4. Theories and laws

An introduction to these terms by PBS


The term ‘science’ comes from the Latin Scientia, which means ‘a knowledge based on demonstrable and reproducible data’. Reproducible data is used by scientists to develop theories and laws to explain and describe phenomena. Theories provide a coherent understanding of a wide range of phenomena. A law is usually a statement that can be expressed as a mathematical relationship. It describes phenomena in nature, with no exceptions, at a point in time. Testing scientific theories drives scientific breakthroughs and questions current understandings.

Students examine how complex models and theories often require a wide range of evidence, which impacts on society and the environment. In this module, students engage in practical and secondary investigations that are related to major theories or laws and their application.

Introduction to Scientific Theories and Laws

Inquiry question 1: What are the differences and similarities between scientific theories and laws?

A Venn diagram is a good tool to use to compare and contrast concepts.

Comparing theories and laws

Investigate Laws and theories


1. The law of conservation of mass ( primary data) 

Investigate the law of conservation of mass ( primary data) and a click view video part D that talks about the discovery of atoms, including many experiment demonstrations.

2. The theory of plate tectonics ( secondary data) 

Investigate the theory of plate tectonics ( secondary data) and a click view video about the discovery of plate tectonics and more information from the Geological Society. 

Development of a Theory

Inquiry question 2: What leads to a theory being developed?

“Just a Theory”: 7 Misused Science Words

Theories are accepted with supporting evidence 

Gather secondary-sourced data to investigate the supporting evidence and development of theories, including but not limited to;

  1. Germ theory 

2. Oxygen theory of combustion

Theories can be disproven with new evidence

A good introduction video from YOUTUBE summarises some ways that various theories have been disproven including the Phlogiston theory, Steady state theory, Spontaneous generation and the Contracting Earth model.

Gather secondary-sourced data to investigate how aspects of a theory can be disproved through the collection of evidence, including;

  1. Geocentric theory

2. Theory of inherited characteristics 

   3. Daltons atomic theory 

4. Steady-state theory of the universe

Development of Laws

Inquiry question 3: What leads to the acceptance of a scientific law?

Secondary data can support scientific laws 

Gather secondary-sourced data to investigate and assess the evidence that supports scientific laws, including but not limited to:

1.Newton’s Second Law of motion ( physics)

2.Avogadro’s law (chemistry)

3.Law of superposition ( Earth science) 

4. Mendel’s Law of dominance ( biology)

Experiment results can be predicted using scientific laws

Design and collect primary data to show that results can be predicted by laws, including but not limited to:

1.Ohm’s Law 

2. Law of conservation of energy 

Law of conservation of energy, see below for more investigations relevant to different fields of science.

The Newtons cradle is often used to demonstrate the Law of Conservation of energy.

Application of Theories and Laws in Science

Inquiry question 4: How are theories and laws used in science?

Investigating the law of conservation of energy

 Video introduction: An excellent series called Shedding light on energy from Clickview.This series of 3 clips contains lots of information and practical examples from all disciplines of science relating to energy and energy transformations.

Investigate how the law of conservation of energy is applied in different science disciplines through primary and secondary-source research, including but not limited to;




  • Human Biology( more on the conservation of mass than energy, however, the energy would be transferred to chemical bonds that are broken and reformed)

Earth and environmental science

Unifying theories

Demonstrate, using evidence and examples, how diverse phenomena have been unified into specific theories, for example:

Unifying the conservation of law and mass 

Gather secondary-sourced data to investigate how scientific investigations of nuclear reactions and decay changed the way in which the law of conservation of mass and law of conservation of energy is interpreted.