Chemistry: THE STUDY OF MATTER

So what is matter?

Matter Must have mass Must occupy space (have volume) It is different from weight…..Why? Must occupy space (have volume) A measure of the quantity of matter (it is different from weight, which can be affected by gravity) This volume can change depending on environmental conditions like pressure

Therefore: all matter has a measurable density Density of a Substance = Mass Volume

States of Matter Matter can exist in three basic states: Solid (s), Liquid (l), Gas (g) How are these states different from each other?

Can Matter be Destroyed? Example: When 400 grams of wood are burned only about 30 grams of ash remain. Why does the matter weigh less? What happened to the missing matter?

Law of Conservation of Matter Matter cannot be created or destroyed This was a revolutionary idea up until the 1800’s Ex: Burn a candle, thought part of the candle just disappeared and became nothing. But if you burn it in a closed container you can see the mass doesn’t change as it burns. Matter isn’t being lost but changing in form!

During reactions atoms are all still there, they just get rearranged

Chemical equations are “balanced” with coefficients to obey this law.

Basic Types of Matter

Elements Made of atoms of one specific type Have specific properties. Cannot be broken down further by a chemical reaction

Examples of Elements

Elements and Their Symbols Element symbols are composed of either one or two letters If two letters, the second letter is written lower case. Ex: Write Cu for copper not CU Why is this so important?

Just Read: Usually it is pretty easy to match an element to its symbol (Ex: Neon = Ne) Sometimes the symbol is derived from a Latin name for the element. Ex: Au = gold (comes from Latin word aurum)

Some Tricky Elements Na = sodium K = potassium Fe = iron Cu = copper Sb = antimony Sn = tin Pb = lead Hg = mercury W = tungstun Au = gold Ag = silver

Phases of Elements at STP Gases: H, He, Ne, Ar, Kr, Xe, Rn, N, O, F, Cl Liquids: Hg, Br Solids: All other elements are solids Let’s make a note of these on our Periodic Tables!

Diatomic Elements Composed of two identical bonded atoms Who are they? Note: Most elements are monoatomic in pure form. Who are they? Remember BrINClHOF Let’s make a note of these on our Periodic Tables!

Compounds Two or more different elements bonded together Ex: C6H12O6, NO2, CO2, NaCl Note: Most elements in nature do not exist in their pure state, but in compounds. Why? They are more “stable” that way. The numbers written below the symbols are called “subscripts” and let us know about the number of each type of atom in the compound

Compounds have formulas that show the proportion of elements to each other. Ex: Water is always H2O This is called the “Law of Definite Proportions” Ex: H2O always has 2 hydrogen and one oxygen atom in it

Compounds have different properties than the elements they are composed of. Ex: Sodium (Na) Toxic metal Chlorine (Cl) Toxic gas Sodium Chloride (NaCl) White edible crystal

Focus Question What makes atoms of one element different from another? http://www.pbslearningmedia.org/asset/lsps07_int_theatom/

Atomic Basics Atoms consist of three basic parts. Protons Neutrons Electrons

Fill in Chart: Particle Charge Mass Location Symbol Proton Neutron Electron

Atomic Number: Tells us the number of protons in nucleus It is unique for each element

Atomic Charge Atoms are neutral particles Number of electrons (-) = number of protons(+) How many electrons does an atom of carbon have?

Nuclear Charge Nuclear Charge: What is the Nuclear Charge? the charge on the nucleus of the atom. (+) positive charge = to number of protons What is the Nuclear Charge? What is the Atomic Number? What is this Element?

Ionic Charge Ions: atoms with a charge Protons don’t equal electrons!! Atom has gained or lost electrons Gain electrons: become (-) ion Lose electrons: become (+) ion P = 9 E = 10 What is the element? What is it’s ionic charge?

Ionic Charge Practice Try a few for practice…

Finding the Atom’s Mass Mass Number: Sum of the number of protons + neutrons Each has a mass of 1 amu. (atomic mass unit) Ex: P = 23 N = 21 What is the Atomic Mass Number? What is this element?

Isotopes Isotopes: atoms of the same element with different atomic mass. Same # protons Different # neutrons Ex: Carbon-12, Carbon-13, Carbon-14 How many protons? How many neutrons?

Average Atomic Mass: Atomic mass you see on periodic table Represents the average mass of all the isotopes of an element in a typical sample. Based upon abundance of each isotope and their mass

Calculating Average Atomic Mass Mass of each isotope x abundance (change % abundance to decimal) Add together answers Ex: Chlorine

Crash Course Kids: What is Matter? https://www.youtube.com/watch?v=ELchwUIlWa8&safe=active Crash Course: Atomic Basics https://www.youtube.com/watch?v=FSyAehMdpyI