12, if the decimal is over five, round up. If it's not, round down. Not sure what you mean by significant figures.
3. Eukarya...is the answer
Answer:
The constant density decreases
Explanation:
As the temperature of a solvent increases, the solubility of any gas dissolved in that solvent decreases.
For example:
when the temperature of a river, lake or stream is raised high , due to discharge of hot water from some industrial process the solubility of the oxygen in the water is decreased .The fish and the other organisms that live in the water bodies such as rivers, ponds, lakes etc can survive only in the presence of oxygen and decrease in the concentration of the water due to increased temperature can lead to the death of the fish and this may in turn damage the ecosystem.
In the above example, water is considered as the solvent and the oxygen is considered as the solute. When the temperature of the solvent that is water increases, the solubility of the gas that is oxygen in the solvent decreases.
Therefore the answer is decreases
When sodium amide i.e.
reacts with water i.e. 
results in the formation of sodium hydroxide i.e. 
and ammonia 
.
The chemical reaction is given by:
Now, when ammonia i.e. reacts with water results in the formation of ammonium hydroxide i.e. 
The chemical reaction is given by:
Thus, the products of the above reactions are ammonia and ammonium hydroxide (without sodium ion).
The structures of the products are shown in figure (1): ammonium hydroxide and figure (2) ammonia.
