Section 13.4 Solids Objectives  Relate the properties of solids to their structures.  Explain why solids expand and contract when the temperature changes.  Calculate the expansion of solids.  Explain the importance of thermal expansion.

INTRODUCTION Solids differ from liquids in that they are stiff, they can be cu in pieces, and they retain their shape. You can push on solids but if you try to push on a liquid your hand will move through it.

SOLID BODIES Crystal Lattice – structure of solid consisting of regular arrangements of atoms. Amorphous Solids – solids that have no long range order meaning no crystal structure. The particles are fixed but the pattern is variable. They have definite volume and shape but no regular crystal structure. Amorphous solids also are classified as viscous, or slowly flowing, liquids. As a liquid becomes a solid, its particles usually fit more closely together than in the liquid state, making solids more dense than liquids.

SOLID BODIES However, water is an exception because it is most dense at 4°C. Water is also an exception to another general rule. For most liquids, an increase in the pressure on the surface of the liquid increases its freezing point. Because water expands as it freezes, an increase in pressure forces the molecules closer together and opposes the freezing. Therefore, higher pressure lowers the freezing point of water very slightly. Elasticity – ability of an object to return to its original shape after deforming forces are removed. It depends on the electromagnetic forces that hold the particles of a substance together. Malleability – the ability of a solid to be rolled into a thin sheet Ductility – the ability of a solid to be drawn into a wire.

THERMAL EXPANSION OF SOLIDS Thermal Expansion – increase in length or volume of an object due to change in temperature. Most objects will expand when heated and contract when cooled. Coefficient of Linear Expansion – change in length divided by original length and by temperature change.  =  L / L1*  T Coefficient of Volume Expansion – change in volume divided by original volume and by temperature change.  =  V / V1*  T

THERMAL EXPANSION OF SOLIDS Table 13.2 p. 361

THERMAL EXPANSION OF SOLIDS Example 4 p. 363  =  L / L1*  T  =.0017 / (1.6 * (84 – 21) )  C-1 Skip Practice Problems p. 362 Skip 13.4 Section Review

SWIMMING UNDER PRESSURE Ships can float because the hull is hollow and large enough so the average density of the ship is less than the density of water. You can notice that a ship filled with cargo will be submerged more than a ship with no cargo. Example 3 p. 356 a. F buoyant = ρVg b. F g = mg = ρVg F apparent = F g – F b F buoyant = 1000(.001)(9.8) Fg = 2700(.001)(9.8) Fa = – 9.8 F buoyant = 9.8 N Fg = N Fa = N Skip Practice Problems p. 356

FLUIDS IN MOTION: BERMOULLI’S PRINCIPLE Bernoulli’s Principle – states that as the velocity of a fluid increases, the pressure exerted by that fluid decreases. Or when a fixed quantity of fluid flows, the pressure is decreased when the velocity increases. There are many common applications of Bernoulli’s principle, such as paint sprayers and perfume bottles. A gasoline engine’s carburetor, which is where air and gas are mixed, is another common application of Bernoulli’s principle. Part of the carburetor is a tube with a constriction, as shown in figure 13-16b. Streamlines – lines representing the flow of fluids around objects. Skip 13.3 Section Review