Endothermic and exothermic reactions

Question 1

Chemical reactions always involve

Answer 1

energy changes.

Question 2

Making bonds and breaking bonds involve

Answer 2

energy changes

Question 3

Activation Energy

Answer 3

The energy required to break the bonds in the reactants for a chemical reaction to occur.

Question 4

Endothermic and Exothermic reactions
steps

Answer 4

Step 1: Energy must be SUPPLIED to break chemical bonds of reactants:

Step 2: Energy is RELEASED when new chemical bonds are made in the products

Question 5

A reaction is___if more energy is RELEASED than SUPPLIED. If more energy is SUPPLIED than is RELEASED then the reaction is___

Answer 5

1.Exothermic
2.Endothermic

Question 6

Based on the type of energy (heat) change involved, chemical reactions are classified as either____ or ____

Answer 6

1.Exothermic
2.Endothermic

Question 7

Exothermic

Answer 7

Energy is released

Question 8

Exo-

Answer 8

exit

Question 9

Example

Answer 9

Burning of gasoline

Question 10

Endothermic-

Answer 10

Energy is absorbed

Question 11

Endo

Answer 11

Into

Question 12

Example

Answer 12

Cooking a pancake

Question 13

Endothermic

Answer 13

Heat (energy) taken in
Temperature of the substance drops
Products feel COLD

Question 14

How is an endothermic reaction written

Answer 14

REACTANTS + ENERGY = PRODUCTS
REACTANTS + HEAT = PRODUCTS

Question 15

Exothermic

Answer 15

Heat (energy) given off
Temperature of the substance rises
Products feel HOT

Question 16

You may see an exothermic reaction written like this…

Answer 16

REACTANTS = PRODUCTS + ENERGY
REACTANTS = PRODUCTS + HEAT

Question 17

Examples

Answer 17

Examples

Question 18

Exothermic

Answer 18

Combustion of fuels
Yeast & Hydrogen Peroxide
Epsom salts & water
Condensation of water

Question 19

Endothermic

Answer 19

Photosynthesis
Acidic Acid & Sodium Bicarbonate
cooking egg
melting ice

Question 20

Key Points about Enzymes (special protein)

Answer 20

-Found bonded to reactants
-Act as a CATALYST which speeds up reactions in body

Question 21

Catabolic vs Anabolic Reactions

Answer 21

4 Anabolic BUILDS bonds, example - protein synthesis, building muscle through weight lifting

#5 Catabolic BREAKS bonds, example - digestion

Question 22

How to measure HEAT Change (ΔH)

Answer 22

positive( + ) ΔH signifying an endothermic reaction

negative ( - ) ΔH signifying an exothermic reaction

Question 23

ΔHºf C2H2 = +227 kJ/mole

Answer 23

ENDOTHERMIC!

Question 24

ΔHºf CO2 = -393.5 kJ/mole

Answer 24

EXOTHERMIC!