4 b) energetics

Question 1

4.10 understand that chemical reactions in which heat energy is given out are described as exothermic and those in which heat energy is taken in are endothermic

Answer 1

A reaction that gives out heat is said to be exothermic.

A reaction that absorbs energy is said to be endothermic.

Question 2

4.11 describe simple calorimetry experiments for reactions such as combustion, displacement, dissolving and neutralisation in which heat energy changes can be calculated from measured temperature changes

Answer 2

http://www.shawonnotes.com/index/section_4_physical_chemistry_igcse_chemistry/0-35

Question 3

4.13 understand the use of ΔH to represent enthalpy change for exothermic and endothermic reaction

Answer 3

ΔH is the symbol that represents the amount of energy lost or gained in a reaction.

+ΔH is endothermic (because it gains heat)
- Δ H is exothermic (because it looses heat)

Question 4

4.14 represent exothermic and endothermic reactions on a simple energy level diagram

Answer 4

http://shawonnotes.ucoz.com/IGCSE_Chemistry/images/clip_image101.jpg

Endothermic reaction Exothermic reaction

Question 5

4.15 understand that the breaking of bonds is endothermic and that the making of bonds is exothermic

Answer 5

During chemical reactions, bonds in the reactants have to be broken, and new ones formed to make the products. Breaking bonds needs energy and energy is released when new bonds are made.