CM8001

a. Exothermic. Heat is given out when coal briquette is burnt and used by people for heating up stuff, cooking food, used to power trains (heat to kinetic energy by heating moving wind that drives some turbine..) and also to keep people warm during cold weather.
b. Endothermic with respect to water molecules. It absorbs heat energy from our skin, hence we feel a cooling sensation
c. Endothermic. Solid to liquid transition involves absorbing energy to achieve a higher energy state of product (liquid state water).

For a good explosion, energy needs to be given out for it to be exothermic. Thus product’s energy needs to be lower than that of the reactants. Enthalpy change is determined by the equation delta H = bonds broken (energy taken in) – bonds formation (energy given out). Thus the magnitude of bond formation is bigger than the magnitude of bond breaking. Hence we can conclude that the product bond strength is bigger than that of the reactant bond strength.

Coffee – as the coffee is chilled, heat is lost, hence temperature also drops.
Heat – total energy of molecular motion, a process.
Temperature – measure of average heat/thermal energy of the molecules in a substance, known magnitude.
Another analogy would be temperature being the current score on the scoreboard of a soccer game, the heat being the goals scored. Temperature is like a measurement of heat just like how the scoreboard measures the amount of goals.
My friends are quite smart and all know Chemistry.

a. It is slightly higher than octane – 98% of isooctane and 2% of heptane. Hence slightly abit more prone to knocking.
b. It does not tell us anything about the availability of oxygenates. It may or may not contain. Even the word premium does not do anything to save it. The only is through determination of molecular compound composition through fractional distillation.