Why would a scientist do an experiment?
What is the difference between an
observation and an inference?
What is a variable?
Warm up answers
To answer a question
Direct observation v. interpretation
A variable is what can change in an
Aspects of an experiment that may change
Part of an experiment that the scientist
manipulates to study the effects of the
Part of an experiment that the scientist is
Any change to this variable is caused by the
Unless there is a problem with the controlled
Controlled variable (s)
Part of an experiment that must stay the
same for all trials
Parts to an experiment
Read chapter 1 section 2
Vocab on page 30
Questions and answers on page 15
Figure 1-8 Redi’s Experiment on
OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat.
HYPOTHESIS: Flies produce maggots.
Uncovered jars Covered jars
jars, type of meat,
gauze covering that
keeps flies away from
appear Maggots appear No maggots appear
CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous
generation of maggots did not occur.
Figure 1-10 Spallanzani’s Experiment
Gravy is boiled. Flask is Gravy is teeming
open. with microorganisms.
Gravy is boiled. Flask is Gravy is free of
Figure 1-11 Pasteur’s Experiment
Broth is boiled. Broth is free of Curved neck Broth is
microorganisms is removed. teeming with
for a year. microorganisms.
What is the difference between a hypothesis,
a conclusion, and a theory?