12. 1 Properties of Solids


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12.1 Properties of Solids

  • 12.1 Properties of Solids

  • 12.2 Properties of Fluids

  • 12.3 Buoyancy



Different kinds of matter have different characteristics.

  • 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).



A physical change is any change in the size, shape, or phase of matter in which the identity of a substance does not change.

  • A physical change is 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.



Properties that can only be observed when one substance changes into a different substance are called chemical properties.

  • 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.



The density of a solid material depends on two things:

  • 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.



Paraffin wax is also mostly carbon, but its density is only 0.87 g/cm3.

  • 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 atoms or molecules in a solid are arranged in two ways.

  • 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.



Examples of crystalline solids include salts, minerals, and metals.

  • Examples of crystalline solids include salts, minerals, and metals.



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

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



The atoms or molecules in amorphous solids are randomly arranged.

  • The atoms or molecules in amorphous solids are randomly arranged.

  • Examples of amorphous solids include rubber, wax, and glass.



Strength” describes the ability of a solid object to maintain its shape even when force is applied.

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



Tensile strength is a measure of how much stress a material can withstand before breaking.

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



Hardness measures a solid’s resistance to scratching.

  • Hardness measures a solid’s resistance to scratching.



Elasticity describes a solid’s ability to be stretched and then return to its original size.

  • Elasticity describes a solid’s ability to be stretched and then return to its original size.

  • Brittleness is defined as the tendency of a solid to crack or break before stretching very much.



A ductile material can be bent a relatively large amount without breaking.

  • 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.



Malleability measures a solid’s ability to be pounded into thin sheets.

  • Malleability measures a solid’s ability to be pounded into thin sheets.

  • Aluminum is a highly malleable metal.



Almost all solid materials expand as the temperature increases.

  • Almost all solid materials expand as the temperature increases.

  • The increased vibration makes each particle take up a little more space, causing thermal expansion.



A fluid is defined as any matter that flows when force is applied.

  • A fluid is defined as any matter that flows when force is applied.

  • Liquids like water or silver are kinds of fluid.



A force applied to a fluid creates pressure.

  • A force applied to a fluid creates pressure.

  • Pressure acts in all directions, not just the direction of the applied force.



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

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



The units of pressure are force divided by area.

  • The units of pressure are force divided by area.

  • One psi is one pound per square inch.



The S.I. unit of force is the pascal.

  • 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).



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.

  • 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.



On the microscopic level, pressure comes from collisions between atoms.

  • 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.



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

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



Streamlines are imaginary lines drawn to show the flow of fluid.

  • Streamlines are 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.



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

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



If one variable increases along a streamline, at least one of the other two must decrease.

  • 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.



One of the most important applications of Bernoulli’s principle is the airfoil shape of wings on a plane.

  • 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.



Viscosity is the property of fluids that causes friction.

  • 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.



As the temperature of a liquid increases, the viscosity of a liquid decreases.

  • 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.



Buoyancy is a measure of the upward force a fluid exerts on an object that is submerged.

  • Buoyancy is a measure of the upward force a fluid exerts on an object that is submerged.



The strength of the buoyant force on an object in water depends on the volume of the object that is underwater.

  • The strength of the buoyant force on an object in water depends on the volume of the object that is underwater.



Weight is a force, like any other pushing or pulling force, and is caused by Earth’s gravity.

  • Weight is a force, like any other pushing or pulling force, and is caused by Earth’s gravity.

  • It is easy to confuse mass and weight, but they are not the same.

  • Weight is the downward force of gravity acting on mass.



In the third century BC, a Greek mathematician named Archimedes realized that buoyant force is equal to the weight of fluid displaced by an object.

  • In the third century BC, a Greek mathematician named Archimedes realized that buoyant force is equal to the weight of fluid displaced by an object.

  • A simple experiment can be done to measure the buoyant force on a rock with a spring scale when it is immersed in water.





In air the buoyant force on the rock is 29.4 N.

  • In air the buoyant force on the rock is 29.4 N.





Buoyancy explains why some objects sink and others float.

  • Buoyancy explains why some objects sink and others float.



If you know an object’s density you can quickly predict whether it will sink or float.

  • If you know an object’s density you can quickly predict whether it will sink or float.



Average density helps determine whether objects sink or float.

  • Average density helps determine whether objects sink or float.

    • An object with an average density GREATER than the density of water will sink.
    • An object with an average density LESS than the density of water will float.




When they are completely underwater, both balls have the same buoyant force because they displace the same volume of water.

  • When they are completely underwater, both balls have the same buoyant force because they displace the same volume of water.





Use your understanding of average density to explain how steel boats can be made to float.

  • Use your understanding of average density to explain how steel boats can be made to float.



If you have seen a loaded cargo ship, you might have noticed that it sat lower in the water than an unloaded ship nearby.

  • If you have seen a loaded cargo ship, you might have noticed that it sat lower in the water than an unloaded ship nearby.

  • This means a full ship must displace more water (sink deeper) to make the buoyant force large enough to balance the ship’s weight.




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