Unit 8 — Scientific Investigation

Welcome back!

Scientists are curious people.

They ask questions, make careful observations, test ideas, and learn from evidence.

In Grade 2, you learned the basic steps of a scientific investigation.

Now you will build on those skills by planning better investigations, making careful measurements, and drawing conclusions from evidence.

Asking Good Questions

Every investigation begins with a question.

A good scientific question can be tested.

Examples include:

• Which paper towel absorbs the most water?
• Does sunlight affect plant growth?
• Which type of soil holds the most water?
• Which toy car rolls the farthest?

Questions that can be investigated help scientists learn about the world.

Making a Hypothesis

A hypothesis is a prediction based on what you already know.

For example:

"I think plants that receive more sunlight will grow taller."

A hypothesis is not a random guess.

It is an idea that can be tested.

Conducting a Fair Test

A fair test changes only one thing at a time.

Suppose you want to know whether sunlight affects plant growth.

Both plants should have:

• the same type of seed
• the same amount of water
• the same soil
• the same size pot

The only difference should be the amount of sunlight.

This helps you know what caused the results.

Observing Carefully

Scientists observe using:

• sight
• hearing
• touch
• smell
• measuring tools

Careful observations provide reliable information.

Recording observations every day often reveals patterns that might otherwise be missed.

Measuring and Recording Data

Scientists often measure:

• length
• height
• weight
• temperature
• time
• distance

Measurements are usually recorded in tables or notebooks.

Accurate records help scientists compare results.

Drawing Conclusions

After collecting evidence, scientists ask:

• Did my results support my hypothesis?
• What did I learn?
• Were there any surprises?
• What questions do I have now?

Sometimes the results are different from what was expected.

That is still an important scientific discovery.

Sharing Discoveries

Scientists share their work so others can learn from it.

They may use:

• reports
• charts
• drawings
• photographs
• presentations

Sharing evidence helps science continue to grow.

Activity

Design a simple investigation.

Write:

• your question
• your hypothesis
• the materials you will use
• the steps you will follow
• what you will measure
• your conclusion after completing the investigation

Practice

Answer these questions.

What is a hypothesis?

Why should a fair test change only one thing?

Why are careful measurements important?

What should scientists record during an investigation?

Why do scientists share their discoveries?

Review

Today you learned:

• scientific investigations begin with testable questions
• hypotheses are ideas that can be tested
• fair tests change only one variable
• careful observations and measurements provide evidence
• conclusions should be based on the evidence collected

Science helps us understand the world by asking questions, testing ideas, and learning from reliable evidence.

Looking Ahead

Next we will study ecosystems and discover how plants, animals, and their environments depend upon one another for survival.