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  2. Chapter Twelve: Properties of Matter • 12.1 Properties of Solids • 12.2 Properties of Fluids • 12.3 Buoyancy

  3. Chapter 12.1 Learning Goals • Distinguish chemical properties from physical properties of matter. • Identify differences between crystalline and amorphous solids. • Explain how the arrangement of atoms and molecules in solids determines their properties.

  4. Key Question: How do solids and liquids differ? Investigation 12A Mystery Material

  5. 12.1 Properties of Solids • Different kinds of matter have different characteristics. • Characteristics that can you observe directly are called physical properties. • Physical properties include color, texture, density, brittleness, and state (solid, liquid, or gas). Ex. Iron is solid at room temp.

  6. 12.1 Properties of Solids • A physical changeis any change in the size, shape, or phase of matter in which the identity of a substance does not change. • For example, when water is frozen, it changes from a liquid to a solid.

  7. 12.1 Properties of Solids • Properties that can only be observed when one substance changes into a different substance are called chemical properties. • Any change that transforms one substance into a different substance is called a chemical change. Iron reacts with oxygen to form iron oxide. Ex. If you leave a nail outside, it rusts.

  8. 12.1 Properties of Solids The density of a solid material depends on two things: • the individual mass of each atom or molecule, • how closely the atoms or molecules are packed together. Carbon atoms in diamond are packed very tightly.

  9. 12.1 Properties of Solids • Paraffin wax is also mostly carbon, but its density is only 0.87 g/cm3. • Paraffin’s carbon atoms are mixed with hydrogen atoms in long molecules that take up more space. The density of paraffin is low compared to diamond.

  10. 12.1 Properties of Solids The atoms or molecules in a solid are arranged in two ways. • If the particles are arranged in an orderly, repeating pattern, the solid is crystalline. • If the particles are arranged in a random way, the solid is amorphous.

  11. 12.1 Properties of Solids • Examples of crystalline solids include salts, minerals, and metals.

  12. 12.1 Properties of Solids • Metals don’t look like “crystals” because solid metal is made from very tiny crystals fused together in a jumble of different orientations.

  13. 12.1 Properties of Solids • The atoms or molecules in amorphous solids are randomly arranged. • Examples of amorphous solids include rubber, wax, and glass.

  14. 12.1 Mechanical properties • “Strength” describes the ability of a solid object to maintain its shape even when force is applied.

  15. 12.1 Mechanical properties • Tensile strength is a measure of how much stress a material can withstand before breaking.

  16. 12.1 Mechanical properties • Hardness measures a solid’s resistance to scratching. How might you compare the hardness of these two metals?

  17. 12.1 Mechanical properties • Elasticitydescribes a solid’s ability to be stretched and then return to its original size. • Brittlenessis defined as the tendency of a solid to crack or break before stretching very much.

  18. 12.1 Mechanical properties • A ductile material can be bent a relatively large amount without breaking. • The ductility of many metals, like copper, allow then to be drawn into wire.

  19. 12.1 Mechanical properties • Malleability measures a solid’s ability to be pounded into thin sheets. • Aluminum is a highly malleable metal.

  20. 12.1 Mechanical properties • Almost all solid materials expand as the temperature increases. • The increased vibration makes each particle take up a little more space, causing thermal expansion. Sidewalks and bridges have grooves that allow for thermal expansion.

  21. Chapter Twelve: Properties of Matter • 12.1 Properties of Solids • 12.2 Properties of Fluids • 12.3 Buoyancy

  22. Chapter 12.2 Learning Goals • Explain how pressure is created in fluids. • Discuss differences between the density of solids and fluids. • Apply Bernoulli’s principle to explain how energy is conserved in fluids.

  23. 12.2 Properties of Fluids • A fluid is defined as any matter that flows when force is applied. • Liquids like water or silver are kinds of fluid.

  24. 12.2 Pressure • A force applied to a fluid creates pressure. • Pressure acts in all directions, not just the direction of the applied force.

  25. 12.2 Forces in fluids • Forces in fluids are more complicated than forces in solids because fluids can change shape.

  26. 12.2 Units of pressure • The units of pressure are force divided by area. • One psi is one pound per square inch.

  27. 12.2 Units of pressure • The S.I. unit of force is the pascal. • One pascal (unit of force) is one newton of force per square meter of area (N/m2).

  28. 12.2 Pressure • If your car tires are inflated to 35 pounds per square inch (35 psi), then a force of 35 pounds acts on every square inch of area inside the tire. What might happen if you over-inflate a tire?

  29. 12.2 Pressure • On the microscopic level, pressure comes from collisions between atoms. • Every surface can experience a force from the constant impact of trillions of atoms. • This force is what we measure as pressure.

  30. 12.2 Pressure • In a car engine high pressure is created by an exploding gasoline-air mixture.

  31. 12.2 Energy conservation and Bernoulli’s Principle • Streamlinesare imaginary lines drawn to show the flow of fluid. • Bernoulli’s principle tells us that the energy of any sample of fluid moving along a streamline is constant.

  32. 12.2 Bernoulli’s Principle • Bernoulli’s principle says the three variables of height, pressure, and speed are related by energy conservation.

  33. 12.2 Three Variables and Bernoulli’s Principle • If one variable increases along a streamline, at least one of the other two must decrease. • For example, if speed goes up, pressure goes down.

  34. 12.2 The air foil • One of the most important applications of Bernoulli’s principle is the airfoil shape of wings on a plane. • When a plane is moving, the pressure on the top surface of the wings is lower than the pressure beneath the wings. • The difference in pressure is what creates the lift force that supports the plane in the air.

  35. 12.2 Hydraulics and Pascal’s Principle • Hydraulic lifts and other hydraulic devices use pressure to multiply forces and do work. • The word hydraulicrefers to anything that is operated by a fluid under pressure. • Hydraulic devices operate on the basis of Pascal’s principle, named after Blaise Pascal.

  36. 12.2 Hydraulics and Pascal’s Principle • Pascal’s principle states that the pressure applied to an incompressible fluid in a closed container is transmitted equally in all parts of the fluid. • An incompressible fluid does not decrease in volume when pressure is increased.

  37. 12.2 Hydraulics and Pascal’s Principle • A small force exerted over a large distance is traded for a large force over a small distance.

  38. 12.2 Pressure • Pressure is force divided by area.

  39. 12.2 Force • You can calculate the force exerted if you know the pressure and area.

  40. Solving Problems • On a hydraulic lift, 5 N of force is applied over an area of 0.125 m2. • What is the output force if the area of the larger cylinder is 5.0 m2?

  41. Solving Problems • Looking for: • …output force • Given • …input force = 5 N; input area = .125 m2 ; output area = 5 m2 • Relationships: • Pressure = Force Force = P x A Area

  42. Solving Problems • Solution • Solve for pressure using input force. • Pressure = 5 N = 40 N/m2 .125m2 • Use Pascal’s law principle and use equivalent pressure to solve for output force. • Force = 40 N x 5 m2 = m2 200 N

  43. 12.2 Viscosity • Viscosity is the property of fluids that causes friction. • Viscosity is determined in large part by the shape and size of the particles in a liquid.

  44. 12.2 Viscosity and temperature • As the temperature of a liquid increases, the viscosity of a liquid decreases. • Increasing the kinetic energy of the substance allows the particles to slide past one another more easily.

  45. Key Question: What is the maximum load a boat can hold before sinking? How is the maximum load affected by the density of the water in which the boat floats? Investigation 12C Density of Fluids

  46. Chapter Twelve: Properties of Matter • 12.1 Properties of Solids • 12.2 Properties of Fluids • 12.3 Buoyancy