A helium-filled spherical balloon (whose mass, when empty, is 300 g) has a 0.90 m radius at liftoff where air pressure is 1.0 atm and the temperature is 25 degrees C. When balloon expands, the helium temperature is 210 K, and pressure drops to 0.019 atm. What is the weight of a load that needs to be attached to the balloon to keep it at the verge of lifting? (air density is 1.225 kg/m3, and helium density is 0.179 kg/m3)

hi there!

your question asks at which segment does freezing occur.

since we're talking about water, the freezing point of water will be 32 degrees fahrenheit or below.

hope this ! ~

d) physical means can be used to separate the components of air.

the answer is false. this is because for ice to melt, it requires latent heat of melting. latent heat means heat energy required to change phase without any increase in temperatures. therefore, the ice will take energy from the environment to melt hence atmospheric temperatures will reduce.