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We use our senses to gather evidence for scientific investigations, they're our most powerful tools.

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A scientist observed this orange-colored scum on a pond in her neighborhood. She wondered what the scum is and why it was there. She decided to do an investigation to find answers to her questions. Scientific investigations often result when observations like this raise questions.

What Are Observations?

An observation is any information that is gathered with the senses. Our senses include vision, hearing, touch, smell, and taste. We see with our eyes, hear with our ears, touch with our hands, smell with our nose, and taste with our tongue. We can also extend our senses and our ability to make observations by using instruments such as microscopes, telescopes, and thermometers.

Q: How do these instruments extend human senses and our ability to make observations?

A: Microscopes and telescopes extend the sense of vision. They allow us to observe objects that are too small (microscopes) or too distant (telescopes) for the unaided eye to see. Thermometers extend the sense of touch. Using our sense of touch, we can only feel how warm or cold something is relative to our own temperature or the temperature of something else. Thermometers allow us to measure precisely how warm or cold something is.

Using Observations to Gather Evidence

Besides raising questions for investigation, observations play another role in scientific investigations. They help scientists gather evidence. For example, to investigate whether a chemical change has occurred, a scientist might observe whether certain telltale signs are present. In some chemical changes, for example, a substance turns from one color to another. You can see an example of this in the Figure below. In other chemical changes, an odor is produced or gas bubbles are released. All of these changes can be observed with the senses.

Shiny copper new pennies and dull brown old pennies

Some of these pennies are shiny and copper colored. That’s how pennies look when they are new. The older pennies are dull and brown. Copper at the surface of these pennies has combined with air to become a different substance with different properties. The change in color shows that a chemical change has occurred.

Q: Some chemical changes release heat. How could this change be observed?

A: The sense of touch—or a thermometer—could be used to observe an increase in temperature.


  • An observation is any information that is gathered with the senses.
  • Observations raise questions that lead to scientific investigations. Observations also help scientists gather evidence in investigations.


  1. What is an observation?
  2. What senses can we use to make observations?
  3. Why are observations important to scientific investigations?


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observation Any information that is gathered with the senses.

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