31. The mass number of a nucleus is : a) always less than its atomic number: b) the sum of the number of protons and neutrons present in
the nucleus; c) always more than the atomic weight; d) a fraction.

Hot air balloons float in the air because of the difference in density between cold and hot air. in this problem, you will estimate the minimum temperature the gas inside the balloon needs to be, for it to take off. to do this, use the following variables and make these assumptions: the combined weight of the pilot basket together with that of the balloon fabric and other equipment is w. the volume of the hot air inside the balloon when it is inflated is v. the absolute temperature of the hot air at the bottom of the balloon is th (where th> tc). the absolute temperature of the cold air outside the balloon is tc and its density is ďc. the balloon is open at the bottom, so that the pressure inside and outside the balloon is the same. as always, treat air as an ideal gas. use g for the magnitude of the acceleration due to gravity.

Sugar is dissolved in water. which is the solute? sugar neither both water

What determines the average kinetic energy of the particles in a gas? a. the number of collisions b. the number of particles c. the size of the particles d. the temperature