Name _______________________________ Date:_____________
Period:____
Honors Review Unit 10: Energy Changes and Reaction Rates
1.
State the law of conservation of energy.
_______________________________________________________________________
T or F When a chemical system releases energy, the surroundings must absorb an equal
amount of energy.
2.
When chemical bonds are formed, energy is __________________(absorbed, released)
In order to break chemical bonds, energy is ___________________(absorbed, released).
3.
If you are holding a beaker in which an exothermic reaction is occurring, the beaker would
feel________________ (warmer, cooler) to the touch because energy is being ____________
(absorbed, released) into the surroundings.
4.
The potential energy diagram shown is for an ENDOTHERMIC / EXOTHERMIC reaction.
(circle one)
Label the reactants, the products, activation energy (Eact), and change in energy (ΔE) .
potential
energy
reaction progress
Circle the correct statement.
In an exothermic reaction, heat is ______________
( absorbed from / released to ) the
surroundings, and the surroundings ________________ (cool down / warm up).
Touching the beaker with this reaction would feel _____________ (cooler / warmer) and a
thermometer would show the temperature ____________ (lowering / rising) .
T or F
In this diagram, the reactants have more stored energy than the products.
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5.
The potential energy diagram is for an ENDOTHERMIC / EXOTHERMIC reaction. (circle one)
Label the reactants, the products, activation energy (Eact), and change in energy (ΔE) .
potential
energy
reaction progress
Circle the correct statement.
In an endothermic reaction, heat is ___________ ( absorbed from / released to) the
surroundings, and the surroundings ______________ ( cool down / warm up).
Touching the beaker with this reaction would feel ______________ (cooler / warmer) , and a
thermometer would show the temperature ______________ ( lowering / rising).
T or F
In this diagram, the reactants have more stored energy than the products.
6.
Define activation energy: ____________________________________________________________
7.
A catalyst is a substance that _________________(increases, decreases) the reaction rate.
It works by _________________(raising, lowering) the activation energy for the reaction.
8.
T or F Catalysts will be changed in the reaction and can never be reused.
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reaction progress
9.
Consider reactions B and C above.
The different heights of reactions B and C represent the _________________________ of the reaction.
Reaction ___ is a catalyzed reaction, while Reaction ___ is an uncatalyzed reaction.
Reaction B has a _____________ ( lower / higher) activation energy and occurs at a _________
(slower / faster) rate.
10.
Circle EACH of the following that could express a reaction rate in amount per time:
mol/L
g/s
s/mol
mol/min
g/mol
11. T or F Collision theory states that the ONLY requirement needed for a chemical reaction to occur
is that the reactant particles must collide.
12. T or F To be effective, a collision requires both the proper orientation of particles and the
collisions must occur with sufficient energy to react.
13. How does each factor affect the rate of a reaction?
1) increased concentration
effect on rate: increases or decreases
2) increased temperature
effect on rate: increases or decreases
3) increased activation energy
effect on rate: increases or decreases
4) use of a catalyst
effect on rate: increases or decreases
5) increased surface area
effect on rate: increases or decreases
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14. Explain why increasing the concentration of reactants increases the reaction rate.
Higher concentrations cause more ________________________ between _____________________.
15. Explain why a reaction rate increases with an increase in temperature.
Higher temperatures cause more _______________________ of greater ______________________.
16. Reaction rates increase with ___________ (smaller / larger) particle sizes which provide ________
(less / more) surface area of reactant available for collisions.
17. A catalyst is a substance that _________________(speeds up, slows down) the reaction rate.
It works by _________________(raising, lowering ) the activation energy.
Catalysts _________ (do, do not) get consumed in the reaction and can be used over again.
reaction progress
18. Consider reactions B and C above.
Which reaction has a higher activation energy? _________________
Which reaction will be faster? ______________________
19. Why is it easier to light a pile of sawdust on fire compared to a large log?
_____________________________________________________________________________
20. Consider a candle on a table that burns for 2 hours before going out.
Would you classify this system as OPEN, CLOSED, or ISOLATED? Explain.
__________________ because
_____________________________________________________________________________
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