Energetics

Question 1

Exothermic definition (condensing)

Answer 1

When energy is given out (heat, light, sound, electrical energy) E.G. complete combustion of hydrocarbons (methane)

Question 2

Endothermic definition (boiling, melting, evaporation, sublimation)

Answer 2

When energy is taken in, observed by a drop in temperature of the surroundings E.G. potassium chloride and water

Question 3

Calorimetry for liquid chemical reactions

Answer 3

• used to measure the amount of energy released/taken in, in chemical reactions
  Use a thermometer and a polystyrene cup
  • used to measure temperature changes
  • for combustion, displacement, dissolving, neutralisation

Question 4

Energy transfer equation

Answer 4

Q =mc /_\ T

m = mass of water
c = 4.18
Delta T = temperature change

Question 5

Enthalpy change equation

Answer 5

/_\H = Q/n

/_\H = enthalpy change
Q = heat energy (convert to KJ)
n = number of moles

Question 6

Must have signs for exothermic and endothermic

Answer 6

(+) is exo

(-) is endo

Question 7

What are the steps to work out enthalpy change

Answer 7

Work out energy transfer, then moles, then enthalpy change

Question 8

Calorimetry for fuel

Answer 8

• for measuring energy released from fields
  Use a copper can then thermometer and spirit burner
  • weight burner before and after to see how much fuel has been burned
  • add 100 ml of water to copper can, which is clamped above spirit burner
  • Record temperature of water before and after
  • allowed to burn for five minutes

Question 9

Energy profile diagrams: Exothermic

Answer 9

• when a New chemical bond forms energy is released

Goes from high to low

Question 10

Energy profile diagrams: endothermic

Answer 10

• to break a chemical bond energy must be put into the bond

Goes from low to high

Question 11

What is MexoBendo

Answer 11

M stands for making bonds

B stands for breaking bonds