CM8001

a. Exothermic – heat is released from the burning of the charcoal briquette.

b. Endothermic – energy is absorbed by water molecules to form water vapour.

c. Endothermic – energy is absorbed by ice to break the bonds between water molecules to change its state from solid to liquid.

For exothermic reactions, the energy for bond forming must be greater than the energy for bond breaking. Therefore the reactants have a smaller bond strength so it absorbs less heat and the products have a larger bond strength so it produces more heat.

Heat is a type of energy and heat travels from warmer to colder regions. Temperature is a measure of heat energy. Like a cup of hot coffee which transfers heat to its cooler surroundings resulting in a drop of temperature.

a. Octane rating of 98 means a knocking characteristic of 98% isooctane and 2% heptane.

b. The octane rating does not tell us whether the fuel contain oxygenates.