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DEFINITION OF GASES The state of matter that expands freely to fill their containers and are lower in density than liquids and solids.

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Presentation on theme: "DEFINITION OF GASES The state of matter that expands freely to fill their containers and are lower in density than liquids and solids."— Presentation transcript:

1 DEFINITION OF GASES The state of matter that expands freely to fill their containers and are lower in density than liquids and solids.

2 Kinetic Molecular Gas Theory 1. Gases are considered the simplest state of matter 2. Gases are composed of molecules in random order and move in continuous straight line motion 3. Molecules collide elastically

3 4. Molecules collide with walls of container to exert pressure 5. A zero force of attraction is assumed between molecules 6. Actual gas molecules have no volume compared to the volume of space they are contained in  Please note these define Ideal Gases. Real gases deviate...

4 Real Gases have molecular volume - they take up some space. Real gases also have some attraction for each other. These deviations are especially evident when the gas is under high pressure, low temperature, and decreased velocity (when they are close together!!)

5 Volume refers to the space matter occupies. The volume of 1 mole of solid carbon dioxide is 28 ml, which is not much bigger than a large ice cube. However, the same number of carbon dioxide molecules, as a gas, occupies ml, a volume almost 1000 times greater. Only a small fraction of the total volume of the gas is occupied by the molecules themselves. The rest of the volume is empty space.

6 Thus, there is a lot of room for the molecules to move closer together - by compression. When a gas is compressed, the same number of particles can now occupy a different volume and if that volume is decreased the pressure increases and vice versa. This is so because of when the volume decreases so does the inside surface area so the molecules can now exert more pressure on a concentrated area.

7 Temperature Gas temperature is measured in degrees Kelvin, or Celsius. Realizing that temperature is the measure of the average kinetic energy, imagine some ping-pong balls confined to a box. When the ping-pong balls have little energy, they don't move very fast. However when the temperature, kinetic energy, is increased, the ping-pong balls move at a much faster pace.

8 Pressure can be defined as the force which acts on an object due to a gas. The SI unit for pressure is the pascal (N/m2). Other measurements for pressure are the standard atmosphere and the torr, where 101,325 Pa = 1 atmosphere (atm) = 760 torr.

9 Any gas inside a container which has kinetic energy will exert a pressure on the outer walls of that container by colliding and rebounding due to the random motion of gases. An increase in the number of collisions per second or an increase in the force of the collisions will increase the pressure exerted by the gas on the container.

10 ROBERT BOYLE Boyle's Law PV=k

11 Boyle's Law states that when the temperature and the number of particles of a sample of gas are held constant, its volume is inversely proportional to the pressure applied. P1 V1 = P2 V2

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13 Graph of the inverse relationship between pressure & volume of gases - forms a hyperbola © Microsoft Corporation. All Rights Reserved.

14 Charles's Law V/T = C Jacques Charles investigated the relationship between the Volume of a gas and how it changes with temperature.

15 This law states that volume temperature are directly related. When the number of particles and pressure are held constant, the temperature increases and decreases with the volume V1 / T1 = V2 / T2

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17 TEMPERATURE VOLUMEVOLUME 0 K

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19 GAS LAWS POP QUIZ 1. IF A GAS THAT OCCUPIES A VOLUME OF 2L AT A PRESSURE OF 760 torr IS ALLOWED TO EXPAND TO A VOLUME OF 10L - WHAT IS THE GAS’S NEW PRESSURE? [assume constant temp] 2. IF THE SAME GAS AT 10L VOLUME IS AT 10 C, WHAT WOULD ITS NEW VOLUME BE IF IT IS HEATED TO 100 C? [assume constant pressure]

20 Gay Lussac's Law P/T = C Joseph Louis Gay-Lussac investigated the relationship between the Pressure of a gas and its temperature.

21 At constant Volume, the pressure of a gas sample is directly proportional to the Kelvin Temperature. The relationship is similar to the Volume-Temperature relationship (Charles Law). The mathematical statement is as follows: P1 / T1 = P2 / T2

22 TEMPERATURE PRESSUREPRESSURE 0 K

23 Combined Gas Law The math expression for the Combined Gas Law is as follows: P1 V1 / T1 = P2 V2 / T2

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25 Dalton's Law of Partial Pressures John Dalton studied the effect of gases in a mixture.

26 P total = P1 + P2 + P3 +...Pn Dalton maintained that since there was an enormous amount of space between the gas molecules within the mixture that the gas molecules did not have any influence on the motion of other gas molecules, therefore the pressure of a gas sample would be the same whether it was the only gas in the container or if it were among other gases.

27 STP STANDARD TEMPERATURE = 0 C OR 273 K STANDARD PRESSURE = 1 atm OR 760 torr or 760 mm Hg

28 Water can be decomposed by an electric current into two volumes of Hydrogen gas, and one volume of Oxygen -- a simple whole number ratio of 2:1.

29 Lorenzo Romano Amedeo Carlo Avogadro di Quareqa e di Carreto - Avogadro for short. In 1811 he proposed his now famous hypothesis that equal volumes of gases, at the same temperature and pressure, contain equal numbers of molecules.

30 Notice that each container has the same number of molecules in it. The ratio of the volumes is 2 hydrogen to 1 oxygen to 2 water, and there is nothing left over.

31 LIQUID / GAS TRANSITION VAPOR PRESSURE - some liquid molecules can gain enough kinetic energy to break their intermolecular bonds and become a vapor which exerts pressure on the container. Termed - evaporation - increases rate with increased temp. - table O

32 DIFFUSION The molecular particles of gas are much more distant from one another than either liquid or solid particles are to each other. That is why gases are transparent. Light can pass through the relatively large spaces between the molecules of gas without any distortion.

33 Liquids distort light more so because the particles are closer,and the light passing through a liquid can be deflected more easily. If a gas possessing an odor such as Ammonia were allowed to escape an open bottle, it would not take but a few seconds for the detectable odor of Ammonia to be detected throughout the room. Ammonia gas molecules having a great deal of space between the particles of Ammonia and air could travel at a faster rate.

34 The speed or rate of diffusion is also affected by the mass of the particles. It stands to reason that the heavier a gas is the slower it will be able to move.

35 MATTER & ENERGY REVIEW ACTIVITY CREATE - A - VISUAL DEVICE 1. MUST USE AT LEAST 1 REGULAR SIZE PIECE OF CONSTRUCTION PAPER 2. AESTICHALLY PLEASING 3. USE MIND-MAP DESIGN OR FLOW CHART DESIGN 4. MUST INCLUDE THE FOLLOWING ITEMS: - PHASE CHANGE DIAGRAM - ALL 5 GAS LAWS - WITH CALCULATIONS - HEAT CALCULATIONS - DEFINITIONS (COMPOUNDS, ELEMENTS, MIXTURES, ETC.)


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