Warm-Up: Describe the difference between ionic and covalent bonds. You need to list at least 2 differences.

Properties of Covalent Bonds Electronegativity difference < 2. Typically a bond between 2 nonmetals. Do Not Conduct Electricity. Low melting/boiling points. Polar Covalent – unequal sharing of electrons. Non-Polar Covalent – equal sharing of electrons.

Properties of Ionic Bonds Electronegativity difference > 2. Typically a bond between metal and a nonmetal. Conduct Electricity. High melting/boiling points. Anion – negatively charged ion Cation – positively charged ion

Oxidation Number Definition: indicates how many electrons are lost, gained, or shared when bonding occurs. Note: charge is written after the number Aligned with valence electrons Some atoms have more than one oxidation number

Pieces of a Chemical Formula Chemical Symbol: tells us which atoms are present Subscript: tells us how many of each type of atom are present

Chemical Formulas Tell us how many atoms are in each molecule Empirical Formula: simplest whole-number ratios by which elements combine Molecular Formula: actual number of atoms in a compound Could be the same as the empirical formula, or it could have different subscripts For example, if the empirical formula of a compound is C3H8 , its molecular formula may be C3H8 , C6H16 , etc. Charge always equals 0

Writing Formulas Positive ion always comes first, then your negative Na+ Cl- NaCl Naming Formulas: Say the name of your positive ion (sodium) Add –ide to the ending of your negative ion (Chloride) Put them together  Sodium Chloride

Chemical Bonding Worksheet You will work with a partner to complete the worksheet. You will make a model of your atom using Fruity Pebbles as valence electrons. You MUST then draw your atom with its valence electrons and show which electrons are moving or being shared.

Criss-Cross Method Criss-Cross method http://www.youtube.com/watch?v=MNLEe5aIpGQ

Chemical Reactions Write a hypothesis for what you think will happen to a balloon when I mix vinegar and baking soda in soda bottle. Include whether or not you think the reaction will be hot or cold

What Happened? What did you observe? What do you think happened? Take a minute to write down your thoughts. Share with a partner

Physical vs Chemical Change Physical change: affects only the physical properties of a substance. Changes in size, shape, and state. Biting & chewing an apple. Chemical Change: alteration of chemical composition for a substance. Result of a chemical reactions (breaking of bonds in one or more substances and creating new bonds). Enzymes in your saliva breaking down the apple you are chewing so your body can absorb its nutrients.

How do you know a chemical change took place? Formation of a new substance Energy absorbed or released Formation of a gas (release of bubbles)

Recollection of Algebra Take a minute to reflect on everything you know about algebra. This will be different for each one of you. Write down your thoughts and feelings towards algebra in your notebook. What does it look like to you? What is it? Do you like it or not? Does it make sense to you? Why or why not?

Comparing Algebra to Chemistry x + 2 = 6 Chemistry: CH4 + O2  CO2 + H2O What is similar about these expressions? What is different about these expressions?

Comparing Algebra to Chemistry x + 2 = 6 Chemistry: CH4 + O2  CO2 + H2O Similarities They both have 2 sides. Can be written as a sentence with words instead of symbols. Has some sort of symbol that separates both sides of our equation. Uses symbols to stand for something (algebra – variable, chemistry – substance).

Writing a chemical reaction Essentially, a chemical reaction is a sentence written with empirical formulas and an arrow. CH4 + O2  CO2 + H2O Methane reacts with oxygen gas to produce carbon dioxide and water. Note: oxygen gas exists as a diatomic molecule. This means there are 2 oxygen atoms in one molecule of oxygen gas.

Deeper look at Chemical Equations CH4 + O2  CO2 + H2O Reactants Products Reactants: what reacts together in a chemical reaction. Products: what is produced after the reaction is complete.  Usually read as: “yields” or “to produce”