The Scientific Method

Scientific Method

• Scientific Method• Scientific Law• Scientific Method and Law• Theories and Laws• Why Dinosaurs Disappeared• The Hellenic Market• Four-Element Theory• Drunken Goldfish• Science and Morality

Using the scientific method requires that one be a good observer.

observation inference

involves a judgmentor assumption

uses the fivesenses

The Skeptical Chemist

Robert Boyle

Published “The Sceptical Chymist”

…stated that scientific speculationscientific speculation was worthless unless it was supportedby experimental evidenceexperimental evidence.

This principle led to the development of the scientific methodscientific method.

(in 1661)

“My mother the eye doctor”

Observation or Inference?

One player is holding a bat.The player holding the bat is talking.One of the teams is called the “Reds.”One player is wearing a catcher’s mask.One player is a catcher.Names are written on the uniforms.The players in the picture are on opposite teams.The adult is the umpire.The piece of paper is a note from the mother of the batter.The adult is holding a piece of paper.The mother of the batter is an optometrist or opthalmologist (an eye doctor).

DataObservations are also called data.

There are two types of data.

qualitative data quantitative data

descriptions; measurements; no numbers must have numbers

Parts of the Scientific Method

• Identify an unknown.• Make a hypothesis

(a testable prediction).• Experiment to test

the hypothesis.• Draw a valid conclusion.

A Scientific Experiment

procedure

the order of events

in an experiment;

the “recipe”

Experiments must be controlled; they

must have two set-ups that must differ

by only one variable.

The conclusion must be based on the data.

variable

any factor that

could influence

the result

A Controlled Experiment?

Scientific Method

• Observations• Hypothesis• Experimentation

– Controlled (one variable changed at a time)– Collect data (quantitative and qualitative)– Analyze data (graph, statistics…trends)

• Form valid conclusion.

• After many experiments…form a theory.

Scientific Law vs. Scientific Theory

Law of Gravity

A theory tries to explain why

or how something happens.

A law states what happens.

Theory of Gravity

Atomic Theory

Collision Theory of Reactions

Theory vs. Natural Law

Scientific theory Natural law

Experiment

Hypothesis

analyze additional data

analyze initial observations

Make observationMake observation

Ask questionAsk question

Develophypothesis

Develophypothesis

Test hypothesis with an

experiment

Test hypothesis with an

experiment

Analyze dataand draw

conclusions

Analyze dataand draw

conclusions

Hypothesis IS

supported

Hypothesis IS

supported

Hypothesis is NOT

supported

Hypothesis is NOT

supported

Developtheory

Developtheory

Test hypothesis with furtherexperiments

Test hypothesis with furtherexperiments

Revisehypothesis

Revisehypothesis

Wysession, Frank, Yancopoulos, Physical Science Concepts in Action, 2004, page 8

Scientific Method

Results confirmed by other scientists –validate theorytheory.

Data do not supporthypothesishypothesis – revise or reject hypothesis

Stages In The Scientific Method

OBSERVING

•collecting data•measuring•experimenting•communicating

TESTING

•predicting•experimenting•communicating•collecting data•measuring

THEORIZING

•constructing models•predicting•communicating

PUBLISHRESULTS

•communicating

FORMULATINGHYPOTHESES

•organizing and analyzing data•classifying•inferring•predicting•communicating

Reviewing ConceptsWhat is Science?

• How does the scientific process start and end?

• How are science and technology related?• What are the branches of natural science?• Explain the advantages and disadvantages

of subdividing science into many different areas.

• Why do scientists seek to discover new laws of the universe?

Reviewing ConceptsUsing a Scientific Approach

• What is the goal of scientific methods?

• How does a scientific law differ from a scientific theory?

• What are scientific models useful?

• What are three types of variables in a controlled experiment?

• Does every scientific method begin with an observation? Explain.

Scientific Law

Laws of nature never change.

Charles’sLawV

1 V2T1 T

2

=

Theories and Laws

The Earth is flat…

Speeding kills (Audubon, Germany);

No explanation of why…but the theorytheory is if you drive at 120 mph and crash, an ambulance won’t need to be called (only next of kin).

seat belts save lives…LAWLAW: 65 mph and wear seat

belt

Why Dinosaurs Disappeared

Dinosaurs MeteorEarth Dust Cloud

Moon is formed

Ice Age - Glaciers

RIPMeteor Crater

Sun blocked

Evidence…

A theory…

The Original Metric Reference

H2O H2O= 1 meter = 1 kilogram = 1 liter

Length Mass Volume

1 kg

1/10 m

1/10 m

1/10 m

1/10,000,000

The Hellenic Market

Fire Water Earth Air

~~

Four Element Theory

• Plato was an atomist

• Thought all matter was composed of 4 elements:– Earth

– Water

– Fire

– Air

– Ether (close to heaven)

‘MATTER’

FIRE

EARTHAIR

WATER

Hot

WetCold

Dry

Relation of the four elements and the four qualities

Scientific Method and Law

Combustion & Phlogiston

• Phlogiston Theory• Combustion Theory• Burning Magnesium Metal in an Open Container• Burning Magnesium Metal in a Closed Container• Lighting a Bunsen Burner• Flame Temperature Distribution

Phlogiston Theory

(a) When an object burns

it gives off a substance

called phlogiston.

(b) When the space surrounding

the burning object is filled with

phlogiston, the object will no

longer be able to burn.

Phlogiston theory of burning

Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 4

Combustion Theory

Modern theory of burning

(c) When an object burns, it uses

up a substance (oxygen) in

the surrounding space.

(d) When the space surrounding

the burning object has too little

oxygen in it, the object will no

longer be able to burn.

Antoine Lavoiser

Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 4

Phlogiston Theory of Burning

1. Flammable materials contain phlogiston.

2. During burning, phlogiston is released

into the air.

3. Burning stops when…

…object is out of phlogiston, or

…the surrounding air contains

too much phlogiston.

Burning Magnesium Metal in an Open Container

Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 77

Burning Magnesium Metal in a Closed Container

Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 77