Theories and Laws

Hypotheses, Theories, Laws Part II

By Heidi Whitcher

A theory is a well tested, widely accepted explaination that combines several hypotheses and observations.

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*Can predict what may happen in the future.

*Can be modified or replaced based on new information or technology.​

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Kinetic Molecular Theory: All matter is made up of atoms that are constantly moving.

​Theories

Multiple Select

Which statements correctly describe theories? Check all that apply

• Theories result from several repeated experiments

• Theories cannot predict what may happen in the future

• Theories explain observations and hypotheses

• Theories may be revised over time.

A law is a statement about how something behaves or functions in the natural world.

*Is based on observations

*Does not explain observations

* Is a factual statement

*Cannot be changed or replaced.​

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Newton's first law of motion

​Laws

Multiple Select

Which statements correctly describe laws? Check all that apply.

• Laws are created based on repeated experimentation.

• Laws are based on observation.

• Laws can be changed or replaced.

• Laws are factual statements

What is the relationship between hypotheses, theories, and laws?

*Hypotheses come from scientific questions, are based on prior knowledge or research, and must be testable.

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*Theories explain hypotheses and observation.​ Theories may be changed over time.

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*Laws describe how things behave or function.​

Theories are based on repeated experimentation.​

Experimental methods change​

New Methods provide new information​

Theories are changed or replaced​

Atomic Theory

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*400 BCE- Democritus coined the term atomos for atmos

*1780s- Lavoisier developed the law of conservation of mass.

​*1803-Dalton developed the first atomic theory of matter

*1897- Thomas discovered electrons

*1911- Rutherford discovered the nucleus

1913- Bohr found evidence that electrons are arranged in energy levels.

1926- Schrodinger's work led to the electron cloud model.

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Atomic Theory: All substances are composed of tiny particles called atoms.

Multiple Select

Explaining why theories change

For what reasons could a theory be changed or replaced? Check all that apply.

• New technology is developed that provides more information about the theory.

• New experimental methods are designed to test a theory

• A new, untested hypothesis is proposed

• New information is discovered that does not support the theory

​Check out some of these developments in atomic theory

• Cathode Rays Lead to Thomson's Model of the Atom - YouTube

• ​The Discovery of the Atomic Nucleus (3 of 15) - YouTube

• Discovery of neutron - YouTube ​