Types of scientific InquiryScientific inquiry is a set of methods that scientists use to gather information and explain the natural world. All scientific inquiry uses similar processes to find answers to questions or to find relationships between variables. A variable is any condition that could change in an inquiry. A variable that is deliberately changed by the investigator is called the independent variable. A variable that changes in response to the independent variable, but is not directly controlled by the investigator, is called the dependent variable.

Two common types of scientific inquiry are the controlled experiment and the observational study.

variable: ▶ any condition that changes or varies the outcome of a scientific inquiry

independent variable: ▶ a variable that is changed by the investigator

dependent variable: ▶ a variable that changes in response to the change in the independent variable

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Reading TipScan for Specialized Vocabulary

Before reading, scan the text to find the highlighted vocabulary. Check the margins for definitions of these words. Knowing the meaning of these words ahead of time can help you understand the ideas and information they refer to in the text.

Figure 1 Observations of the night sky have helped us to better understand the Universe.

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Scientists assume that the natural world can be explained and understood. Hundreds of years ago, people believed that all of the objects in the sky revolved around Earth. Careful scientific observations and technological advances, such as the invention and use of the telescope, have provided evidence that the Sun is the centre of our Solar System. Scientists now know that the Universe is very different from how they had first thought of it (Figure 1).

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Controlled ExperimentYou can perform a controlled experiment to determine whether one variable causes an effect on another variable. This means that you can control (change) the independent variable to find out if it causes a change in the dependent variable. For example, suppose you want to determine how the amount of salt in a given volume of water affects the boiling point of the water. A controlled experiment would be the best approach. In this case, the investigator would use different amounts of salt (independent variable) and observe the effect, if any, on the boiling point of the water (dependent variable).

observational study Often the purpose of a scientific inquiry is to answer a question by gathering scientific information. An observational study involves observing a subject or event without interfering with or influencing it. Observational studies start with observations that lead to a question. Sometimes the researchers start with a specific prediction about the answer to the question. Sometimes they also have an explanation for their prediction—but not always. An explanation might be possible only after evidence is collected.

Sciences such as astronomy, geology, and ecology rely heavily on observational studies (Figure 2). Observational studies are done when an investigator cannot control the variables because of safety, time, distance, cost, or ethical considerations.

controlled experiment: ▶ an experiment in which the independent variable is purposely changed to find out what change, if any, occurs in the dependent variable

observational study: ▶ the careful watching and recording of a subject or event to gather scientific information to answer a question

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Text features include headings, sidebars, graphics, and margin definitions. Scan a text before reading to identify the features it uses. This process can help you organize how you read a text and alert you to important information.

Neptune

Uranus

Saturn

Jupiter

Mars

Earth

Venus

Mercury

Figure 2 To find out how long it takes for each of the planets to orbit the Sun, scientists had to carefully observe the planets from Earth over long periods of time.

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Figure 3 When scientists first observed the northern lights (aurora borealis), they probably wondered what caused them.

scientific Investigation skillsCertain skills are important for conducting any investigation. These skills can be organized into four categories:

1. initiating and planning

2. performing and recording

3. analyzing and evaluating

4. communicating

Initiating and PlanningAll scientific investigations begin with a question. The question may arise from observations of a natural event, from an individual’s curiosity (Figure 3), or from previous experiments or studies.

Some questions cannot be answered through scientific investigation, so it is important to ask the right questions. A scientific question must be testable. Testable questions have certain characteristics:

• They must be about living things, non-living things, or events in the natural world.

• They must be answerable through scientific inquiries such as controlled experiments or observational studies.

• They may be answered by collecting and analyzing data.

TRY This QuEstions LEading to sciEntific inQuiry

SkillS: Planning, Communicating

The type of question asked in a scientific inquiry determines, to a large degree, the most appropriate method to answer the question. In this activity, you will identify the best type of scientific inquiry—controlled experiment or observational study—for answering a series of questions.

Equipment and Materials: notebook or paper; pen or pencil

1. Read the following questions:

What factors determine the strength of an • electromagnet?

What are the most common types of waste • materials dumped at the landfill?

Will an iron object rust most quickly in air, water, • or oil?

How soon after sunset does the sky become • dark enough for us to see stars?

What kinds of plants and animals are common • in the forests in my area?

a. Carefully study each statement and indicate what type of scientific inquiry would be most appropriate.

