# Gases

Apr. 13, 2015
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### Gases

• 1. Gases -Natural law -Boyle’s law -Pressure -Kinetic theory of matter -Charles’s law -Absolute zero -Adiabatic
• 2. Natural law • When scientists observe nature they come out with laws these laws don’t change in the same condition. • Such generally observed behavior is formulated into a statement called a nature law. • For example, after observing the chemical reaction and finding that the amount of energy that comes from reaction don’t just disappear they came out with the law of conservation of mass and it’s a Natural law • Finally the natural law is : a concise verbal or mathematical statement of a relation that is always the same under the same conditions.
• 3. Pressure • Gases uniformly fills any container, is easily compressed and have law densities. • Gases also perform a pressure on its surrounding because they have mass. • For example the atmospheric pressure is caused by gases because they are pulled to the center of the earth by the gravitational force. • The pressure can be calculated by dividing the force by the area which the force is exerted on. • The main unit for calculating pressure is the pascal and it’s equal to 1 newton divided by 1 meter.
• 4. Boyle’s Law • Boyle is a scientist who studied the relationship between the pressure and the volume of a gas. • For a given amount of a gas at a constant temperature, the volume of the gas varies inversely with it’s pressure. That means as the volume of the gas increase the pressure of the gas decrease and the contrary is true. • P × V = K , where K is a constant. • You can also state the law as : V ∼ 1/P or V = K/P
• 5. Kinetic Theory of Matter • This theory states that the particles that makes up matter (atoms and molecules) are always in constant rapid motion. • The kinetic molecular theory of gases also states that the particles of a gas are very far apart relative to their size. • The kinetic-molecular theory considers collisions of gas particles to be perfectly elastic; that is, energy is completely transferred during collisions. The total energy of the system, however, remains constant.
• 6. Charles’s Law • Charles came after Boyle and he started his work in gas by a simple experiment. • He discovered a law that states that for a fixed amount of gas at a constant pressure, the volume of the gas varies directly with the pressure, that means the volume of gas increases as the temperature increases. • V ∼ T or V= K× T where V is the volume and k is constant
• 7. Absolute zero • Charles’s law defines the relationship between gases’ volume and temperature if we did an experiments on several gases to explain the law we will see this a figure similar to the opposite one. • You can see that the volumes of all gases extrapolate at the same temperature and it’s -273 °C • This temperature is called the absolute zero in which the substance has no volume. This temperature is equal to 0 K (Kelvin) K = °C + 273
• 8. Adiabatic • An adiabatic process is one that occurs without transfer of heat or matter between a system and its surroundings.
• 9. Charles’s Law experiment . Charles discovered that a quantity of gas kept at a constant pressure expands as it warms and contracts as it cools. The equipment used by Charles was very similar to that employed by Boyle. A quantity of gas was trapped in a glass tube that was sealed at one end. This tube was immersed in a water bath. By changing the temperature of the water, Charles was able to observe the change in volume of the gas. The pressure was held constant by adjusting the height of mercury so that the two columns of mercury had equal height, and so the pressure was always equal to the atmospheric pressure. This allowed Charles to examine the effect of only one variable, temperature, on the volume of a gas. Through repeated experimentation with many different gases, Charles found that there was a relationship between the volume of a gas and the temperature of that gas.