[سحر البيان]

9. Which one of the following statements is ture concerning the atmospheric pressure in a mine that is 500 m below sea level?
A) greater than 1 atm
B) less than 1 atm
C) equal to 1 atm
D) approaching 0 atm

شرحته قبل ... شوفوه هنا جا على هيئة اختياري

10. What is the difference between a gas and a vapor?
A) A gas is a substance normally in the gaseous state at normal atmospheric conditions (25C, 1 atm); a vapor is the gaseous form of any substance that is a liquid or a solid at normal temperatures and pressures.
B) A gas is the gaseous form of any substance; a vapor refers to a gas over a water surface.
C) A gas is a substance normally in the gaseous state at normal atmospheric conditions (25C, 1 atm); a vapor is a gas over a water surface.
D) A gas and a vapor are two interchangeable nomenclatures; they are idenctical.

سؤال جميل ماهو الفرق بين الغاز و البخار ....
هناك موجوده بطبيعة على هيئة غاز مثل الأكسجين .... و لكن البخار هي مواد ممكن تكون على هيئة سائل و بالحراره تتحول الى غاز مثل الماء ...

11. At 25ºC, which of the following substances in the gas phase should be properly called a gas and which should be called a vapor: molecular nitrogen (N2), mercury (Hg)?
A) N2 is a gas; Hg is a gas
B) N2 is a vapor; Hg is a vapor
C) N2 is a gas; Hg is a vapor
D) N2 is a vapor; Hg is a gas.

[align=left]17. Explain why a helium weather balloon expands as it rises in the air. Assume that the temperature remains constant.
A) The number of moles of gas increase as the balloon rises.
B) The atmosperic pressure outside the balloon increases, and the gas inside expands to equal that pressure.
C) Pressure and volume are directly proportional at constant temperature.
D) The atmosperic pressure outside the balloon

decreases, and the gas inside expands to equal that pressure.[/align

البالون يكون معباء بالغاز ... و عندما يرتفع يقل الضغظ المحيط به ... مما ينشاء عنه أن حجم الغاز يزيد ( قانون بويل)