Download Scientific Theory or Law?

Scientific Theory or Law?
Each slide describes a theory
or law of science. Use the
definitions of theory and law
to decide which are which.
Rules and Background
 Sit in groups of 2 and quietly discuss whether each slide describes
and theory or law of science before writing your answer on your
whiteboard.
 A scientific theory is a well-tested explanation for a wide range of
observations or experimental results.
 A large body of evidence supports this.
 Future evidence can change or even nullify a theory.
 A scientific law is a statement that describes what scientists
expect to happen under a certain set of conditions.
Theories do NOT turn into laws!!!
Cell Theory
 All living organisms are composed of
one or more cells.
 The cell is the basic unit of structure,
function, and organization in all
organisms.
 All cells come from pre-existing, living
cells.
Laws of Planetary Motion
 The orbit of every planet is an ellipse with the
Sun at one of the two foci.
 A line joining a planet and the Sun sweeps out
equal areas during equal intervals of time.
 The square of the orbital period of a planet is
proportional to the cube of the semi-major axis
of its orbit.
Ideal Gas Law
 PV = nRT
 where P is the pressure of the gas, V is the volume
of the gas, n is the amount of substance of gas (also
known as number of moles), T is the temperature
of the gas and R is the ideal, or universal, gas
constant, equal to the product of the Boltzmann
constant and the Avogadro constant.
Atomic Theory
Matter is composed of discrete units
called atoms, as opposed to the
earlier concept which held that
matter could be divided into any
arbitrarily small quantity.
Germ Theory
 Some diseases are caused by
microorganisms. These small organisms,
too small to see without magnification,
invade humans, animals, and other
living hosts. Their growth and
reproduction within their hosts can
cause a disease
Laws of Thermodynamics
 If two systems are both in thermal
equilibrium with a third system then they
are in thermal equilibrium with each other
 This states that energy can be neither
created nor destroyed. However, energy can
change forms, and energy can flow from
one place to another. The total energy of an
isolated system remains the same.
Theory of Evolution
 All life on Earth is descended from a last
universal ancestor that lived approximately
3.8 billion years ago. Repeated speciation
and the divergence of life can be inferred
from shared sets of biochemical and
morphological traits, or by shared DNA
sequences.
Big Bang Theory
Cosmological model that
describes the early
development of the
Universe.
Newton’s Laws of Motion
 An object either is at rest or moves at a constant
velocity, unless acted upon by an external force.
 F = ma, where F is the net force acting on the
object, m is the mass of the object and a is the
acceleration of the object.
 When one body exerts a force on a second body,
the second body simultaneously exerts a force
equal in magnitude and opposite in direction to
that of the first body.
Theory of Plate Tectonics
 The lithosphere is broken up into tectonic plates. On
Earth, there are seven or eight major plates
(depending on how they are defined) and many
minor plates. Where plates meet, their relative
motion determines the type of boundary:
convergent, divergent, or transform. Earthquakes,
volcanic activity, mountain-building, and oceanic
trench formation occur along these plate boundaries.
The lateral relative movement of the plates typically
varies from zero to 100 mm annually.
Science Notebook Reflection
What “rule” could you use to
decide whether a scientific idea
is a theory or a law?
Do a majority of laws or theories
have something in common?