Name:______Date:______

5.6 What are endo and exo reactions? ADPHS Instructor Ms. Kasia Room 109

UNIT 5 ENERGY

5.6 What are endothermic and exothermic reactions?

Aim:

Do Now: QUIZ (5 mins)

Review: Heat

1. What much heat is released when 10 g of water are cooled from 20˚C to 10˚C?

2. What much heat is absorbed when 10 g of water are heated from 10˚C to 20˚C?

3. What is the difference between these two problems above?

What are endothermic and exothermic reactions?

ENDOTHERMIC / EXOTHERMIC
FUSION:______
VAPORIZATION:______
SUBLIMATION:______/ FREEZING:______
CONDENSATION:______
DEPOSITION:______

LET’S TRY SOME: Solve and indicate whether the phase change is endothermic or exothermic

1. What is the total number of joules of heat energy are absorbed when 100g of water are heated from 20˚C to 30˚C?

2. The heat of fusion for a substance is 122 joules per gram (j/g). How many joules of heat are needed to melt 7.50 grams of this substance at its melting point?

3. What is the total number of joules released by 65g of water when the temperature of the water is lowered from 40˚C to 25˚C?

Directions: Both of the graphs below are graphs we’ve learned in class that have to do with energy. Answer the following questions based on these graphs. (HINT: Use your notes and outside resources.)

a.  Label each graph using the following terminology:

heat of reactant heat of products activation energy heat of reaction fusion vaporization solid liquid gas

Name:______Date:______

5.6 What are endo and exo reactions? ADPHS Instructor Ms. Kasia Room 109

Name:______Date:______

5.6 What are endo and exo reactions? ADPHS Instructor Ms. Kasia Room 109

b.  What is the name of the graph on the left? Is this graph endothermic or exothermic?

c.  What is the name of the graph on the right? Is this graph exothermic or endothermic?

d.  In terms of what the graphs represent and the information they present, what is the difference in these graphs?

e.  If I wanted to know the energy changes in a chemical reaction, which graph would I use?

Review: Heat of fusion and Heat of vaporization

Directions: Explain the following in a coherent, well-written paragraph

___ 1. Explain why we use the q=Hf and q=Hv

___ 2. How we decide whether to use constant for the heat of fusion of the heat of vaporization

___ 3. Explain why we can’t use Table B for any other substance besides water.

___ 4. Explain why temperature does not change during a phase change but heat is required for the phase change.

(Write on a separate sheet of paper and submit by the end of classs.)