Answer: Option (D) is the correct answer.
Explanation:
The chemical reaction equation will be as follows.

This means a new substance has been formed and a chemical change has taken place.
A chemical reaction in which heat energy is absorbed by the reactant molecules is known as an endothermic reaction.
For example,
On the other hand, a chemical reaction in which heat energy is released by the reactant molecules is known as an exothermic reaction.
For example,
is an exothermic reaction.
Thus, we can conclude that in the given situation the beaker most likely felt warm because a chemical reaction was producing a new substance.

where
the Avogadro's constant that relates the number of particles to their number, in the unit moles
.
The molar mass of propanol- mass per mole propanol- can be directly deduced from its molecular formula with reference to a modern periodic table.

of propanol molecules would thus have a mass of 
If it is incomplete or complete combustion. Normally the problems question with tell you.
EX:
"In the presence of plenty of oxygen" is complete combustion
"Not enough oxygen present" is incomplete combustion
Answer:
One of the errors for low percentage of magnesium could be because not all the magnesium may have reacted.
Explanation:
During the heating process, if the magnesium have not reacted completely, it can lead to low percentage of magnesium in the oxide formed. The product may still look a bit greyish rather than whitish after the heating process.
Answer:Decomposers break down waste and dead organisms.
Explanation:
Decomposers help keep the environment clean by acting on waste