1. Entropy
Chapter 16-5

2. Entropy and Free Energy
18.4
Entropy and Free Energy
Inside a pile of oily rags or a stack of hay that has not been thoroughly dried, decomposition causes heat to build up. When heat cannot escape, the temperature can become high enough to cause a fire. You will learn about the conditions that will produce a spontaneous chemical reaction.

3. Free Energy and Spontaneous Reactions
18.4
Free Energy and Spontaneous Reactions
A spontaneous reaction is a physical or chemical change that occurs with no outside intervention.
Cadmium sulfide forms spontaneously when solutions of sodium sulfide and cadmium nitrate are mixed. Inferring Is free energy released in this reaction?

4. Free Energy and Spontaneous Reactions
18.4
Free Energy and Spontaneous Reactions
A nonspontaneous reaction is a reaction that does not favor the formation of products at the specified conditions.
Photosynthesis is a nonspontaneous reaction that requires an input of energy.
Many non-spontaneous reactions are required for a plant to grow. Nonspontaneous reactions can occur when they are coupled with spontaneous reactions. Inferring What is another requirement for this photosynthesis reaction?

5. Free Energy and Spontaneous Reactions
18.4
Free Energy and Spontaneous Reactions
Spontaneous reactions produce substantial amounts of products at equilibrium and release free energy.
Free energy is energy that is available to do work.

6. Entropy 18.4 Entropy is a measure of the disorder of a system.
Physical and chemical systems attain the lowest possible energy.
The law of disorder states that the natural tendency is for systems to move in the direction of maximum disorder or randomness.
An increase in entropy favors the spontaneous chemical reaction; a decrease favors the nonspontaneous reaction.
The law of disorder states that spontaneous processes always proceed in such a way that entropy of the universe increases. This is the second law of thermodynamics.

7. 18.4
Entropy
For a given substance, the entropy of the gas is greater than the entropy of the liquid or the solid. Similarly, the entropy of the liquid is greater than that of the solid.
Entropy is a measure of the disorder of a system. a) For a given substance, the entropy of the gas is greater than the entropy of the liquid or the solid. Similarly, the entropy of the liquid is greater than that of the solid.Thus entropy increases in reactions in which solid reactants form liquid or gaseous products. Entropy also increases when liquid reactants form gaseous products. b) Entropy increases when a substance is divided into parts. For instance, entropy increases when a crystalline ionic compound, such as sodium chloride, dissolves in water. This is because the solute particles— sodium ions and chloride ions—are more separated in solution than they are in the crystal form. c) Entropy tends to increase in chemical reactions in which the total number of product molecules is greater than the total number of reactant molecules. d) Entropy tends to increase when temperature increases. As the temperature increases, the molecules move faster and faster, which increases the disorder.

8. Entropy 18.4 Entropy increases when a substance is divided into parts.
Entropy is a measure of the disorder of a system. a) For a given substance, the entropy of the gas is greater than the entropy of the liquid or the solid. Similarly, the entropy of the liquid is greater than that of the solid. Thus entropy increases in reactions in which solid reactants form liquid or gaseous products. Entropy also increases when liquid reactants form gaseous products. b) Entropy increases when a substance is divided into parts. For instance, entropy increases when a crystalline ionic compound, such as sodium chloride, dissolves in water. This is because the solute particles— sodium ions and chloride ions—are more separated in solution than they are in the crystal form. c) Entropy tends to increase in chemical reactions in which the total number of product molecules is greater than the total number of reactant molecules. d) Entropy tends to increase when temperature increases. As the temperature increases, the molecules move faster and faster, which increases the disorder.

9. 18.4
Entropy
Entropy tends to increase in chemical reactions in which the total number of product molecules is greater than the total number of reactant molecules.
Entropy is a measure of the disorder of a system. a) For a given substance, the entropy of the gas is greater than the entropy of the liquid or the solid. Similarly, the entropy of the liquid is greater than that of the solid. Thus entropy increases in reactions in which solid reactants form liquid or gaseous products. Entropy also increases when liquid reactants form gaseous products. b) Entropy increases when a substance is divided into parts. For instance, entropy increases when a crystalline ionic compound, such as sodium chloride, dissolves in water. This is because the solute particles— sodium ions and chloride ions—are more separated in solution than they are in the crystal form. c) Entropy tends to increase in chemical reactions in which the total number of product molecules is greater than the total number of reactant molecules. d) Entropy tends to increase when temperature increases. As the temperature increases, the molecules move faster and faster, which increases the disorder.

10. 18.4
Entropy
Entropy tends to increase when temperature increases. As the temperature increases, the molecules move faster and faster, which increases the disorder.
Entropy is a measure of the disorder of a system. a) For a given substance, the entropy of the gas is greater than the entropy of the liquid or the solid. Similarly, the entropy of the liquid is greater than that of the solid. Thus entropy increases in reactions in which solid reactants form liquid or gaseous products. Entropy also increases when liquid reactants form gaseous products. b) Entropy increases when a substance is divided into parts. For instance, entropy increases when a crystalline ionic compound, such as sodium chloride, dissolves in water. This is because the solute particles— sodium ions and chloride ions—are more separated in solution than they are in the crystal form. c) Entropy tends to increase in chemical reactions in which the total number of product molecules is greater than the total number of reactant molecules. d) Entropy tends to increase when temperature increases. As the temperature increases, the molecules move faster and faster, which increases the disorder.

11. Enthalpy, Entropy, and Free Energy
18.4
Enthalpy, Entropy, and Free Energy
The size and direction of enthalpy changes and entropy changes together determine whether a reaction is spontaneous; that is, whether it favors products and releases free energy.

12. Enthalpy, Entropy, and Free Energy
18.4
Enthalpy, Entropy, and Free Energy