Chapter 13 States of Matter In this chapter you will: Explain the expansion and contraction of matter caused by changes in temperature . Apply Pascal’s, Archimedes’, and Bernoulli’s principles in everyday situations .
Chapter 13 Sections • Section 13.1: Properties of Fluids • Section 13.2: Forces within Liquids • Section 13.3: Fluids at Rest and in Motion • Section 13.4: Solids
Section 13.1 Properties of Fluids • Objectives • Describe how fluids create pressure. • Calculate the pressure, volume, and number of moles of a gas. • Compare gases and plasma.
INTRODUCTION • Fluid – any material that flows and offers little resistance to a change in its shape when under pressure. Liquids, gases, and plasma are fluids. • Most of our life is spent in the 2 fluid states of liquid (water for example) and gas (we live and breathe in the gaseous atmosphere).
PRESSURE • Fluid – any material that flows and offers little resistance to a change in its shape when under pressure. They have no definite shape of their own. Liquids, gases, & plasma are fluids • Kinetic Molecular Theory – this theory is based on the assumption that matter is made up of many tiny particles that are always in motion. In a hot body the particles move faster and thus have a higher energy than particles in a cooler body. • The Kinetic Molecular Theory is based on 3 simplified assumptions • Gases are made up of a large number of very small particles. • The particles are in constant, random motion. • The particles make perfectly elastic collisions with the walls of the container that hold them.
PRESSURE • Pressure – the force on a surface divided by the area of the surface. The force on a unit surface area. (or) Force per unit area. Unit for pressure is the PASCAL. Equation P = F / A • Pascal – unit for pressure. Its abbreviation is Pa. It is equal to one Newton per square meter (m2); N/m2. • The Pascal is a small unit so kilopascal is often used (kPa) • P = F / A Pressure = Force divided by Area • If you stand on a frozen lake the pressure is greater than if you lay on it since the surface area is smaller. So if you were trying to get someone that fell through the ice you should lay down & slide out not walk out. • Earth’s pressure at Sea Level is about 100,000 Pa (100 kPa)
PRESSURE • Example 1 p. 343 • 19.3 cm2 * (__1 m__)2 = 19.3 *__1___ = .00193m2 • (100 cm )2 10000 • ⅔(19.3) = 12.867 cm2 = .0012867 m2 (since only 2 of 3 legs are down) • a. P = F / A b. P = F / A • P = 405 / .00193 P = 405 / .0012867 • P = 209,844.56 Pa P = 314,758.685 Pa • Skip Practice Problems # 1-5 p. 344
THE GAS LAWS • Boyle’s Law – it is named for 17th century chemist and physicist Robert Boyle. It states that for a fixed sample of gas at constant temperature, the volume of the gas varies inversely with the pressure. P1V1 = P2V2. • Charles’ Law – named for Jacques Charles. It states that the volume of a sample of gas varies directly with its KELVIN temperature. V1 = V2 T1 T2 • Combined Gas Law – is a combination of Boyle’s Law and Charles’ Law. It states for a fixed amount of an ideal gas, the pressure times the volume divided by the KELVIN temperature equals a constant. P1V1 = P2V2 T1 T2
THE GAS LAWS • The combined gas law reduces to Boyle’s Law under conditions of constant temperature and to Charles’ law under conditions of constant pressure. • You use the kinetic molecular theory to discover how the constant in the combined gas law depends on the number of particles N. • If the number of particles increases the number of collisions increase and increases the pressure. If the number of particles decreases the number of collisions decrease and decreases the pressure. • You can conclude that the constant in the combined gas law equation is proportional to N _PV = kN T • Boltzmann’s Constant – the constant k in the equation above. It has a value of 1.38 * 10-23 Pa*m3/K.
THE GAS LAWS • Mole – is equal to 6.022 * 1023 particles. It is abbreviated as mol and is represented by “n”. • Avogadro’s Number - 6.022 * 1023. It is numerically equal to the number of particles in a sample of matter whose mass equals the molar mass of the substance. • If you use moles instead of the number of particles it changes the Boltzmann’s constant. This new constant is abbreviated “R” and has the value 8.31 Pa*m3 / (mol*K). • Ideal Gas Law – states for an ideal gas, the pressure times the volume is equal to the number of moles multiplied by the constant R and the KELVIN temperature. PV = nRT • The ideal gas law predicts behavior of gases very well, except under conditions of high pressure or low temperature.
THE GAS LAWS • Example 2 p. 346 • a. P1V1 = P2V2b. PV = nRT T1 T2 101300(.02) = n8.31(273) 101.3(20) = 145V 2026 = 2268.63n 273 120 .893 mol = n 243120 = 39585V c. m = Mn 6.142 L = Vm = 39.9(.893) m = 35.633 g • Skip Practice Problems #6-9 p. 347
THERMAL EXPANSION • Gases expand as their temperatures increase. • When heated all forms of matter generally become less dense and expand to fill more space. • Thermal Expansion – a property of all forms of matter that causes the matter to expand, becoming less dense, when heated. • Thermal expansion has many useful applications, such as circulating air in a room. • When the air near the floor of a room is warmed, gravity pulls down the denser, colder air from near the ceiling, which pushes the warmer air upward. • This circulation of air within a room is called a convection current. • When a liquid is heated, particle motion causes these groups to expand in the same way that particles in a solid are pushed apart. • The spaces between groups increase. As a result, the whole liquid expands.
THERMAL EXPANSION • With an equal change in temperature, liquids expand considerably more than solids, but not as much as gases. • You know that matter expands as it is heated. • Based on which you might predict that ice would be more dense than water, and therefore, it should sink. • However, when water is heated from 0°C to 4°C, instead of expanding, it contracts as the forces between particles increase and the ice crystals collapse. • The practical result is that water is most dense at 4°C and ice floats. • This fact is very important to our lives and environment. If ice sank, lakes would freeze from the bottom each winter and many would never melt completely in the summer.
PLASMA • Plasma – a gaslike, fluid state of matter made up of negatively charged electrons and positively charged ions that can conduct electricity. It makes up most of the matter of the universe such as stars. The difference between gas and plasma is plasma can conduct electricity. • Skip 13.1 Section Review p. 348