5.1 Measuring Energy Changes

Question 1

What is energy?

Answer 1

A measurement for the ability to do work

Question 2

Distinguish between heat and temperature

Answer 2

• Heat is a measure of the total energy ina given amount of substance and therefore depends on the amount of substance.
• Temperature is a measure of “hotness” of a substance. Represents average kinetic energy but is independent of the amount of substance.

Question 3

What is a system?

Answer 3

A system is the part of the universe that was chosen for study

Question 4

What are surroundings?

Answer 4

Everything else in the universe aside from the system

Question 5

What are the different types of systems?

Answer 5

• Open system
• Closed system

Question 6

What is an open system?

Answer 6

An open system is a system that can exchange energy and matter with the surroundings

Question 7

What is a closed system?

Answer 7

A closed system is a system that can exchange energy but not matter with the environment

Question 8

What is enthalpy?

Answer 8

Enthalpy is the heat content of a system

Question 9

What is an exothermic reaction?

Answer 9

• A reaction where the bonds formed are stronger than the bonds broken.
• Energy is released and temperature increases.
• ΔH < 0

Question 10

What is an endothermic reaction?

Answer 10

• A reaction where the bonds broken are stronger than the bonds formed
• Energy is absorbed, temperature decreases
• ΔH > 0

Question 11

How to calculate enthalpy change?

Answer 11

ΔH=Enthalpy of products - enthalpy of reactants

Question 12

How can enthalpy change be measured experimentally?

Answer 12

Via calorimetry

Question 13

Formula for calculating enthalpy change experimentally

Answer 13

Heat energy = (cmΔT)/1000
c - specific heat capacity, 4.18 for water
m - mass of the water in grams
ΔT - temperature change of water
ΔH = Heat energy/n (amount of other substance)