Chemistry B 6.2 Assignment Energy Changes in Chemical Reactions ... - Free Printable

Here are the answers to the questions in Part I of your assignment.

1. Define what each of the pre/suffix means below.
* a. Therm: Heat or temperature.
* b. Endo: Inside or within (absorbing).
* c. Exo: Outside or external (releasing).

2. There is a change in heat what types of reactions occur?
Chemical reactions occur. Specifically, these are classified as either endothermic or exothermic reactions depending on whether heat is absorbed or released.

3. Describe what happens to the energy in an exothermic and endothermic reaction.
* Exothermic: Energy is released into the surroundings (usually as heat or light). The products have less energy than the reactants.
* Endothermic: Energy is absorbed from the surroundings. The products have more energy than the reactants.

4. Sketch or draw an energy diagram showing what an exothermic reaction looks like.
*(Since I cannot draw, here is a description of how to sketch it based on the first graph in your image)*:
Draw a graph with "Energy" on the vertical axis and "Reaction Progress" on the horizontal axis. Start with a line for Reactants at a higher level. Draw a curve that goes up slightly (activation energy) and then drops down significantly to a lower level for the Products. The final line should be lower than the starting line.

5. Sketch or draw an energy diagram showing what an endothermic reaction looks like.
*(Based on the second graph in your image)*:
Draw a graph with "Energy" on the vertical axis and "Reaction Progress" on the horizontal axis. Start with a line for Reactants at a lower level. Draw a curve that goes up high (activation energy) and then comes down slightly to a higher level for the Products. The final line should be higher than the starting line.

6. Describe activation energy and why it is important in chemical reactions.
Activation energy is the minimum amount of extra energy required by reactant molecules to become product molecules. It is important because even if a reaction releases energy overall, you still need a "push" (like a spark or heat) to get the reaction started by breaking the initial bonds.

7. How are exothermic and endothermic reactions measured in a lab?
They are measured by observing the change in temperature of the surroundings (usually the solution in a beaker or test tube).
* If the temperature goes up, it is exothermic.
* If the temperature goes down, it is endothermic.

8. Describe the energy diagrams below:
* Left Diagram (Exothermic): This shows an exothermic reaction. The reactants start at a higher energy level, and the products end at a lower energy level. This indicates that energy was released during the reaction.
* Right Diagram (Endothermic): This shows an endothermic reaction. The reactants start at a lower energy level, and the products end at a higher energy level. This indicates that energy was absorbed during the reaction.

9. What observation best represents an exothermic chemical reaction?
The correct answer is a.

Final Answer:
1a: Heat
1b: Inside/Absorbing
1c: Outside/Releasing
2: Chemical reactions (specifically thermochemical reactions).
3: Exothermic releases energy; Endothermic absorbs energy.
4 & 5: (See descriptions above: Exothermic goes High -> Low; Endothermic goes Low -> High).
6: Activation energy is the energy needed to start the reaction/break bonds.
7: By measuring temperature changes (Thermometer).
8: Left is Exothermic (energy released); Right is Endothermic (energy absorbed).
9: a