CM8001

Process (a) is exothermic because it gives off net heat to the environment as it burns.
Process (B0 is endothermic because water absorbs heat from the skin to overcome its intermolecular bonds which are van der waals forces and hydrogen bondings between the molecules in order to get evaporated into gas molecules.
Process (c) is endothermic because ice absorbs heat from the environment to melt into liquid state.

The bond strength in the product should be significantly greater than that in reactant. This is because for exothermic reaction to occur, the delta enthalpy = |energy of reactant| – |energy of product| < 0. It has been already known that energy is released when bonds are formed to form the product while energy is required to break the bond in the reactant side.

Temperature is a measure of average of the motion of the molecules while heat is the consequence of motion at molecular level.

Set an experiment with 1 hot and 1 cold cup of water separated away from other. Place one hand on the hot cup until no heat can be felt. Then, place the same hand on the cold cup to feel the “coldness”. This feeling of “coldness” is due to the flow of heat from the hot hand to the cold cup of water.

Knocking characteristics of this gasoline is 98% iso-octane and 2% heptane.

We can’t tell whether the fuel does contain oxygenates because octane rating alone does not indicate whether oxygenates are added in.