How many variables should a scientist change at one time to have a good experiment?

6. using 3 – 4 sentences explain (in your own words) why water expands when it freezes? 7. using your knowledge of colligative properties explain whether sodium chloride or calcium chloride would be a more effective substance to melt the ice on a slick sidewalk. use 3 – 4 sentences in your explanation.

Which of the following has wavelength longer than the wavelength of viable light? a) x rays b) gamma rays c) radios waves d) ultraviolet waves

Which of the following is not true about the atomic model of substances?