Directions: Select the choice that best fits each statement. The following questions(s) refer to a pond in southern Canada. In 1950 the pH of the pond water was 8.2, but by 2000 the pH had decreased to 5.2. Which of the following changes would also be expected in the pond over the same time period? Increased levels of dissolved oxygen Increased levels of heavy metals Increased number of fish species

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.

Some animals that try to adapt to climate changes eventually die due to starvation, as climate change alters the web.

Which states of matter have particles that move independently of one another with very little attraction?