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Compounds and Compounds and ElementsElements
Breaking it DownBreaking it Down
Compounds and ElementsCompounds and Elements
Compounds are pure substancesCompounds are pure substances They are made up of two or more elements They are made up of two or more elements
chemically bound together.chemically bound together.
So what are elements??So what are elements??
The Elements - a brief historyThe Elements - a brief history
For thousands of years people wondered For thousands of years people wondered why matter behaved the way it did.why matter behaved the way it did.
““What is everything made of?”What is everything made of?”
““Why does water freeze?”Why does water freeze?”
““What am I made of?”What am I made of?”
The Elements - a brief historyThe Elements - a brief history
Philosophers spent a Philosophers spent a lot of time lot of time thinking thinking and talkingand talking about about matter but very little matter but very little time doing anything time doing anything with it.with it.
I don’t want to get my hands dirty!
The Elements - a brief historyThe Elements - a brief history
For centuries scientists and philosophers For centuries scientists and philosophers believed that all matter was made up ofbelieved that all matter was made up of
EarthEarth AirAir FireFire WaterWater
Earth Wind and FireEarth Wind and Fire
When they look likethis….
Not these guys !
I looked likethis….
Ahhh….the ‘70s
The Elements - a brief historyThe Elements - a brief history
This view of This view of all matter all matter being made being made up of only up of only four four elements elements lasted until lasted until the 17th the 17th century in century in Europe,Europe,
AlchemistsAlchemists
While philosophers were thinking about matter, While philosophers were thinking about matter, AlchemistsAlchemists were doing something about it. were doing something about it.
Believed that one element could be changed into Believed that one element could be changed into another.another.
Part Chemist , Part MagicianPart Chemist , Part Magician
Lead Gold
AlchemistsAlchemists
Alchemists did all sorts of hands-on Alchemists did all sorts of hands-on chemistry.chemistry.
They did many experiments and discovered They did many experiments and discovered many things.many things.
They were very secretive and developed a They were very secretive and developed a secret code to keep track of their secret code to keep track of their experiments.experiments.
Sir Francis BaconSir Francis Bacon1561 - 16261561 - 1626
In the 17th century Francis In the 17th century Francis Bacon wrote a book that Bacon wrote a book that changed the way people changed the way people thought about science.thought about science.
Bacon asked people to let go of the old way of looking at science
He developed the scientific method.
Convinced people that science should be based on experimental observation, not just thought.
Robert BoyleRobert Boyle1627-16911627-1691
First scientist to express publicFirst scientist to express public
skepticism of the “four elements” view of matter.skepticism of the “four elements” view of matter.
Called elements “unmingled bodies”.Called elements “unmingled bodies”. Recognized that elements could be combined to Recognized that elements could be combined to
form compounds.form compounds.
Breaking it down…Breaking it down…
In the 17th century scientists got very In the 17th century scientists got very excited about breaking matter apart until it excited about breaking matter apart until it couldn’t be broken apart anymore.couldn’t be broken apart anymore.
These elemental parts are called elements.These elemental parts are called elements.
They heated, burned, cooled and mixed They heated, burned, cooled and mixed everything they could get their hands on to everything they could get their hands on to see how things could be broken down.see how things could be broken down.
The Mad Scientist Was BornThe Mad Scientist Was Born
Antoine LavoiserAntoine Lavoiser1743 - 17941743 - 1794
Lavoiser was a pioneer in this field.Lavoiser was a pioneer in this field.
He identified 23 new elements by breaking things He identified 23 new elements by breaking things down into the smallest parts.down into the smallest parts.
Realized that measuring the mass of all parts of a Realized that measuring the mass of all parts of a chemical reaction was essential to making inferences chemical reaction was essential to making inferences about what was happening in chemical reactions.about what was happening in chemical reactions.
Volta!!Volta!!
In the 19th century a In the 19th century a new investigative tool new investigative tool was invented - the was invented - the Voltage PileVoltage Pile..
Invented by Allesandro Invented by Allesandro VoltaVolta
Essentially - a Essentially - a batterybattery..
Voltage PileVoltage Pile
The voltage pile was much like a battery.The voltage pile was much like a battery. Delivered a reliable supply of electric Delivered a reliable supply of electric
current.current. What did scientists do first?What did scientists do first?
Stick It Up Their Nose?Stick It Up Their Nose?
Eat it?Eat it?
Nope! They did Nope! They did something way cooler.something way cooler.
They immediately began passing current They immediately began passing current through water… and what do you think through water… and what do you think happened?happened?
Making Gas….Making Gas….
They found that They found that a)a) hydrogen and oxygen gases were produced.hydrogen and oxygen gases were produced.
b)b) the water level fell slightlythe water level fell slightly
Hmmm………..
Inferring….Inferring….
They inferred that some of the water had They inferred that some of the water had been decomposed into hydrogen and been decomposed into hydrogen and oxygen.oxygen.
So if that works….So if that works….
Humphry Davy Humphry Davy (1778-1829) (1778-1829) wanted to see what wanted to see what else could be decomposed using electricity.else could be decomposed using electricity.
Using Current…Using Current…
Davy discovered…Davy discovered… PotassiumPotassium SodiumSodium MagnesiumMagnesium Calcium Calcium BariumBarium StrontiumStrontium
Davy found that he had to start with a liquid mineral or a solution of a mineral.
His assistant, Mike Faraday called this process electrolysis.
Not this kind of electrolysisNot this kind of electrolysis
This kind…This kind…
Law of Definite PorportionsLaw of Definite Porportions
Compounds are pure substances that Compounds are pure substances that contain two or more elements combined contain two or more elements combined together in fixed or definite amounts.together in fixed or definite amounts.
So… if you have 300 units of water you will So… if you have 300 units of water you will have 200 units of Hydrogen and 100 units of have 200 units of Hydrogen and 100 units of Oxygen. Oxygen.
Because of the difference in weight…Because of the difference in weight…Water = 11% Hydrogen + 89% oxygenWater = 11% Hydrogen + 89% oxygen
Law of Definite PorportionsLaw of Definite Porportions
Hydrogen peroxide contains H and O but in Hydrogen peroxide contains H and O but in different proportions…different proportions…
6 % Hydrogen + 94% Oxygen6 % Hydrogen + 94% Oxygen
These proportions always hold true.These proportions always hold true.
Properties of CompoundsProperties of Compounds
Pure substances have constant compositionPure substances have constant composition They also tend to have constant properties - They also tend to have constant properties -
they tend to always behave the same way.they tend to always behave the same way. We can use these constant properties to We can use these constant properties to
identify the element…identify the element…
How might you do this?How might you do this?
One more thing…One more thing…
Law of Conservation of MassLaw of Conservation of Mass In a chemical change, the total mass of the In a chemical change, the total mass of the
new substance is always the same as the new substance is always the same as the total mass of the original substances.total mass of the original substances.
What goes in gotta come outWhat goes in gotta come out
