and 30°C and the time it takes for them to dissolve was measured.

IV temperature of water DV rate at which the sugar cubes dissolve (time) CV sugar cubes, amount of water