Scientific Investigations

1. Scientific Investigations

2. When you hear the word science, lots of things probably come to your mind. Maybe stuff like this:

3. We’re interested in knowing what you think. So, tell us: What is Science? 1

4. Maybe you wrote, “Science is learning about plants and animals and rocks and planets” Or, maybe you wrote, “Science has a lot of facts and hard vocabulary words” You might even have written, “Science is all about boring stuff I don’t care about. I like art and social studies and music a lot better.”

5. None of these answers is wrong. Science involves all of these things. (Like anything else, science can be boring. Most scientists love their jobs, but even they get bored sometimes.) Still, we need a definition of science that we can all share. That way, we know we’re all talking about the same thing.

6. The following question might help us make a definition of science. What can be done during science class that won’t be done during math, language arts, or social studies? (Give examples) 2

7. Maybe you wrote that you go outside and watches butterflies getting nectar from flowers. Maybe you wrote that your class puts baking soda into vinegar and describes what happens.

8. You might even have written that you use tools such as magnifying glasses to study fossils.

9. Answers like these help us figure out how science is different than other subjects. VOCABULARY Science makes knowledge that humans use to understand things and events in the natural world.

10. Ways of Making Scientific Knowledge How do people make scientific knowledge? What does it take? One way to make scientific knowledge is to observe things and events many times.

11. Consider the example of the Sun People have seen the Sun rising and setting for thousands of years. These repeated observations help us trust our knowledge about what the Sun will do each day.

12. More recently, scientists have used special telescopes to figure out that the Sun is a star made mostly of hydrogen and helium. So, repeated observation of the natural world is one way to make scientific knowledge.

13. Think ahead to the year 2023. Predict two things that will happen to broad leaf trees (maples and oaks, for example) as the seasons change from summer to fall, And then from fall to winter. 3

14. Do you think your prediction will come true? 4 Explain your answer 5

15. VOCABULARY Fair test is another way to make reliable knowledge by planning and running an experiment. Why is it called a “fair” test?

16. Look at it this way. Imagine that you’re playing a game, but the rules of the game make it completely impossible for you to win. In other words, The results of the game are known before the game even starts! The game is unfair.

17. How is a fair game different than an unfair game? 6 A fair test is like a fair game. A fair test has carefully defined rules which do not change during the test. Changing the rules during the test would be cheating!

18. Results of a fair test are not known ahead of time. Scientists who plan and run a fair test may think they know what the results will be But It is possible for the actual results to be different from what the scientists expect.

19. A fair test leaves room for unexpected results. There’s a lot that goes into planning and running a fair test. A story has been written to take you through the process of doing both planning and running a fair test.

20. Planning and Running a Fair Test

21. John and Brenda are 6th grade students learning about plants. One day, they become curious about something they’ve noticed: Plant stems always grow up into the air, And Plant roots always grow down into the soil. But why?

22. So, John and Brenda ask their teacher this question: What makes the stems of plants grow up and the roots of plants grow down? 7

23. At this point, the teacher has 2 choices. She can give them the answer. She can help them discover the answer.

24. When do you remember things better? When a teacher gives you an answer, or when you discover the answer by yourself? 8

25. The teacher asks, “Well, what do you think? What makes stems grow up and roots grow down?”

26. After thinking for a moment, Brenda says, “Light. A little light gets through the soil. So, light is what causes stems to grow up and roots to grow down.”

27. Okay, now stop. Let’s think about this story as a scientist would.

28. Fair tests usually start with curiosity (something that grabs your interest and that you want to know more about) You can then put your curiosity in the form of a question. A good question helps you figure out exactly what you want to know more about.

29. Finally, You can make a statement that is a possible answer to your question. Notice that we said “a possible answer”, Not “the right answer”

30. If you already knew the right answer, You probably wouldn’t be curious about what you saw, right? VOCABULARY Your statement just needs to be one that you can support, disprove, or change because of observation or a fair test. Scientists call such a testable statement a hypothesis

31. What are John and Brenda curious about? 9 What question helps them figure out what they want to know more about? 10

32. What is their hypothesis, or testable statement? 11

33. John, Brenda, and their teacher plan and set up a fair test to figure out whether light makes stems grow up and roots grow down. They take the following steps. 1. They soak four corn seeds in water overnight. This will help the seeds sprout quickly. 2. They put wet sponges into two glass Petri dishes.

34. 3. They put two corn seeds in each dish, and tape the dishes shut. 4. They balance the dishes on their sides and tape them to the table so they will not fall.

35. They cover the left dish with a box so no light reaches the seeds. They shine a light over the other dish.

36. Everything else about the dishes is exactly the same: Type of corn in the dishes Amount of water in the sponges, And so on.

37. In 5 days, they’ll lift the box and compare the seeds in the 2 dishes What do you think will happen to the seeds in the light? 12

38. John says the stems will grow up to reach the light and the roots will grow down to get away from the light Okay, how about the seeds in darkness? 13

39. John and Brenda talk to each other then decide: The stems and roots in darkness won’t know which way to grow, so they’ll grow all over the place. They’ll be totally confused! The teacher only said, we’ll see if you are right in 4 days

40. Let’s stop and think like scientists. To plan a fair test, you must identify 3 things: VOCABULARY Independent variable This is something that you control or change during your experiment

41. Dependent variable What you measure, count, or observe happening due to the change to the independent variable Constants All of the other things that should be kept the same throughout the fair test (everything except your independent variables)

42. The goal of a fair test is to figure out what effect (if any) the independent variable has on the dependent variable By keeping all other conditions constant, your fair test will examine only the relation between the independent variable and the dependent variable.

43. What is the independent variable in John and Brenda’s fair test? 14 What is the dependent variable in John and Brenda’s fair test? 15

44. What are some constants in the fair test? (name at least 3) 16

45. As you plan a fair test, you should also make a prediction about how the dependent variable will react to the independent variable. In other words, you should predict the results of your fair test.

46. Your prediction must be based on your hypothesis. By comparing your prediction with the actual results of the fair test, You can judge whether your hypothesis was supported, not supported, or somewhere in-between. Remember a hypothesisis your statementthat you can support, disprove, or change because of observation or a fair test.

47. What prediction did John and Brenda make? 17 stems will grow up to reach the light and the roots will grow down to get away from the light stems and roots in darkness won’t know which way to grow, so they’ll grow all over the place

48. Scientists often put a hypothesis into an “if-then” statement. If I change the independent variable then this will happen to the dependent variable

49. Look at John and Brenda’s hypothesis that they made then write it in an “if-then” sentence. 18

50. Thinking About the Results of a Fair Test