Make two columns on a sheet of paper Make two columns on a sheet of paper. Title 1 column Physical Changes and the 2nd column title Chemical Changes. From the next slide, categorize each item either physical or chemical change.

PHYSICAL OR CHEMICAL Change? Candle wax melting Salt dissolved in water Fireworks exploding Wood burning Leaves changing colors Cooking an egg Cake baking Breaking an egg Cutting paper Ice freezing Water boiling Mixing baking soda and water Iron rusting Tarnished silver Battery corrosion

Chemistry Background In order for elements to be completely stable (or un-reactive) they need to have 8 electrons in their outside energy level. An element with 8 electrons on its last level is a happy element. The “happiest” elements on the table are the noble gases. Exception: Helium is happy with two electrons in its outer energy level.

Selection Process Sodium contains 1 valence electron on its outside shell. It is very unhappy and unstable. It needs a “partner” to balance it out. But, only one type of “partner” will do. It must have 7 valence electrons!

Match Chlorine looks like a good partner because it has 7 valence electrons! Draw a Lewis Dot Diagram for Sodium and Chlorine.

Chemistry of Sodium and Chlorine If sodium gives away its last electron, it will be left with 8 on its last shell! Therefore it will be happy! 1e- 8 2 11P+ positive The sodium atom then becomes a ____________ion.

Chemistry of Sodium and Chlorine If chlorine accepts the electron from sodium it will now have 8 electrons on its outside shell therefore it will be happy! 1e- 7e- 8 2 17P+ negative The chlorine atom then becomes a ___________ ion.

Ion an atom that has an electrical charge because it no longer has an equal number of protons and electrons. 6P+ 6N 2e- 3e-

Rule of Eight 1e- 7e- 8e- 11P+ 17P+ 1e- 8e- 1e- Sodium Chloride

LiF HHe BeO NaCl KI CaS MgO FAr KCl Molecule Possible Not Possible Copy the table and identify if each of the following compounds is possible. Explain why!

Models of Compounds Make the following compounds by fitting the puzzle pieces together. Use the names of the compounds as clues. Sodium chloride Calcium oxide Carbon dioxide Calcium chloride Aluminum oxide Draw the compounds in your notebook and write the name of the compound and its chemical formula. Include the Lewis Dot Diagram for each atom

Chemical Equations Shorthand way that scientists use to represent what takes place in a chemical reaction. Chemical equations consist of many different components (parts).

Components of a Chemical Equation 2Na2O2 + 2H2O -> 4NaOH + O2

Copy the chart and fill in the spaces. Chemical Formula Total # of Elements in the Formula Total # of Atoms in NaCl CO2 H3PO4 2H2SO4 H2O 2C6H12

Symbol Ex: H, Na 1 or 2 letters used to represent an element Place of discovery, scientist, or other language such as Latin or Greek. First letter capitalized, second letter lower case.

Ex: NaCl, H2O Chemical Formula A combination of symbols and numbers that represent the number and types of elements(atoms) present in a compound.

Subscript Ex: CO2, H2O2 Small number written to the right and below the normal line of letters. Shows how many atoms of each element are present in a substance. No subscript means there is only one atom present.

Chemical Reaction Ex: H2 (g) + O (g) H2O (liquid) When substances interact to form one or more new substances with different properties than the original substance

Chemical Equation Ex: 2H2 + 2O2 2H2O2 A combination of chemical formulas used to describe what happens in a chemical reaction. The equation identifies the reactants and resulting products.

Coefficient 2Na + 2Cl 2NaCl A number written in front of a chemical formula to show how many molecules of that substance are present.

Reactants 2CO2 2C + 2O2 Formulas written on left side of arrow ( ) Starting substance or substances in a chemical reaction

Product 2Fe + O2 2FeO Formulas written on the right side of arrow ( ) New substance or substances formed in a chemical reaction

Yields H2 + O2 H2O2 Arrow shows a reaction has taken place. The reactants have reacted to produce a new substance (the product)

Compound H2O, CO2, CO A substance composed of two or more elements chemically combined in a definite proportion

Physical Change A change in which the characteristics of a substance are only changed physically and the original properties stay the same.

Physical properties of matter are characteristics that you can observe about the matter. EX: color, shape, size, density, melting point, boiling point, freezing point, specific heat, state, metal, nonmetal, metalloid, evaporation, condensation, crystallization, conductivity, magnetism, luster, malleability, taste, dissolving, odor, texture, volume, mass, length, temperature Physical Properties

Chemical Changes A change in which a substance or substances is changed into one or more new substances with different properties than the original substances

Chemical Properties Chemical properties of matter are the properties that indicate whether an object can undergo a chemical reaction. EX. flammable, reactive, corrosive, tarnishing, rusting oxidation …

Law of Conservation of Mass Matter is neither created or destroyed, only changed. The number of atoms in the reactants must be equal to the number of atoms in the product.

Precipitate A solid that forms as a result of a chemical reaction It will pull out and fall to the bottom of the container

Law of Conservation of Mass Reactants yields Products NaHCO3 + HC2H3O2 CO2 + H2O + NaC2H3O2 1 sodium, 5 hydrogens, 3 carbons, 5 oxygens BALANCED!!! Number and kind of atoms on the reactant side must equal the number and kinds of atoms on the product side of the equation.

CHEMICAL CHANGES Occur When: Different substances with new properties are formed.

Chemical Equations reactants products You can explain a chemical reaction on paper by using a chemical equation. reactants products What you START with What you end up with yields

Chemical Reactions Involve the breaking or forming of chemical bonds causing atoms to become rearranged into a new substance or substances.

What to look for in a chemical change: New substance with new properties Energy involved (heat being released, heat being absorbed) Gases released Color change A precipitate( a solid that separates out of a reaction)