5.1

Question 1

Energy

Answer 1

a measure of the ability to do work

Question 2

Examples of energy

Answer 2

heat, light, sound, electricity and chemical energy

Question 3

What increases the average kinetic energy?

Answer 3

heat

Question 4

What is a system?

Answer 4

an area of interest

Question 5

What is an open system?

Answer 5

can exchange energy and matter with surroundings

Question 6

What is an closed system?

Answer 6

can exchange energy but not matter with the surroundings

Question 7

What is a surrounding?

Answer 7

in theory, everything in the universe outside the system

Question 8

Enthalpy (H)

Answer 8

a measure of the amount of heat energy contained

Question 9

Where is enthalpy stored?

Answer 9

in the chemical bonds and intermolecular forces as potential energy

Question 10

What happens if heat is added to a system?

Answer 10

the enthalpy increases and therefore the ∆H is positive

Question 11

What happens if heat is released from the system?

Answer 11

the enthalpy of the system decreases and ∆H is negative

Question 12

Exothermic reaction

Answer 12

result in a transfer of enthalpy from the system to the surroundings

• The reactants have more enthalpy than the products
• ∆H is negative
• Most combustion and neutralization reactions are exothermic

Question 13

Endothermic reaction

Answer 13

result in a transfer of enthalpy from the surroundings to the system

• The products have more enthalpy than the reactants
• ∆H is positive

Question 14

Standard conditions for enthalpy changes

Answer 14

• A pressure of 100 kPa
• Concentrations of 1 mol dm-3 for all solutions
• All the substances in their standard states

Question 15

What does kinetic energy and movement depends on?

Answer 15

the temperature, if the temperature is decreased – the kinetic energy is decreased.

Question 16

Absolute zero

Answer 16

(-273 ℃) – the lowest possible temperature attainable, the temperature at which all movement stops.

Question 17

What does the increase in temperature when an object is heated depend on?

Answer 17

• The mass of the object
• The heat added
• The nature of the substance

Question 18

What is the specific heat capacity of water?

Answer 18

4.18

Question 19

Standard enthalpy change of combustion

Answer 19

standard enthalpy change of combustion (∆H⊖c) is the enthalpy change for the complete combustion of one mole of a substance in its standard state in excess oxygen under standard conditions.