3. in what grade level do students grow the quickest?
independent variable:
dependent variable:
hypothesis:

Independent Variable: Grade Level

Dependent Variable: Growth in height

Hypothesis: Students in [Insert the grade level you believe will grow the quickest here] will experience the quickest growth in height.

Explanation:

Independent variables are the factors in which you manipulate to gain your results, in this case you would be changing the grade level you would observe to see the height.

Dependent variables are the factors that respond to changes in the independent variables. You don't control these events, you simply observe them. In this case, you merely observe the growth in height in accordance to the different grade levels you observe.

For the hypothesis, you would create your own hypothesis based on a guess you have. You create a hypothesis not based on the data, but on what you believe will be correct before doing the experiment. It doesn't have to be the correct answer, but just your thoughts.

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

the temperature of the gas, in k, not celsius.