1.2 scientific inquiry 1 “how does soap clean?” “where does plastic come from?” “why do we...
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1.2 Scientific Inquiry1
“How does soap clean?”
“Where does plastic come
from?”
“Why do we need sunscreens?”
Have you ever wondered…
1.2 Scientific Inquiry2
“Why do we get hot when we
work out?”
“Why does fire transform wood to ashes, but ashes can’t become wood again?”
Have you ever wondered…
1.2 Scientific Inquiry9
“I think sugar dissolves faster
in hot water.”
Does sugar dissolve faster in hot water?
1.2 Scientific Inquiry10
hypothesis: a tentative explanation for something, or a tentative answer to a question.
“I think sugar dissolves faster
in hot water.”a hypothesis!
Does sugar dissolve faster in hot water?
1.2 Scientific Inquiry11
experiment: a situation specially set up to observe how something happens or to test a hypothesis.
Testing a hypothesis requires scientific evidence from experiments.
1.2 Scientific Inquiry12
One experimental setup:
Objective observation:The time it takes the sugar to dissolve changes in each trial.
1.2 Scientific Inquiry13
One experimental setup:
Does this support our hypothesis? YES NO MAYBE
“I think sugar dissolves faster in hot water.”
1.2 Scientific Inquiry14
One experimental setup:
Does this support our hypothesis? YES NO MAYBE
“I think sugar dissolves faster in hot water.”
1.2 Scientific Inquiry15
One experimental setup:
What could affect dissolving?
• Water temperature• Amount of sugar• Amount of water
Variables
1.2 Scientific Inquiry16
variable: a quantity that is measured or changed in an experiment or observation.
What could affect dissolving?
• Water temperature• Amount of sugar• Amount of water
Variables
We don’t know if our hypothesis is correct because more than one variable changed at the same time!
1.2 Scientific Inquiry17
A second experimental setup:
Objective observation:The time it takes the sugar to dissolve changes in each trial.
1.2 Scientific Inquiry18
What could affect dissolving?
• Water temperature• Amount of sugar• Amount of water
Control variables (do not change)
A second experimental setup:
1.2 Scientific Inquiry19
What could affect dissolving?
• Water temperature• Amount of sugar• Amount of water
Experimental variable (changes)
A second experimental setup:
1.2 Scientific Inquiry20
Does this support our hypothesis? YES NO MAYBE
“I think sugar dissolves faster in hot water.”
A second experimental setup:
1.2 Scientific Inquiry21
Does this support our hypothesis? YES NO MAYBE
“I think sugar dissolves faster in hot water.”
A second experimental setup:
1.2 Scientific Inquiry22
variable: a quantity that is measured or changed in an experiment or observation.
experimental variable: the single variable that is changed to test its effect.
control variable: variables that are kept constant.
1.2 Scientific Inquiry23
These numbers are different!
The same experiment is repeated 3 times.
The measurements are different each time.
Is the investigator making a mistake?
1.2 Scientific Inquiry24
error: the unavoidable difference between a real measurement and the unknown true value of the quantity being measured.
• Measurements always contain some uncertainty or error.
• In this case, error is not a mistake.
Error and uncertainty
1.2 Scientific Inquiry26
Why take the average?
• To improve accuracy
• Comparing the actual measurement
with the average gives you an
estimate of the error
Accuracy
1.2 Scientific Inquiry27
How can we know the error if we don’t know the true value?Assume the average is the true value.
Accuracy
1.2 Scientific Inquiry29
Estimated error: +/– 4 seconds
Estimated error: +/– 4 seconds
Does sugar dissolve slower in warmer water?
1.2 Scientific Inquiry30
0.6 seconds
Estimated error: +/– 4 seconds
Estimated error: +/– 4 seconds
Does sugar dissolve slower in warmer water?
1.2 Scientific Inquiry31
0.6 seconds
Estimated error: +/– 4 seconds
Estimated error: +/– 4 seconds
No, the difference in time (0.6 s) is not significant, because it is smaller than the
estimated error (4 s).
Does sugar dissolve slower in warmer water?