Designing Experiments

September 2, 2015(1.3 in your books)

Meme Moment

Scientist of the Day

Lise Meitner• Helped discover nuclear

fission• Should have won Nobel Prize• Direct competitor of Irene

Joliot-Curie (another Scientist of the Day)

• Has an element named after her

• Competitor tried to have her killed

• Escaped Nazis using Otto Hahn’s jewels

Homework1. A. Was the soda & Mentos experiment a

controlled experiment?B. Why or why not?

2. A. How could you find data for a controlled experiment from the observations we collected?

B. What methods or tools could you use?3. If you got to do it again, what would you change

about the experiment?

6B

Pick-Your-OwnScientist of the Day

4-part project:

1. Run the “observation or inference” activity for the day

2. Briefly present your scientist’s story to the class3. Small poster for the hallway4. 2-page paper on scientist’s life and research –

citations needed

Due Date 1: Friday, September 11 sign-up for scientist & slot. Bring 2 back-up names!

8th grade

VocabularyScientific inquiry: How scientists study the natural world and make explanations for their observations

Hypothesis: A scientific prediction that is a possible answer to a question.

Data: The observations you collect. Can be facts, pictures, numbers, etc

Controlled Experiments, part 2

• A controlled experiment is one where only 1 variable is changed at a time

• This makes it easy to see cause & effect• When you change 1 variable, you’re hoping to

see a change in the result

Independent variable: The variable you change on purpose

Dependent variable: The change you see as a result of changing the independent variable

Scientific Theories• A scientific theory is very different from a normal

theory. There are 3 ways to use a theory:

1. Normal person: just a guess. Sometimes silly.“Sam is late for class. He must have been abducted by aliens!”2. Semi-scientific: sometimes people will use hypothesis and theory interchangeably.“My theory is that Diet Coke & Mentos is the biggest explosion.”3. Scientific theory: An almost-indisputable explanation that’s constantly being tested“Germ theory states that some diseases are caused by microorganisms like bacteria.”

Scientific Laws vs. Theories

Scientific law: Describes patterns in nature without trying to explain why. Usually involves math.

Scientific theory: Explains why you see something in nature. The observations are indisputable facts and the theory is constantly being tested

The main difference is the “why.” e.g. It’s germ theory because you can’t just throw math at it and figure out what disease bacteria will cause. (This is a very simplified explanation.)

Questions• Any questions about the slides?

• Any new questions?

New Questions• What was the most dangerous dinosaur?Possibly the spinosaurus, which hunted on land and sea.

New Questions• What is the biggest snake in the world?Green anaconda is the heaviest (227 kg); reticulated python is the longest (10 m).