1 7. The kinetic theory of gases An ideal gas is one in which we can consider the forces between its particles as not significant. The scientific study of gases led to a theor y being established . It explains the laws of gases and predicts their behaviour. It is called the kinetic theor y of gases, and is a result of the work of James C. Maxwell and Ludwig E. Boltzmann in the 19th centur y. 21 Imagine that the particles of gases are little balls. Work like a scientist. Prepare information cards with drawings that explain each of the gas laws. KINETIC THEORY OF GASES The volume the particles occupy is much lower than the volume available in the container. We can assume the volume the gas occupies is the capacity of the container (unlike liquids or solids). The pressure exerted by the gas is the measure of the number of collisions per second of its particles against the walls of the container. There are no bonding forces between the particles in a gas. This is why they move with total freedom. Gas particles move in a straight line. When they hit another particle or the walls of the container, they move in another direction, but at the same speed. The collision is completely elastic, with no loss of energy. The speed of gas particles is proportional to their absolute temperature. The greater the speed, the higher the temperature. Gases are made up of very small particles that are separated from each other and move throughout the container. Absolute zero (0 K) is the temperature at which gas particles stop moving. It is the lowest temperature possible. This is the start of the Kelvin scale, which only has positive temperature values. T = 1000 K T = 300 K T = 0 K T = -273.15 °C The temperature increases The speed of the particles increases T = 26.85 °C T = 726.85 °C 6 4 2 1 5 3 Collision against the walls ® pressure Container Gas particles CHALLENGE 21
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