1. Chapter Five Gases

2. Chapter Five / Gases Substances That Exist as Gases Element in blue are Gases Noble gases are monatomic All other gases (H 2, N 2, O 2, F 2, Cl 2 ) diatomic molecules.

3. Chapter Five / Gases Substances That Exist as Gases

4. Chapter Five / Gases Substances That Exist as Gases Physical characteristics of Gases : Gases assume the volume and shape of their containers. Gases are the most compressible of the states of matter. Gases will mix evenly and completely when confined to the same container. Gases have much lower densities than liquids and solids.

5. Chapter Five / Gases Gas pressure Gas particles are in constant moving thus they collide with object in their bath. The gases push against the walls of their containers with a force. These collisions produce what we called Gas pressure.

6. Chapter Five / Gases Gas pressure Pressure can be defined as : SI unite of pressure is pascal (Pa) 1 pascal = 1N/m 2. where N=newton, m=meter Atmospheric pressure is the pressure exerted by Earth’s atmosphere. We can measure the atmospheric pressure by barometer. Standard atmospheric pressure (1atm) is the equal to the pressure that supports a column of a mercury exactly 760 mm (or 76cm) high at 0 °C at sea level. 1 atm equal a pressure of 760mmHg.

7. Chapter Five / Gases Gas pressure Unites of pressure : Pascal (Pa), atm, mmHg, torr 1 torr = 1mmHg 1 atm = 760 mmHg 1 atm = 1.01325 x 10 5 Pa. Example1 : convert the pressure of 688 mmHg to atmospheric pressure? 1 atm = 760mmHg ? atm = 688 mmHg 760 X ? = 1 X 688 Pressure = 688 / 760 = 0.905 atm. X

8. Chapter Five / Gases Gas pressure Gas pressure is less than atmospheric pressure Gas pressure is grater than atmospheric pressure Monometer

9. Chapter Five / Gases Gas Laws First we should know that for every gas there is : P (pressure ), T (Temperature) V (volume ), n (mole number). Boyles’s law study the relationship between the pressure and volume of gas. Boyel’s law stated that the pressure of a fixed amount of gas at a constant temperature in inversely proportional to the volume of the gas. The Pressure – Volume Relationships Boyle’s Law

10. Chapter Five / Gases Gas Laws- Boyle’s Law

11. Chapter Five / Gases Gas Laws- Boyle’s Law P 1 V 1 = P 2 V 2 Boyle’s Law

12. Chapter Five / Gases Gas Laws- Boyle’s Law Example 1 : A sample of chlorine gas occupies a volume of 946 mL at a pressure of 726 mmHg. What is the pressure of the gas (in mmHg) if the volume is reduced at constant temperature to 154 mL? P 1 = 726 mmHg, V 1 = 946 ml, P 2 = ?, V 2 = 154 mL. P 1 V 1 = P 2 V 2 726 x 946 = P 2 x 154