Momentum is a property of an object, but it is different than a physical or chemical property, such as boiling point or flammability. how is momentum different?

Well, momentum is defined as mass times acceleration. As far as I know it is independent of temperature, pressure, and chemical reaction. If you've got 1kg of anything moving at 1m/s you've got a momentum of 1kg m/s, regardless. Or at least you do in low speed newtonian classical physics.

The electrostatic force between two point charge particles is directly proportional to the product of their charges and inversely proportional to the square of the distance between them. So, if you double the individual charges while keeping the same distance, the net electrostatic force will be four times the previous value.

Explanation:

Since, we know

F = (k×q1×q2)/r²

When the charges are doubled, we have :

F' = (k × 2q1 × 2q2)/r²

F' = 4 (k×q1×q2)/r²

Thus,

F' = 4F

Hence, the force becomes 4 times its initial value.