J Unit 4. Kinetics+Equilibrium 4.4 What is endothermic and exothermic reactions? March 15, 2011 Do Now: Going over questions from yesterday AIM: How do.

J

Unit 4. Kinetics+Equilibrium4.4 What is endothermic and exothermic

reactions? March 15, 2011

Do Now:

Going over questions from yesterday

AIM: How do we distinguish between endothermic and exothermic reactions?

ENDOTHERMIC REACTIONS

DEFINITION

reactions that take in energy (heat)

heat is absorbed from the surroundings

EXAMPLES

solid liquid (ice cream melting)

liquid gas (boiling water)

solid gas

melting

vaporization

sublimation

Where is the heat?

• 2H2O(g) + heat ↔ 2H2(g) + O2(g)

• 2H2O(g) + 103 kJ ↔ 2H2(g) + O2(g)

• 2POCl3(g) + energy ↔ 2PCl3(g) + O2(g)

Circle where the heat is located. Indicate whether it is a reactant or a product

KEY IDEA

endothermic reaction

sample absorbs heat

heat is on the left side (reactant side)

EXOTHERMIC REACTIONS

DEFINITION

Reactions that release energy (heat)

EXAMPLE

gas liquid (rain)

liquid solid (making ice cubes)

gas solid

condensation

freezing

deposition

Where is the heat?

• 8H2 + S8 8H2S + heat

• 8H2 + S8 8H2S + 1026 J

Circle where the heat is located. Indicate whether it is a reactant or a product

KEY IDEA

exothermic reaction sample releases heat

heat is on the right side (product side)

INDEPENDENT PRACTICE

1. To be collected at the end of CLASS!

2. COME SEE ME AFTER SCHOOL IF YOU NEED TO MAKE UP WORK!