1. Science Starter (Week 15, Day 1, 5/9/16)
Turn in Poster Book to bin!
HW 7.3 ON DESK
Grab a calculator!
For each of the following state the number of steps and equation to use in each step:
How many grams of ice will melt at 0˚C if the ice absorbs 420J of energy?
An ice cube tray full of ice (235g) at –7.0˚C is allowed to warm up to room temperature (22˚C). How much energy?
A serving of Cheez-Its releases 130J when digested by your body. If this same amount of energy were transferred to 2.5 g of water at 27˚C, what would the final temperature of the water be?

2. Objective
SWBAT describe reactions as either endothermic or exothermic based on information about temperature, products/reactants, etc.
SWBAT identify and explain all major parts of a potential energy diagram

3. Weekly Schedule Monday: Endothermic & Exothermic, Potential Energy
Tuesday: Laws of Thermodynamics
Wednesday: Phase Change Diagrams, Dry Ice Lab
Thursday: Unit 7 Review
Friday: Unit 7- Heat & Energy Test

4. Agenda Science Starter Notes Exit Ticket Endothermic and Exothermic
Potential Energy Diagrams
Exit Ticket

5. Unit 7: Heat and Energy Endothermic/Exothermic Reactions

6. HC2H3O2 + NaHCO3 + ENERGY NaC2H3O2+ NaCl +H2O
EXOTHERMIC (energy EXits the system)
Thermal energy is released from the system  feels warm or hot
Energy is part of the PRODUCTS.
CH4 + 2 O2  CO2 + 2 H2O + ENERGY
ENDOTHERMIC (energy goes INTO the system)
Thermal energy from is absorbed during the rxn  feels cold!
Energy is part of the REACTANTS.
HC2H3O2 + NaHCO3 + ENERGY NaC2H3O2+ NaCl +H2O

7. Determine whether it is ENDOTHERMIC or EXOTHERMIC.
Quick Check
Determine whether it is ENDOTHERMIC or EXOTHERMIC.
The reaction feels cold to the touch.
Energy is a reactant of the equation.
Energy is released into its surroundings.
The reaction feels hot to the touch.
CH4 + 2 O2  CO2 + 2 H2O + energy
Energy is absorbed into the bonds.

8. Unit 7: Heat and Energy Potential Energy Diagrams

9. Law of Conservation of Energy: Energy can neither be… Potential (Chemical) energy = energy stored in chemical bonds Every chemical reaction has ENERGY associated with it. You can show this change in energy with a POTENTIAL ENERGY DIAGRAM. NOTE!!!! We measure energy in “kilojoules”, just like we measured mass in grams and volume in Liters.

10. New Terms!!
Activation Energy: Energy required to start a reaction (to get up the hill).
Heat of Reaction (ΔH): Energy absorbed or released during a reaction. ΔH = H products – H reactants -ΔH = Exothermic +ΔH = Endothermic
Activated Complex: The peak of the curve. The maximum energy in the reaction.

11. Potential Energy Diagram
 Follow along with what I label on the board

12. Practice Questions:
What is the ACTIVATION ENERGY of the reaction in our P.E.D.?
What is our ΔH?
Is this reaction exothermic or endothermic? How do you know?
What would be the REVERSE ACTIVATION ENERGY (if the reaction went backwards from products back to reactants)?
Would the reverse reaction be exothermic or endothermic?

13. Catalyst
A catalyst lowers the activation energy of both the forward and reverse reactions equally. We therefore shorten the reaction pathway and the reaction will speed up.
 What will this look like on the diagram??
Your blood contains a catalyst!! What is an everyday substance that reacts as soon as it comes in contact with your blood, but not when it is just left alone?

15. Poster Making Contest
I will assign you to a group to make a potential energy diagram. Your poster should include ALL KEY VOCABULARY from the notes. You must also include:
Units on graph
Explanation of whether your reaction is endothermic or exothermic
The group with the most informative and beautiful poster will receive 4 EC points on Friday’s test.

16. John, Christabel, Monashya Trey, Ruth, Tonasia Joel, Shadiya, Taia
Groups
John, Christabel, Monashya
Trey, Ruth, Tonasia
Joel, Shadiya, Taia
Jamal, Joy, Abel
Alvin, Asia, Samantha

17. Practice Worksheet
Spend the remaining time completing the worksheet on the back of the diagram.