PHYSICAL SCIENCE A NOTES

SCIENTIFIC LAW vs. SCIENTIFIC THEORY

A scientific law is a law of nature that tells WHAT happens every time during an experiment.

  • Examples include the law of gravity, law of conservation of mass, Ohm's Law, and Newton's Laws of Motion

A scientific theory is a possible explanation of HOW or WHY something happens.

  • Examples include the kinetic theory of matter, Dalton's Atomic Theory, the Plate Tectonics theory ("Continental Drift"), the Theory of Evolution, the Big Bang Theory, and Einstein's Theory of Relativity
VARIABLES AND CONSTANTS

When scientists solve problems, they look for patterns (relationships, cause and effect).

In order to solve a problem, a scientist must consider all of the variables involved in an experiment.

A variable is any factor in an experiment that affects the outcome (results).

  • It is anything that could change the answer you get or affect the experiment in some way.
  • For example: A balloon is a piece of equipment that will be used during the first lab in this class.  What are all the variables involved with a balloon?
    • color
    • size
    • shape
    • used or new?
    • what's inside it?
    • thickness
    • material it's made of
    • hole in it?
    • amount inside it
In an experiment, there are many, many variables!  A scientist can only look for a relationship between two at a time, though.

These two variables are the important variables in an experiment.

1. independent variable

  • listed in the problem
  • you control it
  • you set the values of it before you start the experiment
  • changes value every trial
2. dependent variable
  • listed in the problem
  • you cannot control it
  • it changes according to the independent variable
  • it "depends" on the value of the independent variable
  • you measure its value/changes during the experiment
All other variables in the experiment must be kept constant so they cannot affect the experiment's answer.
  • Constant means staying the same, unchanging, just one value