A.
Physical change
Step by step explanation;:)
the big number describes the number ratio in a chemical equation
so for example,
2H2 + O2 --> 2H2O means
2 moles of hydrogen reacts with one mole of oxygen to form 2 moles of water
and as you know, the small (subscript) number determines the number of atoms of that element in one molecule of a compound
so I believe that drawing a normal lewis structure ( O=O ) should be correct
The substance has a higher density than water
<u>Answer:</u> The chemical reaction for the synthesis reaction is given below.
<u>Explanation:</u>
Synthesis reaction is defined as a chemical reaction in which two small chemical substances combine together to form a single compound. The general equation for this chemical reaction follows:

For the reaction of calcium and oxygen combining together to form calcium oxide, the equation follows:

By Stoichiometry,
2 moles of calcium element combines together with 1 mole of oxygen gas to produce 2 moles of calcium oxide.
Hence, the chemical equation for the reaction is given above.