B. For each question, briefly describe how you would carry out the inquiry.

3.B.4., 3.B.9.

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If a controlled experiment should be performed to answer the testable question, you may propose a possible answer. The possible answer is based on existing scientific knowledge. This is called a hypothesis. The hypothesis is directly related to the question.

A hypothesis suggests a relationship between an independent variable and a dependent variable. A hypothesis serves two functions: (1) it proposes a possible answer to the question, along with an explanation, and (2) it suggests a method of obtaining evidence that will either support or reject the proposed explanation.

If you do not have a scientific explanation and cannot make a hypothesis, then you can make a prediction. A prediction is a statement that predicts the outcome of a controlled experiment, without an explanation. A prediction is not a guess: it is based on prior knowledge and logical reasoning.

A hypothesis usually includes a prediction. It is often written in the form “If …, then …, because ….” The “if … then” part is the prediction; the “because …” part is the explanation.

A hypothesis or a prediction identifies the independent variable and the dependent variable. It also suggests an experimental design for conducting a fair test. The experimental design briefly describes the procedure.

Planning the investigation involves the following:

• identifying the independent and dependent variables

• determining how the changes in the variables will be measured

• specifying how to control the variables not being tested

• selecting the appropriate equipment and materials (Figure 4)

• identifying and addressing safety concerns

• deciding on a format for recording observations

hypothesis: ▶ a possible answer or untested explanation that relates to the initial question in an experiment

prediction: ▶ a statement that predicts the outcome of a controlled experiment

experimental design: ▶ a brief description of the procedure by which a hypothesis or prediction is tested

Figure 4 The equipment used in space exploration is very specialized.

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Performing and RecordingAfter planning an investigation, it is important to follow the procedures carefully (Figure 5). That does not mean that the procedures cannot change. If the procedures present problems, they should be changed, and any changes should be recorded. If the problems cannot be overcome, you may have to go back to the planning stage and start again.

It is important to be aware of possible safety concerns with the procedure. Carefully read the safety guidelines in the Skills Handbook before beginning an investigation, and refer to them frequently.

While performing an investigation, you will need to make accurate observations and record them carefully. Observations are any information that is obtained through the senses. Observations can be quantitative (numerical) or qualitative (non-numerical).

A quantitative observation is based on measurements or counting (Figure 6). Examples of quantitative measurements include length, mass, temperature, and population counts. Measuring is an important skill in making observations. Not only must the right measuring tool be selected, but it must also be used in such a way as to provide a precise and accurate measurement.

quantitative observation: ▶ a numerical observation based on measurements or counting

Figure 6 Two scientists make quantitative observations on a polar bear.

Figure 5 A scientist follows the procedure he has outlined.

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A qualitative observation is a description of the qualities of objects and events, without any reference to a measurement or a number. Common qualitative observations include the state of matter (solid, liquid, or gas), texture, and odour. These qualities cannot be measured directly or easily.

The method of recording your observations depends on the type of observation. Quantitative observations are often recorded in a data table. Qualitative observations can be written in words or recorded in pictures or sketches (Figure 7). Remember to record your observations clearly and accurately so that you do not have to rely on memory when you report your findings.

analyzing and EvaluatingTables, lists, and drawings of observations are not the final products for the data collected during an investigation. Analyzing, or carefully studying, the observations can provide more information than the raw data itself. You can also plot graphs from the quantitative data to show patterns and trends more clearly. Analyzing observations also helps to identify any errors in measurement.

A very important skill in a scientific investigation is evaluating the evidence that is obtained through observations. The quality of the evidence depends on the quality of the plan, the procedures, the equipment and materials, and the skills of the investigator. In order to evaluate the evidence, you need to evaluate all aspects of the investigation.

qualitative observation: ▶ a non-numerical observation that describes the qualities of objects or events

Figure 7 These science students record qualitative observations as drawings.

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Learning TipWord Origins

The word “quantitative” comes from the word “quantity,” which refers to an amount or number. The word “qualitative” comes from the word “quality,” which refers to the characteristics of something.

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The purpose of analyzing and evaluating observations is to answer the question posed at the beginning of an investigation. You may have evidence that you can use to confidently answer the question. Or you may conclude that you do not have enough evidence to answer the question. If your evidence confirms the prediction, then the hypothesis is supported. Note that this does not prove the hypothesis to be true. If your evidence does not confirm the prediction, then the hypothesis may not be an acceptable explanation. A scientific investigation is not a failure simply because the hypothesis was rejected. The investigator just has to look at another possible explanation to test.

