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Matter Anything that has mass & takes up space So matter is??? Maybe it is easier to ask Democritus’s View • Democritus (460 B.C. – 370 B.C.) – Greek philosopher – Thought the universe was made of empty space & tiny bits of stuff – He called the tiny bits of stuff “ATOMS” – He defined atoms were so small, that they could no longer be divided – The word atom means “Cannot be divided” – This is where WE got the word ATOM What we call an atom! • Do we completely agree with Democritus? • WE DIDN’T until the early 1800s • Scientists built upon his idea to form the current “Atomic Theory of Matter” • We currently define an atom as “a small particle that makes up most types of matter” = Lavoisier’s Idea • French Chemist (2,000 years AFTER Democritus) – Came up with the Theory of Conservation of Matter • Which states that matter is neither created or destroyed –it only changes form Forest PLUS Forest Fire Equals ASHES Answer Atomic Theory of Matter • John Dalton, an English school teacher from the early 1800s, came up with the idea • Atoms are incredibly small particles that have the properties that give the item they make up their properties – Gold behaves like gold, because its atoms behave this way Gold So…. How big is an atom?? So…. How big is an atom?? The Basic Unit of Matter is Atomic Structure • The center of the Atom is called the Nucleus – It is about 100,000 times smaller than the entire atom – It makes up 99.9% of the mass of the atom In the Nucleus • There are two Subatomic Particles – 1. Proton: Which is a positively charged particle – 2. Neutron: Which is a neutrally charged particle » These 2 subatomic particles are nearly equal in mass Is that it?? • There is one final subatomic particle in an atom • This is called an Electron • Electrons have a negative charge • They are also not located IN the nucleus • They travel throughout the atom at high speeds • They are EXTREMELY tiny (With the mass equal to about 1/2000 of a proton and neutron) Atomic Model vs. Electron Cloud • An incredible number of experiments have been done to try to understand the way an atom looks and functions • Currently we have two ways of looking at the structure of an atom – The right way…. And the wrong way! The Wrong (But Easier) Way • Modern Atomic Model – Shows electrons orbiting the nucleus of an atom like planets around the sun – This is what we commonly think of when we think of an atom – It places each electron in its own (or sometimes a shared) orbit – Until just recently, we thought this to be correct New Model • As science is forever changing, a new theory has arose to explain atomic structure • This is called the Electron Cloud Theory • This states that electrons move around the nucleus in an undefined cloud shaped like a sphere • This places the electrons in areas similar to an orbit, where they are more likely to be # of Electrons vs. Protons • In a normal atom there will be THE SAME number of Protons (+) and Electrons (-) – This makes a Neutral Atom • However, sometimes an atom is charged! • If it has a negative charge, it will have more electrons(-) than protons(+). • If it is positively charged, it will have more protons(+) than electrons (-). Examples • So if an atom has 3 extra protons, it would have a charge of what?? • +3 • If an atom had a charge of -2, what does it look like? • It has 2 extra electrons • If an atom has 2 extra protons and 3 extra electrons it will have a charge of what?? • -1 Properties of H2O • Hydrogen bonds: Because water is a polar molecule it can form up to 4 hydrogen bonds • This allows water to have certain properties: – Cohesion is the attractive force between molecules of the same substance • This allows water to stick to itself – This is why water beads on a window – This is why some organisms can stand on top of water – Adhesion is the attraction between molecules of different substances • This allows for water to stick to other things – This is why water moves up the xylem of a plant Van Der Waals Forces • When molecules are close together, a slight attraction can occur between the positively and negatively charged regions of nearby molecules – This doe not require the molecules to have a specific or complete charge • THIS HAPPENS WITH WATER Atomic Number • The number of protons not only tells you what the positive charge is, it also tells you of the atoms atomic number. • Its atomic number tells you what Element the atom is • An Element consists of entirely ONE type of atom • There are only 109 different elements • 90 of which are found in nature • 19 were created in a lab Periodic Table of Elements • • • • Why do we need one? What is the point of classifying things? Does it speed things up? Do you think it was easy to make? Changing Your Numbers • Changing the number of Protons changes your element • Changing your number of electrons changes your charge to negative or positive • What happens if you change the number of Neutrons???? Isotope • When you change the number of Neutrons in an atom you get what is called an Isotopes & a Mass Number • Every element on the periodic table has a specific Mass Number • This number indicates the mass of the atom • The mass comes primarily from the protons & neutrons in an atom • Therefore, having a different number of neutrons (Isotope) will change the mass number • Isotopes are represented by adding the mass number to the atom symbol Numbering & Isotopes Other Things to Know About Atoms • • • • • Chemical formulas Radioactive isotopes Ionic Bonds Covalent Bonds Chemical vs. Physical properties Solids • Have a definite shape and volume • Are Solids moving? • The atoms in a solid vibrate, but keep the same shape and volume • Atoms are packed closely together Liquids • Has definite volume, but no definite shape • Has Viscosity – The strength of attraction between the particles of a liquid – Causes a liquid to move slowly • Like molasses or honey • Will also have a surface tension – This often results from hydrogen bonding or very high viscosity Gas • Have No definite shape or volume • Particles are much further apart • They will often spread out evenly, trying to be as far apart form each particle as possible • Gas or air pressure results from forcing the particles closer and closer together Energy • Why can’t we increase a liquids energy endlessly? • When you boil water, does the temperature remain constant? • If the stove top reaches a temperature of 250 degrees Celsius, is the water also 250 degrees Celsius • Why does water bubble when it boils? Energy • Energy is the ability to do work or cause change • The energy of motion is called KINETIC ENERGY • Particles with more kinetic energy move Faster & are further apart • The total energy of all the particles in a sample of matter is called Thermal Energy Temperature • The average kinetic energy of the individual particles is called the Temperature • The amount of heat required to raise the temperature of a substance 1 degree Celsius is called its Specific Heat • Substances with a low specific heat, such as metals, heat up quickly • Does water have a low or high Specific Heat? Back to the Oranges • Again, think of oranges… • But this time, think of them on the tree Question!? • When the fall nights approach freezing in Florida, farmers come out and spray the orange trees with water…… • ……………….WHY?? Answer!! • Water has a higher specific heat than orange juice • Therefore an orange can freeze at temperatures above 0 degrees Celsius • The water would then act like a blanket for the orange, keeping the temperature up. • Also, when the water begins to freeze, it can protect the juice inside the orange for a limited amount of time, in the same way ice protects a lake Vaporization • When liquid turns into gas • Also called evaporation • The temperature during vaporization does not change • Not only temperature, but pressure also affects this • The evaporating molecules MUST be at the surface too Condensation • The opposite of vaporization • A gas turning to liquid • Heat is lost from the vapor and it changes form into a liquid • Think of water on a cold glass on a hot summer day….Where did it come from?