Chemical change is any change that results in the formation of new chemical substances. At the molecular level, chemical change involves making or breaking of bonds between atoms. These changes are chemical: iron rusting (iron oxide forms) gasoline burning (water vapor and carbon dioxide form)
There are several possibilities. Here are a few that occur to me:
-- If Point-A is the summit of Pike's Peak, he may feel somewhat
short of breath.
-- If Point-A is his grandmother's house, he may feel a great sense
of pleasant anticipation.
-- If Point-A is his office on Monday morning, then he may feel
a tightening sensation in his chest.;
-- If Point-A is his home on Friday afternoon, then he feels the
effects of a slow and steady drop in his blood pressure.
I finer point might be put to it if we had any idea of where
Point-A is, and what it represents in the grand scheme
of things.
3 is the answer to your question
Answer:
The steps are outlined in the explanation below.
Explanation:
The average velocity is derived midpoint from the initial to the final velocity. Here is the proof:
Find the total displacement:
let the displacement be given by the letter s
Then since the average velocity is defined as: 
where t = final time
t₀ = initial time
v = final speed
v₀ = initial time
where x denotes the position, then

where v =
and dx = change in distance with respect to time.
6.022*10^23 atoms/mole of reactant
(this is chemistry not physics)