What is the law of definite proportions?

Water (2510 g ) is heated until it just begins to boil. if the water absorbs 5.09×105 j of heat in the process, what was the initial temperature of the water?

If i can still dissolve more sugar into the solution at a certain temperature what would i call that solution

Which of the following would have less momentum than a 52 kg cheetah running at 10 m/s?