Answer: 1. C. polar covalent: electrons shared between silicon and sulfur but attracted more to the sulfur
2. B) 
3. B) Fluorine
Explanation:
1. A polar covalent bond is defined as the bond which is formed when there is a difference of electronegativities between the atoms.
Electronegativity difference = electronegativity of sulphur- electronegativity of silicon = 2.5 -1.8 = 0.7
Thus as electronegativity difference is less than 1.7 , the cond is polar covalent and as electronegativity of sulphur is more , the electrons will be more towards sulphur.
2. A molecular compound is usually composed of two or more nonmetal elements. Example:
Ionic compound is formed by the transfer of electrons from metals to non metals. Example:
,
and 
3. For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.
Here K is having an oxidation state of +1 and as the compound formed is KZ, the oxidation state of non metallic element Z should be -1. Thus the element Z is flourine which exists as diatomic gas 
Explanation:
Wind helps to get out molecules of water from clothes.
In summer Ball is hard b because due to heat kinetic energy of molecules increases
0.000001ppm
Explanation:
Mass of fluoride = 500g
Volume of water = 500000liters
Unknown:
Parts per million of fluoride = ?
Solution:
The parts per million is the amount of solute in milligram dissolved in a liter of water or milligram per kilogram of solvent
It is a unit used to express very small concentration.
we need to convert g - mg
500g = 500 x 10⁻³mg = 0.5mg
Concentration in parts per million = 
Concentration in parts per million =
= 0.000001ppm
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Answer:
Yes.
Explanation:
Because distillation separates substances based on their different boiling points.