Explanation:
1) 
Energy will be absorbed by the Cs(s) to get converted into Cs(g). In order to break the strong association of particles present in solid to convert it into gaseous state energy will be needed. So, energy will be absorbed by the Cs solid in this reaction.
2) 
Energy will be absorbed by 
gas in order to break bond between two Cl atoms to form isolated(alone) single chlorine atom.So, the energy will be absorbed by the chlorine gas molecule in this reaction.
3) 
Energy will be absorbed by the Cs(g) to get converted into 
cation. In order to remove an electron from the outer most shell of Cs atom energy will be required by Cs atom, So, energy will be absorbed in this reaction.
4) 
Energy will get release in formation of 
anion from Cl atom in gaseous state. Chlorine atom need one electron to attain noble gas configuration. So, when an electron is added to the outer most shell of chlorine it attains stability of fully filled outermost shell by which it releases energy on addition of an electron.
5) 
Energy will get release on formation of CsCl(s) from
cation and anion. since both are oppositely charged ion and due to strong electrostatic interaction will get converted into stable molecule of CsCl (s) with release in an energy.
Physical property- is an aspect of matter that can be observed or measured without touching changing it.
Chemical property- may only be observed by changing the chemical identity of a substance.
The difference would be that for physical property's you dont need to do anything to figure out what they are, but for chemical properties you need to change something to observe them.
True, Petroleum is used to make synthetic plastics and numerous petrochemical.
