Form one how is the long-term effect of adding salt to ice is costly to Motorists​

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.