Giving 15 points how do you calculate the density of an object?

Astudent is working in the lab to determine how time affect impulse the student keeps the force the same in each row but changes impact the time some data is shown witch trial has the greatest a student is working in the lab to determine how time affect impulse the student keeps the fours the same in each row but change is the impact time some data shown witch trial has the greatest impulse

How much energy must a refrigerator absorb from 225 g of water so that the temperature of the water will drop from 35°c to 5°c

In a hydrogen molecule there are a total of four charges, 2 protons in the two nuclei, and 2 electrons. how many unique charge-pairs are there (without double counting)?