Scientific research usually requires more than a single experiment. Sometimes other investigators repeat the investigation to see if their results are the same. A scientific investigation often leads to new questions, which then lead to other investigations and other questions.

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Reading TipSearch for the Main Idea

During reading, search for the main idea of the text. Check the first, second, and last sentences of a paragraph. Sometimes, you may have to infer a main idea that is not stated directly.

TRY This anaLyzing data

SkillS: Analyzing, Communicating

Data collection involves the recording of information in an organized way. Analyzing involves studying the data to uncover patterns and trends. In this activity, you will analyze data from a sample investigation. The data in Table 1 show the distance that Chad can ride his bicycle in a given amount of time.

Equipment and Materials: ruler; graph paper; notebook; pen or pencil

1. The data in Table 1 show the distance covered by Chad as he rides his bicycle along a measured track.

2. Use the data in the table to plot a line graph.

3. Starting at the (0, 0) point on your graph, use a ruler to draw a straight line through your data so that it is touching (or near to) as many points as possible. The data points should be evenly scattered around either side of the line you draw.

a. Make a general statement about the relationship between the time and the distance travelled.

B. Is this relationship easier to see from the data or from the graph? Explain.

C. Use the graph to estimate how far Chad had travelled after 45 s and after 2 min (120 s).

D. Propose an explanation for why all of the points do not fall exactly on the straight line.

E. Look at the angle of the line you drew in Step 3. What do you think this line represents?

Table 1 Distance Travelled by Bicycle

Time (seconds)

Distance (metres)

0 0

10 50

20 120

30 190

40 270

50 350

60 430

70 510

80 580

90 670

100 750

3.B., 6.A., 6.C.

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CommunicatingOne of the important characteristics of scientific investigation is that scientists share their information (Figure 8). Before scientific data can be published in a scientific journal, it must be examined by other scientists in a process called peer review. Other experts check that the data are valid and the science is correct.

Clear and accurate communication is essential for sharing information. It is important to share not only the evidence, but also the process by which the evidence was obtained. If the investigation is to be repeated by others, it is just as important to share the design and procedures.

By sharing their data and the techniques they used to obtain, analyze, and evaluate their data, scientists give others the opportunity to both review the data and use it in future research. The most common method for communicating with others about an investigation is by writing a report or giving a presentation after the investigation is complete.

Figure 8 Scientists sharing their information with each other is a key characteristic of scientific investigation.

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1.1 Wrap up • Curiosity about what we see around us often leads to questions that trigger

scientific investigations.

• One type of scientific inquiry is the controlled experiment, in which the researcher keeps all but two variables constant, changes one (the independent variable), and observes the other (the dependent variable).

• A second type of inquiry is the observational study, in which the researcher collects data by observing a situation without affecting it.

• Scientific investigation skills include

— initiating and planning (asking a question and deciding on the best way to find an answer)

— performing and recording (carrying out the procedure and making observations)

— analyzing and evaluating (searching for patterns in the observations)

— communicating (sharing findings with others)

TRY This Pass it on!

SkillS: Evaluating, Communicating

Accurate communication is as important in science as it is in everyday life. In this activity, you will work as a class to demonstrate the importance of accurate communication and the need to develop and refine your skills in this area.

Equipment and Materials: paper; pen or pencil

1. Your teacher will create a simple statement, write it on a piece of paper, and then whisper it to a student in class.

2. That student will write the message on a piece of paper and then whisper the message to another student.

3. The message will be passed on until every person in the class has received the message. Your teacher will record the sequence of students that the message followed.

4. The rules are simple:

You must write exactly what you hear.•

You must state the message only once.•

You must whisper the message.•

You cannot show other students what you • have written.

5. The last person to receive the message will repeat it out loud to the class.

6. The teacher will then write the original message on the board. All students will then write their version of the message under the previous message.

a. How closely did the final message resemble the original message? Explain.

B. How does this activity demonstrate the need for clear, accurate communication?

C. Give an example from real life of how the message “received” differs from the message “sent.”

D. Based on this activity, suggest a set of guidelines to ensure clear, accurate communication.

3.B.8., 3.B.9.

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