Collecting Evidence Like a Scientist

You will learn how to collect observations and measurements as evidence during an investigation.

Evidence is the information you gather that helps you answer a question or show that something is true. Scientists do not just guess. They look, listen, measure, and write things down. Then they use what they collected to explain what happened.

There are two main ways to collect evidence. One way is an observation, which is something you notice using your senses, like a leaf turning brown or water feeling cold. The other way is a measurement, which is a number you get using a tool, like 25 centimeters or 30 degrees Celsius. Both kinds of evidence are useful, but numbers help you compare things more exactly.

Imagine your class plants bluebonnet seeds in cups outside the classroom. You want to know if the plants grow better in sunlight or in shade. Each morning you look at the plants and write what you see, such as "the leaves are bright green" or "the soil looks dry." That is an observation. Then you use a ruler to measure each plant and write "4 centimeters" in your notebook. That is a measurement. After two weeks, your notebook is full of evidence, and you can look back and see which plants grew taller.

Good scientists write down evidence right away, not later from memory. They record the date and time. They use the same tool each time so the numbers can be compared fairly. They write down exactly what they see, even if it is surprising or not what they expected. Changing your data to match what you hoped for is not honest science.

Try it: If you wanted to show that ice melts faster on a sunny sidewalk than in the shade, what measurement could you collect and what tool would you use?