It should be A
But you have this as chemistry? I think this is like a biology question
I think the correct answer would be the first option. As the hiker reaches the top of the mountain, the plastic bag would, most likely, expand. Before starting, the plastic bag would have a certain amount of gas particles inside. As the you hike, the pressure would decrease causing for the gas molecules to reestablish equilibrium thus pushing the bag outwards. In other words, expanding the bag. Also, base from the ideal gas equation, PV = nRT, at constant temperature and number of moles, pressure and volume are inversely related. Thus, as the pressure decreases, the volume of the system would increase accordingly.
Answer: The phase change for A and B respectively is condensation, freezing.
Explanation:
A process in which gaseous state of a substance converts into liquid state is called condensation.
For example, conversion of steam into water.
A process in which liquid state of a substance converts into solid state is called freezing.
For example, conversion of liquid water into ice.
Thus, we can conclude that the phase change for A and B respectively is condensation and freezing.
I believe the answer is B??????????? Hope this helps
~Queensupreme
Answer: The reaction of formation of ions by fluorine and potassium is 
.
Explanation:
Atomic number of potassium is 19 and its electronic distribution is 2, 8, 8, 1. So, in order to attain stability it needs to lose 1 electron due to which it forms 
ion.
Atomic number of fluorine is 9 and its electronic distribution is 2, 7. In order to attain stability it needs to gain one electron and hence forms 
ion.
Therefore, when both these ions come in contact with each other then it leads to the formation of KF compound.
The reaction equation for this is as follows.
Thus, we can conclude that the reaction of formation of ions by fluorine and potassium is .
