´identify the independent, dependent, and controlled variables in your experiment which is how does adding salt affect the freezing point of water?

An independent variable is a variable that is not affected in the experiment. It is what experimenter controls. Here, the concentration of salt is the independent variable.
On the other side, a dependent variable is called dependent because it depends on the independent variables. It is what is affected and observed during the experiment. Here, the freezing point of water is affected and, thus, it is the dependent variable.
A controlled variable is a variable that must remain unchanged (must be constant) during the experiment so that the effect on the dependent variable depends only on the independent variable. Here, the volume of water must be constant, so it is the controlled variable.

The phase where ice changes directly to gas is called sublimation 

Answer(d) unstable compounds that convert to acetals in the presence of alcohol and an acid; (b) semiacetals produced by alcohol subtraction from ketone;