02/03/15 O To Do: O Bell Work O Hydrated Crystal Lab O Bonding O Chemical Reactions O Practice WSs O Complete foldable for Ch. 8.2 – Types of Chemical Reactions O Bell Work: O Copy To Do list in Agenda. O Note Quiz – complete the handout and return to Ms. M.

Announcements O Foldable O Procedure Changes: O No more test corrections, but retakes will be available. O Students who have a C- or below will receive after school detention on Thursdays to provide time for improvement (assignment corrections, test retakes, complete missing work, etc.). O You, your parents, and the administration will be notified. O No Late Work without Mac Pass! O You have 4 for the semester, use them! O Complete them well, or you don’t get full credit. O May not use the last two weeks of the quarter.

Hydrated Crystal Lab

Chemical Equations O Notes will go on pg. 70 of your SIN. O Remember to set up Cornell notes!

Ionic Bonds O What is the force behind an Ionic Bond? O Attractions of positive and negative ions. O Charged atoms what to be neutral, so they are attracted to each other. O These bonds are much harder to break in a chemical reaction.

Covalent Bonds O What causes a covalent bond to form? O The sharing of electrons to get to the happy number, 8 valence electrons. O Hydrogen is the exception, as it is happy with 2 valence electrons. O Why is hydrogen happy with 2 valence electrons? O Hint: look at his electron orbitals. O How do we figure out how atoms will bond covalently?

Covalent Bonds O How do we figure out how atoms will bond covalently? O We draw Lewis dot diagrams. O Look at water to the left: O Oxygen is sharing electrons so it has 8 electrons. O Hydrogen is sharing 2 electrons. O Both are happy. O Looking at these diagrams, what do you know about the number of electrons shared by atoms?

Covalent Bonds O Lewis Dot Diagrams will tell show where shared electrons will go – look at the diagram to the right. O CO 2 – Carbon is sharing 8 electrons and oxygen is sharing 4 electrons to go with the 4 it has to get to the happy number of 8. O The second diagram shows that we can use bars to represent a pair of shared electrons.

Covalent Bonds O Covalent bonds can have multiple shared pairs of electrons. O They will be referred to as follow: O Single Bond if it is like the water molecule – one pair of electrons shared between atoms. O Double Bond if it is two electrons pairs shared between atoms. O Triple bond if it is three electron pairs shared between atoms. O Etc.

Bonds and Chemical Reactions O Why is it important to know about bonds when we discuss chemical reactions? O Tells you the amount and type of energy you will get. O Ionic bonds are hard to break, taking more energy. O Covalent bonds are easier to break, so less energy is required. O You also need to know how atoms will rearrange in your chemical equations.

Physical Indicators of Chemical Reactions O Evolution of energy as heat & light O Heat and/or light is given off when two compounds are mixed. O Color change O Production of gas O Formation of a precipitate O Precipitate – when a solid is produced in a solution from a chemical reaction.

Chemical Equations O A chemical reaction is when the atoms of one or more substances are rearranged to form a new substance. O Reactants are your starting material. O Products are your ending material. O What are the reactants and products in the equations to the right?

Chemical Equations Symbols

Chemical Equations O Diatomic Compounds – Look up a definition in your book! O Why do we need to keep this in mind?

Chemical Equations O Word problems will state what is happening in a chemical reactions: O 2 g of sodium is reacting with 2 mL of chlorine to form sodium chloride. O What would the chemical equation look like? O Remember: O Starting material goes on the left. O Ending material on the right. O Use a + sign to indicate something is mixing. O Separate with an arrow pointing in the direction the reaction takes place. O Energy required it placed over the arrow. O You should list the state of the compound; (s), (g), or (l)

Chemical Equations O Balancing Equations: O Remember Conservation of Mass – the law that says mass is either created or destroyed. O What you start with must be what you end with. O If you have 4 hydrogen atoms, you must end with 4 hydrogen atoms.

Chemical Equations O Balancing Equations: O Word problem: methane gas (CH 4 ) and oxygen are mixed to make carbon dioxide and water. O What would the equation look like?

Chemical Equations O Take what we know about chemical formulas to figure out how the mass was calculated below.

Chemical Equations O Balancing Equations: O You have your equation: CH 4 + O 2 CO 2 + H 2 O O Is this equation balanced?

Chemical Equations O Balancing Equations: O You have your equation: CH 4 + O 2 CO 2 + H 2 O O Is this equation balanced? O No, because if we compare the number of atoms of each type on each side, they are not equal. Below is the correct equation.

Chemical Reactions To Do List O Review Ch. 8.1 in your textbook. O Add any details you think are needed. O Complete your left column, added color and write a reflection: O How is this related to what we have learned? O How is this going to help with what we have left to learn?

Chemical Reactions Practice O Practice balancing equations: O Both worksheets will be taped to pg. 69 of SIN. O Remember to ask for help as I come around.