Chapter 10Section 1: The Kinetic-Molecular Theory of Matter●Kinetic molecular ○The kinetic-molecular theory: based on the idea that particle of matter are always in motion●The Kinetic Molecular Theory of Gases○Ideal gas: a hypothetical gas that perfectly fits all the assumptions of the kinetic-molecular theory○The kinetic molecular theory is based on the following five assumptions■1. Gases consist of large numbers of tiny particles that are far apart relative to their size●Most of the volume occupied by a gas is empty space (Multiple Choice Question)■2. Collisions between gas particles and between particlesand container walls are elastic collisions ●An elastic collision is one in which there is no net loss of total kinetic energy■3. Gas particles are in continuous, rapid, random motion. They therefore possess kinetic energy, which is energy of motion■4. There are no forces of attraction between gas particles■5. The temperature of a gas depends on the average kinetic energy of the particles of the gas●The kinetic energy of any moving object is given by the following equation:●KE = 1/2mv2○All gases at the same temp have the same average kinetic energy○At the same temp, lighter gas particles have higher average speeds than do heavier gas particles■Hydrogen molecules will have a higher speed than oxygen molecules●The Kinetic-Molecular Theory and the Nature of Gases○The kinetic-molecular theory applies only to ideal gases○Many gases behave nearly ideally if pressure is no very high
○Expansion■Gases do no have a definite shape or a definite volume●They completely fill any container in which they are enclosed●Gas particles move rapidly in all directions (assumption 3) without significant attraction between them (assumption 4)○Fluidity■Because the attractive forces between gas particles are insignificant (assumption 4), gas particles glide easily past one another●Because liquids and gases flow, they are both referred to asfluids. ○Low density■The density of a gaseous substance at atmospheric pressure is about 1/1000 the density of the same substance in the liquid or solid state●The reason is that the particles are so much fartherapart in the gaseous state (assumption 1).○Compressibility■During compression, the gas particles, which are initiallyvery far apart (assumption 1), are crowded closer together○Diffusion and effusion■Gases spread out and mix with one another, even without being stirred●The random and continuous motion of the gas molecules (assumption 3) carries them throughout the available space●Such spontaneous mixing of the particles of two substances cause by their random motion is called diffusion.