Chemistry – Liquids
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Which of these observations are not explained by kinetic-molecular theory? --When a gas is heated, it expands. --At very low temperatures, gases expand less for a given pressure change than they do at high temperatures. --If the volume of a gas decreases, its pressure increases at constant temperature. --When gas is added to a rigid container, the pressure inside the container increases
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At very low temperatures, gases expand less for a given pressure change than they do at high temperatures.
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takes the shape of its container:
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liquid
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fills all available space:
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gas
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can be poured:
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liquid
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maintains its shape:
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solid
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is compressible:
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gas
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has a fixed volume:
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liquid and solid
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Viscosity
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The thickness or resistance to flow of a liquid
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Surface tension
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The tendency for a liquid surface to resist penetration
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Surfactant
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Can reduce surface tension
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Dissolve
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When a solid, liquid, or gas becomes intergrated into a host liquid
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Msicible Liquids
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Dissolve in each other
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Immiscible Liquids
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Cannot dissolve in each other
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The forces between water molecules are stronger than the forces between ethanol molecules. Which liquid would probably be most difficult for an insect to walk on? Explain your answer.
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Include: --An insect would have an easier time walking on the surface of water than on the surface of ethanol. --Water's stronger intermolecular forces lead to higher surface tension. --Higher surface tension allows water to support the insect.
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A student places a small amount of water in a glass dish and then carefully places a small paperclip on the surface of the water. The paperclip floats. What happens if the student adds a drop or two of dish soap to the water? Explain your answer.
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Include: --Adding soap makes the paperclip fall through the water to the bottom of the dish. --Soap is a surfactant. --Surfactants reduce the surface tension of a liquid. --The surface tension of water is what supported the paper clip.
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A sample of water is mixed with a surfactant. What will most likely happen to the viscosity of the water? Explain your answer.
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Include: --The viscosity of the water will decrease. --Surfactants disrupt intermolecular forces within a liquid. --Viscosity is directly related to intermolecular forces. --If intermolecular forces are decreased, viscosity should also decrease.
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Describe two uses of surfactants. At least one must be something that was not described in the passage. For each example, explain how the effects of the surfactant make it useful.
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Include: --Surfactants are used to help improve gas exchange in the lungs of premature infants. --Surfactants are used to prevent salad dressings from separating. --Pulmonary surfactants reduce the surface tension of the gas exchange surfaces in the lungs, allowing gases to diffuse more easily. --Surfactants help the water molecules and oil molecules in salad dressings interact and mix.
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What happens when a solid is dissolved into a liquid?
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Solid particles become evenly dispersed among liquid particles.
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Which process most likely takes place when the kinetic energy of molecules overcomes the intermolecular forces?
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boiling
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Which molecules would most likely cause a liquid to have the lowest viscosity?
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small, nonpolar molecules
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Liquids and solids are referred to as \"condensed phases\" because the attractive forces
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leave little space between the molecules.
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Melting can be best described as a process in which molecules
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gain enough kinetic energy to get past each other.
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What happens as a result of the kinetic energy of the particles in a liquid being comparable with the intermolecular attractions between the particles?
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The particles move enough that they are not fixed in place, and the liquid can flow.
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Valerie wants to examine the properties of a thick liquid but is finding it difficult to pour the liquid into a beaker. She needs to finish her investigation before the end of class. Which method will allow her to pour the liquid easily?
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applying heat to the liquid
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Which postulate of the kinetic-molecular theory applies to the particles of a liquid?
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They have enough kinetic energy to easily slide by each other.
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Glycerol boils at a higher temperature than water. What does this indicate about the attractive forces of glycerol?
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They are stronger than those in water.
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Why are liquids well suited for hydraulics?
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Liquids are incompressible.
