Answer:
The bonds between the molecules of the plastic bottle become weaker as the altitude decreases.
High melting point: due to delocalized electrons
ductile: because of delocalized elections, the lattice of the metal is still held tightly even after undergoing deformation
conductivity: delocalized electrons are free to roam around the metal. So an electric potential (voltage) will create a current flow through the metal
When 1 mole of sodium chloride is mixed with 4 mole of magnesium chloride, the number of chloride ion present will be 5.4198 x
molecules
<h3>Number of molecules in substances</h3>
1 mole of sodium chloride contains 1 mole of chloride ion according to the following equation:
NaCl --->
+ 
4 moles of magnesium chloride will contain moles of chloride ions according to the following equation:

The total number of moles of chloride ions in solution:
1+8 = 9 moles.
1 mole of a substance = 6.022 x 
Thus, the total number of chloride ions present in the mixture = 9 x 6.022 x 
= 5.4198 x
molecules
More on number of molecules in substances can be found here: brainly.com/question/11907018
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Copper oxide(solid) + Sulphuric Acid (aqueous)-> Copper Sulphate (aqueous)+ Water(liquid)
In equation form:
CuO +H2SO4 -> CuSO4 + H2O
The colour change you will see is black to blue as Copper oxide is usually found as a black powder. Upon the reaction with sulphuric acid it will change to a cyan blue.
If you heat the made solution of copper sulphate, the water will evaporate and you will be left with white anhydrous copper sulphate crystals.