1.3 - Scientific Method and Communication_May

1.3 - Scientific Method and Communication

Lesson Objectives

• Identify the importance of asking questions.
• Explain how the steps of the scientific method are used to answer questions.
• Explain how scientists communicate with other scientists.
• Describe how scientific theories, laws, and models are created.

Vocabulary

• scientific method
• hypothesis
• scientific theory
• experiment
• independent variable
• dependent variable
• constants
• control group
• experimental group
• scientific model
• investigation
• scientific law
• scientific journal

Introduction

At sometime in your life you have asked a question about the world around you.  You have probably asked a lot of questions over the years.  The best way to answer questions about the natural world is by using science.  Scientists ask questions every day and use a set of steps to answer those questions.  These steps are known as the scientific method.  By following the scientific method, scientists can develop explanations about what occurs in the natural world.  As a scientist, you need to be curious, make keen observations, communicate with others, and consider the world around you.  You also need to wonder, observe, talk, and think.  Everything we learn leads to asking new and better questions.

Scientific Method

The scientific method is a process that uses a set of skills to answer questions or to test ideas about the natural world.  The series of steps used in each investigation often varies.  As we test our ideas, we may come up with more questions.  The basic sequence of steps followed in the scientific method is illustrated below.

The Scientific Method.

Questions

Asking a question is one really good way to begin to learn about the natural world.  You might have seen something that makes you curious.  You might want to know what to change to produce a better result.  Let’s say a farmer is having an erosion problem. She wants to keep more soil on her farm.  The farmer learns that a farming method called “no-till farming” allows farmers to plant seeds without plowing the land.  She wonders if planting seeds without plowing will reduce the erosion problem and help keep more soil on her farmland.  Her question is this: “Will using the no-till method of farming help me to lose less soil on my farm?”

Soil is often lost from ground that has been plowed.

Research

Before she begins, the farmer needs to learn more about this farming method. She can conduct research by reading books, magazines, or searching online publications. Another good way for her to gather information is to discuss it with people who have tried this method of farming. She can use all of this information to decide how she is going to test her question about no-till farming.

Rather than breaking up soil like in this picture, the farmer could try no-till farming methods.

Hypothesis

After conducting background research, the farmer will formulate a possible answer to the question.  She might think, “If I don’t plow my fields, then I will lose less soil than if I do plow the fields.  Plowing disrupts the soil and breaks up roots that help hold soil in place.”  This potential answer to her original question is her hypothesis.  A hypothesis is a possible explanation that can be tested.   Once she has a hypothesis, the next step is to complete experiments to test the hypothesis.  A hypothesis can be supported or not supported by testing.  If a hypothesis is repeatedly tested and shown to be true, then scientists call it a scientific theory.

Experiment

When we design experiments, we typically choose to change only one factor.  The independent variable, sometimes called the manipulated variable, is the factor that you want to test.  It is manipulated by the investigator to observe how it impacts a dependent variable. In the example, the farmer chooses two fields and then changes only one factor between the two fields. She changes how she plows her fields.  One field will be tilled and one will not be tilled.  The field that is being tilled is the experimental group.  The experimental group of an experiment receives the treatment.  The field that will not be tilled is the control group.  The control group of an experiment is used for comparison. Everything else will be the same on both fields: the type of crop she grows, the amount of water and fertilizer that she uses, and the slope of the fields she plants.  The fields should also be facing the same direction so they receive the same amount of sunlight each day.  These are the constants.  Constants are factors that must be kept the same throughout the experiment so that they do not affect the outcome.  If the farmer only changes how she plows her fields, she can see the impact of that one change.  After the experiment is complete, scientists then measure the result.  The farmer measures how much soil is lost from each field. This is the dependent variable, also called the responding variable.  How much soil is lost from each field “depends” on the plowing method.  The dependent variable is the factor that is observed or measured during the experiment.  

A pair of farmers take careful measurements in the field.

Investigations
Earth scientists cannot always control the aspects of an experiment.  It would be impossible to control the rainfall or temperature when studying the effects of a new fertilizer on thousands of acres of corn.  When this is the case, scientists refer to their research as an investigation.  An investigation involves observation and collecting data but does not include a control.  Investigations can often lead scientists to design future experiments based on the observations they have made.

Data and Experimental Error

During an experiment, a scientist collects data. The data might be measurements (quantitative data) or observations (qualitative data).  The scientist should record the data. At the end of the experiment the scientist analyzes the data. The scientist may create a graph or drawing to share the data.  These can make it easier to identify trends or patterns.  

