Chapter 5 - Gases and the Kinetic Energy Theory

  • The water inside a kernel of popcorn vaporizes at 180°C, and the resultant gas expands owing to heat until the pressure exceeds nine times that of the atmosphere.
  • The shell ruptures, and the carbohydrates and proteins in the maize form an inflated, frothy mass.

   Gas, Liquid, and Solid

  • The connection between a gas's pressure, volume, and temperature are also vital to scuba divers, hot-air balloon operators, and bread bakers, and it is at work during the inflation of a car's airbag, the operation of a car engine, and a variety of other real-world applications.
  • Throughout history, people have been investigating the behavior of gases and various states of matter.
  • In reality, three of the ancient Greeks' four "elements" were air (gas), water (liquid), and soil (solid). Nonetheless, despite millennia of observations, many questions remain unanswered.
  • Gases are all around us. Our atmosphere is a colorless, odorless mixture of 18 gases, several of which—O2, N2, H2O vapor, and CO2—play important roles in the environment's life-sustaining redox processes. Several other gases, such as chlorine and ammonia, are also important in manufacturing.
  • The chemical activity specific to each gas is ignored in favor of focusing on the physical behavior shared by all gases.
  • Under the right pressure and temperature circumstances, most substances may exist as a solid, a liquid, or a gas.
  • Because its particles are wide apart and move randomly, a gas takes on the shape of a container and fills it. Because its particles are so small, a liquid takes on the form of a container to the degree of its volume.
  • They remain near yet have the freedom to roam around each other. Because its particles have a set form, a solid has a definite shape regardless of the container shape, is close together, and tightly kept in place.
  • Several more characteristics separate gases from liquids and solids: The volume of a gas varies dramatically as pressure increases.
  • When a gas sample is confined to a variable volume container, such as a cylinder with a piston, increasing the force on the piston reduces the gas volume; therefore, gases are compressible—the gas particles may be pushed closer together into a smaller volume.
  • When the external force is removed, the volume can be increased again. Compressed air with a jackhammer smashes rock and cement; compressed air in tires raises the weight of an automobile. Liquids and solids, on the other hand, have extremely little or no compressibility.
  • The volume of a gas changes dramatically with temperature. When a gas sample is heated, it expands; when it is cooled, it contracts.
  • Gases have a volume change that is 50 to 100 times higher than liquids or solids. the growth that takes place when rapidly heated gases may have dramatic consequences, such as launching a rocket into space and commonplace ones, such as popping corn.
  • Gases move extremely quickly. Gases move significantly faster than liquids and solids.
  • This characteristic allows gases to be carried more readily via pipes, but it also has a negative impact.
  • This means they leak more quickly via tiny holes and fractures.
  • The densities of gases are low. Gas density is often measured in grams per liter (g/L), whereas liquid and solid densities are measured in grams per milliliter (g/mL), which is almost 1000 times as dense (see Table 1.5).
  • For instance, have a look at the table comparing the densities of a gas, liquid, and solid at 20°C and normal pressure in the atmosphere. When a gas cools, its density rises because its volume decreases, when the temperature drops from 20°C to 0°C, the density of O2(g) rises from 1.3 to 1.4 g/L.
  • Gases can combine to produce a solution in any proportion. Air is a mixture of 18 gases. However, two liquids may or may not form a solution: water and ethanol, but not water and gasoline.
  • Unless two substances are melted, they will not create a solution and combine while liquids, then allowed to harden (as in the alloying process).
  • These macroscopic properties—changing volume with pressure or temperature, tremendous ability to flow, low density, and capacity to form solutions, similar to how a gas entirely fills a container—arise because the particles in a gas are considerably further apart than those in a liquid or a solid at normal pressures.
  • The volume of a gas can be dramatically changed by varying the applied force or temperature.
  • For liquids and solids, the corresponding changes are significantly less. Gases are less dense and flow more easily than liquids and solids.
  • Gases can combine in any proportion to produce solutions; liquids and solids, on the other hand, can not. Differences in physical states are caused by a larger average distance between particles in gas as opposed to a liquid or solid.
  • Gas particles travel at relatively high speeds within a container, hitting often the container's walls.
  • The force of these collisions with the walls, known as gas pressure, is what allows you to blow up a balloon or pump up a tire. The force exerted per unit of the charge a bond surface area is denoted as pressure (P):
      * pressure = force/area
  • The gases in the atmosphere exert a consistent force (or weight) on all surfaces, resulting in atmospheric pressure, which is generally around 14.7 pounds per square inch (lb/in2); psi) of surface pressure. As a result, a pressure of 14.7 lb/in2 is obtained.
  • The pressure on the exterior of your room (or your body) matches the pressure on the inside.