Solutions Properties of Water Solutions

Predict the % water in the following foods

88% water 94% water 85% water 86% water

Water in the Body water gainwater loss liquids1000 mLurine 1500 mL food 1200 mLperspiring 300 mL cells 300 mL exhaling 600 mL feces 100 mL Calculate the total water gain and water loss Total ______ mL _____ mL

Water Most common solvent A polar molecule O  - a hydrogen bond H  +

Hydrogen Bonds Attract Polar Water Molecules

Explore: Surface 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

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?

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

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

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

Types of Solutions air O 2 gas and N 2 gas gas/gas gaseosa CO 2 gas in water gas/liquid seawater NaCl in water solid/liquid brass copper and zinc solid/solid

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

Test yourself (1) element (2) compound (3) solution A. water123 B. sugar 123 C. salt water 123 D. air123 E. tea123

Answers (1) element (2) compound (3) solution A. water2 B. sugar 2 C. salt water 3 D. air3 E. tea3

Test yourself 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 H 2 O + 5 g KCl solute = 1) KCl 2) H 2 O solvent = 1) KCl 2) H 2 O

Answers A. brass: 20 g zinc + 50 g copper solute= 1) zinc solvent = 2) copper B. 100 g H 2 O + 5 g KCl solute = 1) KCl solvent = 2) H 2 O

Test yourself Identify the solute in each of the following solutions: A. 2 g sugar (1) mL water (2) B mL ethyl alcohol(1) and 30.0 mL of methyl alcohol (2) C mL water (1) and 1.50 g NaCl (2) D. Air: 200 mL O 2 (1) mL N 2 (2)

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

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 (C 6 H 14 ) is needed to dissolve non-polar solutes such as oil or grease.

Self test Which of the following solutes will dissolve in water? Why? 1) Na 2 SO 4 2) gasoline 3) I 2 4) HCl

Answer Which of the following solutes will dissolve in water? Why? 1) Na 2 SO 4 Yes, polar (ionic) 2) gasoline No, non-polar 3) I 2 No, nonpolar 4) HClYes, Polar

Formation of a Solution Cl - Na + Cl - Na + H2OH2O H2OH2O Cl - solute Dissolved solute Hydration

Writing An Equation for a Solution When NaCl(s) dissolves in water, the reaction can be written as H 2 O NaCl(s) Na + (aq) + Cl - (aq) solid separation of ions in water

Self test 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

Answer 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

Rate of Solution You are making a chicken stock using an oxo cube. What are some things you can do to make it dissolve faster? Crush it Use hot water (increase temperature) Stir it

Self test 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

Answer 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