What is the differece between a polar molecule and a nonpolar molecule

Needthe meter is the standard unit for: 1) height 2) length 3) weight 4) mass

How could a student test the effect of removing heat from a gas that is stored in a sealed container? what must occur in order for matter to change states?

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