How crowded is the asteroid belt? do spacecraft have trouble traveling through it? answer?

If gases like carbon dioxide and methane make up less than 1% of the total atmosphere, why is it important for scientists to monitor changes in percentages of these gases?

Water is siphoned from a large tank and discharges into the atmosphere through a 50-mm diameter tube. the end of the tube is b = 2.1 m below the tank bottom which is a = 7.4 m deep, and viscous effects are negligible. determine the maximum height h over which the water can be siphoned without cavitation occurring. atmospheric pressure is 101.4 kpa, and the water vapor pressure is 1.79 kpa (absolute)

Atank is filled with an ideal gas at 400 k and pressure of 1.00 atm . part a the tank is heated until the pressure of the gas in the tank doubles. what is the temperature of the gas?