Chapter 8 Solutions

1
Chapter 8Solutions

• Properties of Water
• Solutions

2
Predict the water in the following foods

3
Predict the water in the following foods

• 88 water
• 94 water
• 85 water
• 86 water

4
Water in the Body

• water gain water loss
• liquids 1000 mL urine 1500 mL
• food 1200 mL perspiring 300 mL
• cells 300 mL exhaling 600 mL
• feces 100 mL
• Calculate the total water gain and water loss
• Total ______ mL
  _____ mL

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Water

• Most common solvent
• A polar molecule
• O? -
• a hydrogen bond
• H?
• H?

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Hydrogen Bonds Attract Polar Water Molecules

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ExploreSurface Tension

• Fill a glass to the brim with water
• How many pennies can you add to the glass without
  causing any water to run over?
• Predict _________________
• Actual _________________
• Explain your results

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Explore

• 1. Place some water on a waxy surface. Why do
  drops form?
• 2. Carefully place a needle on the surface of
  water. Why does it float? What happens if you
  push it through the water surface?
• 3. Sprinkle pepper on water. What does it do?
  Add a drop of soap. What happens?

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Surface Tension

• Water molecules within water hydrogen bond in all
  directions
• Water molecules at surface cannot hydrogen bond
  above the surface, pulled inward
• Water surface behaves like a thin, elastic
  membrane or skin
• Surfactants (detergents) undo hydrogen bonding

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Solute and Solvent

• Solutions are homogeneous mixtures of two or
  more substances
• Solute
• The substance in the lesser amount
• Solvent
• The substance in the greater amount

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Nature of Solutes in Solutions

• Spread evenly throughout the solution
• Cannot be separated by filtration
• Can be separated by evaporation
• Not visible, solution appears transparent
• May give a color to the solution

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Types of Solutions

• air O2 gas and N2 gas gas/gas
• soda CO2 gas in water gas/liquid
• seawater NaCl in water solid/liquid
• brass copper and zinc solid/solid

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Discussion

• Give examples of some solutions and explain why
  they are solutions.

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Learning Check SF1

• (1) element (2) compound (3) solution
• A. water 1 2 3
• B. sugar 1 2 3
• C. salt water 1 2 3
• D. air 1 2 3
• E. tea 1 2 3

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Solution SF1

• (1) element (2) compound (3) solution
• A. water 2
• B. sugar 2
• C. salt water 3
• D. air 3
• E. tea 3

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Learning Check SF2

• Identify the solute and the solvent.
• A. brass 20 g zinc 50 g copper
• solute 1) zinc 2) copper
• solvent 1) zinc 2) copper
• B. 100 g H2O 5 g KCl
• solute 1) KCl 2) H2O
• solvent 1) KCl 2) H2O

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Solution SF2

• A. brass 20 g zinc 50 g copper
• solute 1) zinc solvent 2)
  copper
• B. 100 g H2O 5 g KCl
• solute 1) KCl
• solvent 2) H2O

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Learning Check SF3

• Identify the solute in each of the following
  solutions
• A. 2 g sugar (1) 100 mL water (2)
• B. 60.0 mL ethyl alcohol(1) and 30.0 mL
• of methyl alcohol (2)
• C. 55.0 mL water (1) and 1.50 g NaCl (2)
• D. Air 200 mL O2 (1) 800 mL N2 (2)

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Solution SF3

• Identify the solute in each of the following
  solutions
• A. 2 g sugar (1)
• B. 30.0 mL of methyl alcohol (2)
• C. 50 g NaCl (2)
• D. 200 mL O2 (1)

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Like dissolves like

• A ____________ solvent such as water is needed
  to dissolve polar solutes such as sugar and ionic
  solutes such as NaCl.
• A ___________solvent such as hexane (C6H14) is
  needed to dissolve nonpolar solutes such as oil
  or grease.

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Learning Check SF4

• Which of the following solutes will dissolve in
  water? Why?
• 1) Na2SO4
• 2) gasoline
• 3) I2
• 4) HCl

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Solution SF4

• Which of the following solutes will dissolve in
  water? Why?
• 1) Na2SO4 Yes, polar (ionic)
• 2) gasoline No, nonnpolar
• 3) I2 No, nonpolar
• 4) HCl Yes, Polar

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Formation of a Solution

H2O
Hydration
Na
Cl-
Na
Dissolved solute
Cl-
H2O
Na
Cl-
solute
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Writing An Equation for a Solution

• When NaCl(s) dissolves in water, the reaction
  can be written as
• H2O
• NaCl(s) Na (aq) Cl- (aq)
• solid separation of ions in
  water

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Learning Check SF5

• Solid LiCl is added to some water. It dissolves
  because
• A. The Li ions are attracted to the
• 1) oxygen atom(??-) of water
• 2) hydrogen atom(?) of water
• B. The Cl- ions are attracted to the
• 1) oxygen atom(??-) of water
• 2) hydrogen atom(?) of water

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Solution SF5

• Solid LiCl is added to some water. It dissolves
  because
• A. The Li ions are attracted to the
• 1) oxygen atom(??-) of water
• B. The Cl- ions are attracted to the
• 2) hydrogen atom(?) of water

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Rate of Solution

• You are making a chicken broth using a bouillon
  cube. What are some things you can do to make it
  dissolve faster?
• Crush it
• Use hot water (increase temperature)
• Stir it

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Learning Check SF6

• You need to dissolve some gelatin in water.
  Indicate the effect of each of the following on
  the rate at which the gelatin dissolves as (1)
  increase, (2) decrease,
• (3) no change
• A. ___Heating the water
• B. ___Using large pieces of gelatin
• C. ___Stirring the solution

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Learning Check SF6

• You need to dissolve some gelatin in water.
  Indicate the effect of each of the following on
  the rate at which the gelatin dissolves as (1)
  increase, (2) decrease,
• (3) no change
• A. 1 Heating the water
• B. 2 Using large pieces of gelatin
• C. 2 Stirring the solution