PLEASE HELP URGENT 1. at how much energy is required to melt a 30.0-gram sample of water at its melting point?

2. at 1 atmosphere of pressure, 20.0 g of a compound at its normal boiling point are converted to a gas by the addition of 23,000 joules. what is the heat of vaporization for the compound in J/g?

Describe the difference between a. a hypothesis and a theory and b. an observation and an experiment.

A40 kilogram skier starts at the top of a 12 meter high slope. at the bottom, she is travelling 10 meters per second. how much energy does she lose to friction

Astudent pours 10.0 g of salt into a container of water and observes the amount of time it takes for the salt to dissolve. she then repeats the process using the same amounts of salt and water but this time she slowly stirs the mixture while it is dissolving. the student performs the experiment one more time but this time she stirs the mixture rapidly. the dependent variable in this experiment is: time for salt to dissolve speed of stirring amount of water mass of salt