Ccl2f2 is considered to be environmentally safe and is used as a refrigerant. the heat of vaporization of ccl2f2 is 289 j/g. what mass of this substance must evaporate in order to freeze 2 moles of water initially at 20°c? the heat of fusion of water is 334 j/g and the specific heat of water is 4.18 j/g-k.

Which term best describes the phrase “something that happens”?

Astudent is performing an experiment comparing sound and light waves. the student gathers the following data. what conclusion does the student most likely make based on this data? light waves always travel the same speed; however, the speed of sound is determined by the medium that it travels through. all sound waves always have the same energy, so the temperature of the medium does not affect wave speed. light needs to vibrate particles, so it travels fastest in tightly packed solids, while sound does not need a medium, so it travels fastest in a gas. tightly packed particles in solids slow down the light waves; however, sound waves make particles bounce into each other, so they travel faster in solids.

Karen is running forward at a speed of 9 m/s. she tosses her sweaty headband backward at a speed of 20 m/s. the speed of the headband, to the nearest whole number relative to a stationary observer watching karen