Chapter 9.5, Problem 1QQ

Interpretation Introduction

Interpretation:

From the given options, the characteristics of heat energy production has to be chosen.

Concept Introduction:

Heat Energy:

Heat is the transfer or flow due to the difference in temperature between two objects or it is the transfer of energy from one system to another system.  Heat energy arises due to the movements of ions, molecules in solids, liquids and gases.

Exothermic and Endothermic Chemical Reactions:

The chemical reaction in which heat energy is released known as exothermic reaction.  The chemical reaction in which heat energy is absorbed known as endothermic reaction.  The chemical bond will determine whether the reaction is exothermic or endothermic.  If the energy released by bond formation is greater than the energy required to break the bond, then the reaction is said to exothermic and if the energy required to break the bond is greater than the energy released, then it is said to be endothermic reaction. 

Examples for exothermic reaction:

• Making ice cubes.
• Formation of snow in clouds.
• Condensation of rain from water vapour.
• Rusting iron.
• Burning sugar.

Examples for endothermic reactions:

• Melting ice cubes.
• Evaporation of water.
• Producing sugar from photosynthesis.