A brief history of Chemistry. Science 9- Mr. Klasz

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1 A brief history of Chemistry Science 9- Mr. Klasz

2 What is a pure substance? An element is a pure substance. A compound is made up of two or more elements which have been chemically compounded together. A compound can be broken down into its individual elements by the way of (complex) chemical changes.

Philosophers: The first to study matter Philosophers, also known

was not necessary; that learning best occurred by thinking not

3 Philosophers: The first to study matter Philosophers, also known as thinkers, wondered why matter behaves the way it does from very early times. These early philosophers believed that hands-on experimentation was not necessary; that learning best occurred by thinking not doing. Ancient Greek philosophers believed that all matter consisted of a combination of fire, air, earth and water.

4 Philosophers cont. Early philosophers also believed that once something had been said to be true, it should be taken as fact. They believed that if it had been recorded it was true, and could not be argued with. This is a complete contradiction to our current views of science!

Alchemists: The first to experiment with matter Alchemists also existed during this time period. For many centuries alchemists performed experiments to learn more about matter.

5 Alchemists: The first to experiment with matter Alchemists also existed during this time period. For many centuries alchemists performed experiments to learn more about matter. They developed some procedures we still use today! Alchemists had a very strong belief that they could turn some elements into other! They thought they could take elements such as lead and convert them into gold. They wrote in their own secret codes so that nobody else could steal their findings.

The start of our current view of matter: Sir Francis

In the early 17 th century, Sir Francis Bacon argued

believed that science should be based on

6 The start of our current view of matter: Sir Francis Bacon Lived from In the early 17 th century, Sir Francis Bacon argued that scientific method should be used to investigate the physical world. In 1620 he published a book which explained why he believed that science should be based on experimentation and not philosophical thinking. This was the first step towards developing the scientific method as we know it today.

Robert Boyle Lived from 1627 to 1691 In 1661, he published The Skeptical Chymist and explained why he believed the four-element theory of ancient philosophers was incorrect.

7 Robert Boyle Lived from 1627 to 1691 In 1661, he published The Skeptical Chymist and explained why he believed the four-element theory of ancient philosophers was incorrect. He said I mean by elements, certain simple unmingled bodies. Boyle also stated that elements can be used to form compounds. However, he did not explain what materials he believed to be elements and which he believed to be compounds. We will revisit Boyle when we look at the atomic theory.

of a chemical change. He identified 23 known pure substances as elements.

Lavoiser stated that it was very important to accurately measure the mass of all

8 Antonie Lavoiser Lived from Defined elements as pure substances that cannot be further broken down by means of a chemical change. He identified 23 known pure substances as elements. He grouped these into metals, non-metals, gases and earth. Lavoiser stated that it was very important to accurately measure the mass of all substances involved in chemical changes. He believed that this was essential to making sound inferences. He is known as the father of modern chemistry.

9 Lavoisier cont. Marie-Anne Lavoiser, Antoine s wife read scientific articles in English and translated those she believed to be of interest to her husband into French for him. Why do you think she was undercredited?

10 Allesandro Volta Lived from Volta created the voltaic pile, also known as a battery. Other scientists started to use this Volta s battery to pass electricity through water. They learned that when electricity was passed through water, the water level dropped and hydrogen and oxygen were released. As such, they discovered that water is composed of hydrogen and oxygen!

11 Humphry Davy Lived from Experimented with passing electricity through other materials to see if other materials then water could be split. He discovered that he needed to start with a liquid mineral or a solution of a mineral to do this. He isolated potassium, sodium, magnesium, calcium, strontium and barium from His assistant Michael Faraday named this electrolysis.

Joseph Proust Lived from 1754-1826 Discovered the law of definite proportions.

12 Joseph Proust Lived from Discovered the law of definite proportions. This is to say that compounds are pure substances containing two or more elements combined together in fixed proportions. For example: Water contains 11% Hydrogen and 89% Oxygen by mass. (H 2 0) Hydrogen peroxide contains 6% Hydrogen and 94% Oxygen by mass. (H 2 O 2 )

All atoms of the same element are identical in mass and size, but they are different in

13 John Dalton Lived from Dalton wrote an atomic theory which contains 4 postulates: All matter is made up of small particles called atoms. Atoms cannot be created, destroyed, or divided into smaller particles. All atoms of the same element are identical in mass and size, but they are different in mass and size from the atoms of other elements. Compounds are created when atoms of different elements are linked together in definite proportions. He wrote this theory to provide a way to explain chemical facts and define the word element.

The definition of an element Dalton wrote his atomic theory to define what an element is. His theory was based upon his own research and the research of others for the past 100 years.

14 The definition of an element Dalton wrote his atomic theory to define what an element is. His theory was based upon his own research and the research of others for the past 100 years. Element: A pure substance made up of one type of particle, or atom. Each element has its own distinct properties and cannot be broken down into simpler substances by means of a chemical change.

15 Law vs. Theory A law does not explain anything; it simply describes what happens. A theory is a way of explaining what happens. Theories are discussed, debated and challenged repeatedly.

The history of the concept of element, with particular reference to Humphry Davy

The history of the concept of element, with particular reference to Humphry Davy One of the problems highlighted when the recently implemented chemistry syllabus was being developed was the difficulty