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Changes in Matter & Energy Section 5.1

PRACTICE (Page 300)
1. (a) chemical (new products: water and carbon dioxide)
(b) physical (no new products)
(c) chemical (new products: water and carbon dioxide)
(d) physical (no new products)
(e) chemical (new products: hydrogen gas and zinc chloride)
(f) physical (no new products)

3. All of these systems may be regarded as open because energy and/or matter may escape from the system, often in the form of gases. However, (a) may be considered a closed system for the instant at which the air–fuel mixture ignites.

4. The thimbleful has greater average thermal energy per molecule, but the pool has greater total thermal energy.

5. (a) exothermic
(b) exothermic
(c) endothermic
System Surroundings
(a) gas and oxygen air and metal parts
(b) ice hand
(c) gas and oxygen air and metal parts
(d) wax stove
(e) zinc and acid beaker and water solvent
(f) ice body part

PRACTICE (Page 302)
8. Aluminum has the lowest specific heat capacity, which implies that it requires the least amount of heat to change temperature, and will undergo the greatest temperature change.

1. Changes of state from solid to liquid, liquid to gas, and solid to gas are endothermic; changes of state from gas to liquid, liquid to solid, and gas to solid are exothermic.

2. mass, temperature change, specific heat capacity

3. (a) chemical (new products; rearrangement of atoms to new molecules)
(b) physical (no new product; same molecules)
(c) nuclear (uranium decays to form new atoms)

Molar Enthalpies Section 5.2

PRACTICE (Page 311)
6. No heat is transferred to the outside environment; negligible heat is transferred to calorimeter materials; dilute aqueous solutions have the same specific heat capacity as water.

7. (a) ΔHvaporization
(b) ΔHsublimation
(c) ΔHsolution
(d) ΔHcombustion
(e) ΔHneutralization

For Questions page 312