Even in ideal circumstances errors do occur during experiments. Errors can occur as a result of inaccurate equipment, human error, or even flaws in experimental design. To avoid inaccurate data, the scientist should conduct the experiment many times and make many measurements or observations. By taking the average of many measurements the data is more likely to be accurate. Sometimes the result from one experiment is very different from the other results. If one data point is really different, it may be thrown out. It is likely a mistake was made in that experiment.

Conclusions

The scientist must next form a conclusion. The scientist must study all of the data. What statement best explains the data? Did the experiment support the hypothesis? Sometimes an experiment shows that a hypothesis is correct. Other times the data does not support the hypothesis. Sometimes it is not possible to tell. If there is no conclusion, the scientist may test the hypothesis again. This time different experiments would be used. No matter what the experiment shows the scientist has learned something. Even an unsupported hypothesis can lead to new questions.

The farmer grows crops on the two fields for a season. She finds that 2.2 times as much soil was lost on the plowed field as compared to the unplowed field. She concludes that her hypothesis was correct.  Her hypothesis was, "If I don’t plow my fields, I will lose less soil than if I do plow the fields. Plowing disrupts the soil and breaks up roots that help hold soil in place.” The farmer also notices some other differences in the two plots. The plants in the no-till plots are taller. The soil moisture seems higher. She decides to repeat the experiment. This time she will measure soil moisture, plant growth, and the total amount of water the plants consume. From now on she will use no-till methods of farming.

Scientific Theories

When scientists have collected data and drawn conclusions, they may write a paper. Their paper may be published in a scientific journal. A scientific journal is a magazine for the scientists who are interested in a particular field. Before the paper is published, other scientists examine it to try to find mistakes. They analyze the procedures and findings to ensure that the conclusions are in line with the data. This is called peer review. If the paper is found to be accurate it is printed in the journal.

Other papers are published on the same topic in the journal. The evidence for or against a hypothesis is discussed by many scientists. Sometimes a hypothesis is repeatedly shown to be true and never shown to be false. The hypothesis then becomes a scientific theory.

In science, a theory has been repeatedly shown to be true. A scientific theory is an explanation supported by many observations. However, a theory may be disproved if conflicting data is discovered. Many important theories have been shown to be true by many observations and experiments and are extremely unlikely to be disproved. These include the theory of plate tectonics and the theory of evolution.

Scientific Laws

Scientific laws are principles that describe the behavior of natural phenomenon. While the cause of the law is not always known it always applies under the same conditions.  For example, we know that gravity always applies when we drop something.  Another examples of  a law you may be familiar with include any of Newton’s Laws of Motion.

Scientific Models

Scientists use scientific models to help them understand and explain ideas. Scientific models explain objects or systems in a more simple way. Models often only show only a part of a system. Models help scientists to make predictions about complex systems.

Some models are something that you can see or touch such as a globe or a physical model of the Earth’s structure. Some models are used to help scientists explain a concept. An example is how Earth got its moon. A Mars-sized meteor hit Earth and rocky material broke off of both bodies. This material orbited Earth and then came together to form the Moon. Scientists create some models with computers. Computers can handle enormous amounts of data. For example, Earth’s climate depends on an enormous number of factors. Climate models can predict how climate may change as the Earth changes.

A collision showing a meteor striking Earth.

Lesson Summary

• Scientists ask questions about the natural world.
• Scientific method is a set of logical steps that can be used to answer these questions.
• A hypothesis is a possible explanation to a problem that can be tested.
• A scientific theory is a hypothesis that has been shown to be true many times over.
• A scientific law explains the behavior of natural phenomenon.
• Scientific models represent real things but are simpler.

Lesson Review Questions

1. Describe a benefit of using a scientific model.

2. A scientist was studying the effects of oil contamination on ocean seaweed. He believed that oil runoff from storm drains would keep seaweed from growing normally. He had two large aquarium tanks of equal size. He kept the amount of dissolved oxygen and the water temperature the same in each tank. He added some motor oil to one tank but not to the other. He then measured the growth of seaweed plants in each tank. In the tank with no oil, the average growth was 2.57 cm/day. The average growth of the seaweed in the tank with oil was 2.37 cm/day. Based on this experiment, answer the following questions:

• What was the question that the scientist started with?
• What was his hypothesis?
• Identify the independent variable, the dependent variable, and the constants.
• Identify the experimental group and the control group.
• Analyze the data.  Make a conclusion statement based on your analysis.

3.  Differentiate between a scientific theory and a scientific law.  Provide an example of each in your response.