What happens to water when it changes to ice?
its density increases.
its density decreases.
its mass increases.
its mass decreases.
its volume increases.
its volume decreases.

Its density decreases.

Its volume increases.

Explanation:

There are two changes that happen:

Its density decreases.

Its volume increases.

When the density is less, this is why ice floats on water. Density is calculate by mass/volume. Now mass is same here as we have not added anything here, this means that volume must have changed. Hence, the volume increases that makes the ice less dense.  

answer: - 3.) the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.

solution: - as per the rules, oxidation number of oxygen in its compounds is -2. the sum of oxidation numbers of all the elements of a molecule or compound is zero.

also, the oxidation number in elemental form is zero.

in no, the oxidation number of o is -2 so the oxidation number of n is +2 so that the sum is zero.

similarly, the oxidation number of c in co is +2 and o is -2.

on product side the oxidation number of n is 0 as it is in the elemental form() .

oxidation number of c in carbon dioxide is +4 as there are two oxygen in it and we know that each oxygen is -2.

so, oxidation number of n is changing from +2 to 0 and the oxidation number of c is changing from +2 to +4.

since nitrogen is reduced and hence no is acting as an oxidizing agent. carbon is oxidized and so co is acting as a reducing agent.

so, the right choice is number 3.)the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.

2b2t

explanation:

2b2t