13.1 The Nature of Gases > Chapter 13 States of Matter Al-NASR International School Lesson Design & Prepared by ShahRukh Younas LESSON 13.1 13.1 The Nature of Gases 13.1 The Nature of Gases > CHEMISTRY & YOU What factors most strongly affect the weather? Al-NASR International School LESSON 13.1 The atmosphere is a gas, and the factors that determine the behavior of gases— temperature and pressure—affect the weather in the atmosphere. Lesson Design & Prepared by ShahRukh Younas 13.1 The Nature of Gases > Kinetic Theory and a Model for Gases Kinetic Theory and a Model for Gases What are the three assumptions of the kinetic theory as it applies to gases? LESSON 13.1 Al-NASR International School Lesson Design & Prepared by ShahRukh Younas 13.1 The Nature of Gases > Kinetic Theory and a Model for Gases The word kinetic refers to motion. Al-NASR International School Lesson Design & Prepared by ShahRukh Younas LESSON 13.1 • The energy an object has because of its motion is called kinetic energy. 13.1 The Nature of Gases > Kinetic Theory and a Model for Gases The word kinetic refers to motion. • The energy an object has because of its motion is called kinetic energy. • The particles in a gas are usually molecules or atoms. Al-NASR International School Lesson Design & Prepared by ShahRukh Younas LESSON 13.1 • According to the kinetic theory, all matter consists of tiny particles that are in constant motion. 13.1 The Nature of Gases > Kinetic Theory and a Model for Gases The kinetic theory as it applies to gases includes the following fundamental assumptions about gases. The particles in a gas are considered to be small, hard spheres with an insignificant volume. – Between the particles, there is empty space. – No attractive or repulsive forces exist between the particles. Al-NASR International School Lesson Design & Prepared by ShahRukh Younas LESSON 13.1 – Within a gas, the particles are relatively far apart compared with the distance between particles in a liquid or solid. 13.1 The Nature of Gases > Kinetic Theory and a Model for Gases The kinetic theory as it applies to gases includes the following fundamental assumptions about gases. – Gases fill their containers regardless of the shape and volume of the containers. Bromine molecule – An uncontained gas can spread out into space without limit. Al-NASR International School Lesson Design & Prepared by ShahRukh Younas LESSON 13.1 The motion of particles in a gas is rapid, constant, and random. 13.1 The Nature of Gases > Kinetic Theory and a Model for Gases The kinetic theory as it applies to gases includes the following fundamental assumptions about gases. – The rapid, constant motion of particles in a gas causes them to collide with one another and with the walls of their container. Al-NASR International School Lesson Design & Prepared by ShahRukh Younas LESSON 13.1 The motion of particles in a gas is rapid, constant, and random. 13.1 The Nature of Gases > Kinetic Theory and a Model for Gases The kinetic theory as it applies to gases includes the following fundamental assumptions about gases. Al-NASR International School LESSON 13.1 The motion of particles in a gas is rapid, constant, and random. Lesson Design & Prepared by ShahRukh Younas 13.1 The Nature of Gases > Kinetic Theory and a Model for Gases The kinetic theory as it applies to gases includes the following fundamental assumptions about gases. – During an elastic collision, kinetic energy is transferred without loss from one particle to another. – The total kinetic energy remains constant. Al-NASR International School Lesson Design & Prepared by ShahRukh Younas LESSON 13.1 All collisions between particles in a gas are perfectly elastic. 13.1 The Nature of Gases > Describe an elastic collision between gas molecules. Al-NASR International School Lesson Design & Prepared by ShahRukh Younas LESSON 13.1 An elastic collision is one in which kinetic energy is transferred from one particle to another with no overall loss of kinetic energy. 13.1 The Nature of Gases > Gas Pressure How does kinetic theory explain gas pressure? Gas pressure results from the force exerted by a gas per unit surface area of an object. Al-NASR International School Lesson Design & Prepared by ShahRukh Younas LESSON 13.1 • Moving bodies exert a force when they collide with other bodies. 13.1 The Nature of Gases > Gas Pressure Gas pressure is the result of billions of rapidly moving particles in a gas simultaneously colliding with an object. • An empty space with no particles and no pressure is called a vacuum. Al-NASR International School Lesson Design & Prepared by ShahRukh Younas LESSON 13.1 • If no particles are present, no collisions can occur. Consequently, there is no pressure. 13.1 The Nature of Gases > Gas Pressure Air exerts pressure on Earth because gravity holds the particles in air within Earth’s atmosphere. • Atmospheric pressure decreases as you climb a mountain because the density of Earth’s atmosphere decreases as the elevation increases. Lesson Design & Prepared by ShahRukh Younas Al-NASR International School LESSON 13.1 • The collisions of atoms and molecules in air with objects results in atmospheric pressure. 13.1 The Nature of Gases > Gas Pressure A barometer is a device that is used to measure atmospheric pressure. • On top of Mount Everest, at 9000 m, the air exerts only enough pressure to support a 253-mm column of mercury. Al-NASR International School Vacuum 760 mm Hg (barometric pressure) Atmospheric pressure 253 mm Hg Sea level On top of Mount Everest Lesson Design & Prepared by ShahRukh Younas LESSON 13.1 • At sea level, air exerts enough pressure to support a 760-mm column of mercury.
