Presentation on theme: "Primarily due to polarity"— Presentation transcript:
1Primarily due to polarity Properties of WaterPrimarily due to polarity
2Video1 “Properties of water” – 4 ½ min Why is ice less dense than water?How does ice floating on water impact the survival of the living organismsDraw the water structure.How does the term “polar” describe the water molecule?What is the intermolecular force between water molecules called?Explain surface tension in water
3Intro to water Molecule two hydrogen atoms and one oxygen atom v-shaped triangular moleculehydrogen bondsPolarityproperties
4Intro to WaterWater is a molecule made up of two hydrogen atoms and one oxygen atom. It has the formula H2O. When oxygen and hydrogen combine (H-O-H) they form a v-shaped triangular molecule. While water molecules are electrically neutral, the oxygen atom holds a small negative charge and the two hydrogen atoms hold small positive charges. Water molecules are attracted to each other, creating hydrogen bonds. These bonds determine almost every physical property of water and many of its chemical properties too. Scientists believe this unusual electrical balancing, called polarity, gives water some of its remarkable properties
5Terms to know by the end of the lesson Video 2 PolarityHydrogen bondCohesionAdhesionSurface tensionCapillary actionSpecific heat
6Water Physical Properties (review) At what temperature in Celsius does water start boiling?At what temperature in Celsius does water start melting?At what temperature in Celsius does water start freezing?What is the density of water?
7Water has a high specific heat capacity Water has the ability to absorb a lot of heat with a relatively small increase in temperatureWater has one of the highest specific heat capacityThis allows marine organisms to avoid drastic temperature fluctuations in the seawater.This allows orchards grown on the coast to survive hot summers and severe winters.
11Thinking criticallyVideos5&6If matter expands when heated, and contracts when cooled, why does ice expand (increase in volume) when water freezes?
12When water freezes, it goes from a mixed up liquid state where all these V's are just sliding around each other, to an ordered crystalline solid state where all the V's have to connect with each other in nice orderly solid shapes.
13The closest and easiest solid crystal shape for something that exists as a degree V is a hexagonal (really tetrahedral in 3D) crystal. Think of it as a flat hexagonal snowflake shape, but it really goes in three dimensions. The water molecules want to do this because to them it "feels" nicer--that is: they feel less strain and they can get into a lower energy state by getting into this nice orderly hexagonal crystal.
14video clip “Why ice float “ Critical Thinking: If ice were more dense than liquid water, how would this impact the survival of the marine life? (The floating layer of ice insulates the liquid water below, so that it wouldn’t freeze – this makes the ocean environment to easier to live in)
16H2O is Polar As we know – water is neutral (equal number of e- & p+ = zero Net Charge)But because the O atom is more electronegative than the H atoms – electrons spend more of their time nearer the oxygen. (O atom attracts more than its “fair” share” of electrons).This gives water a slight overall charge.The oxygen end “acts” negative.The hydrogen end “acts” positive.This charge is called polarity
17Oxygen “pulls” closer to it creating positive and negative sides of the polar molecule.
20Blast from the past: What is electronegativity? How does it change across a period?Down a group?What is the most electronegative element on the PT?Least electronegative?Which of the two elements, S or N, has a greater ability to attract another atom’s valence electrons?
22I am more electronegative than selenium, but less electronegative than chlorine? Who am I?
23Electronegativity values-how to determine if a bond is polar or not-polar Oxygen – 3.44 Hydrogen – 2.20 Difference in values– 1.24 (polar bond) The bond is polar if the difference is between Non-polar = or less than 0.5 Ionic = or greater than 1.7
24Other examples of polar molecules (no lone pairs): Carbon is more electronegativeOxygen is more electronegative
26Water is a universal solvent Water can dissolve more substances than any other solvent.Give examples of substances that water can dissolve.The dissolving power of water is very important for life on Earth. Wherever water goes, it carries dissolved chemicals, minerals, and nutrients that are used to support living things.Water is a universal solvent
28“Like dissolves like” (due to its polarity) Water (polar) + Styrofoam (non-polar)Acetone (nonpolar) + Styrofoam (non-polar)“Like dissolves like” (due to its polarity)
29Polar Bonding Polarity really does allow bonding They are hydrogen bonds and they are weakThey last for fractions of a secondContinuously break and reformvideo clip “Water molecule Part 1” - bonds breaking and reformingPolar Bonding
30Hydrogen Bonds (Formed between a highly Electronegative atom of a polar molecule and a hydrogen (O-H)Opposites attract
31This model to show the attraction between H and O – hydrogen bonding
33Cohesion (water is sticky) Attraction between particles of the same substance ( why water is attracted to itself)Results in Surface tension (a measure of the strength of water’s surface)Produces a surface film on water that allows insects to walk on the surface of water
34Inside a drop of water polar water molecules attract to each other in a random fashion At the surface of the drop, water does not attract to the airA unified layer of molecules at the surface creates surface tensionThere the water behaves like an flexible sheet allowing denser objects to “sit” on the surface.Surface Tension
35Surface tension (cohesion) Can be seen as waterdroplets formHelps insects walk acrosswaterSurface tension (cohesion)
36Adhesion Attraction between two different substances. Water will form hydrogen bonds with other surfaces such as glass, soil, plant tissues, and cottonAdhesion Causes Capillary Action, which gives water the ability to “climb” structures.
37Adhesion Form spheres & hold onto plant leaves Can be seen as water droplets form on the spider web (another polar surface)Form spheres & hold onto plant leavesAdhesion
38Capillary actionWe know that gravity is ALWAYS pulling on objects with massYet water can move up a paper towel with relative ease – How can this happen?Because the positive and negative charges in the paper attract the polar water molecules (adhesion)This property of adhesion is called capillary action.
39Warm up: 2/25/13Explain the following water properties in both words and drawings(2 min)Polarity-Like dissolves like-Heat capacityWater acts as a magnet-Trade notebooks with your partner write one constructive comment in your partner’s notebook. Hand them back their notebook( 1min)
40How do heterogeneous and homogeneous mixtures differ?(Left Side) Salt solution and Oil in water2 min - Quick Write: Based on your prior knowledge about mixtures, explain why a salt solution is classified as a homogeneous mixture and a mixture of oil and water is said to be a heterogeneous mixture.White boards activity:Homo- or Hetero - ?COKEAIRSTEELA JAR OF PENNIESCoke (mixture of CO2 gas, water, sugar, caramel color, food flavorings)Air (mixture of O2 and N2)Steel (alloy – mixture of Fe and C)A jar of pennies and nickelsNotes
41By the end of the day you will know: SoluteSolventSolutionSolubleInsolubleImmiscibleSeparationSolvationFactors affecting the rate of dissolutionNext notes…
42Complete the sentences. When you put salt into water it______. The salt dissolves because it is ________in the water. The substance which dissolves is called the ______. The substance that does the dissolving is called the _______. When something dissolves you get a _______.Water is a ________. Salt is a ________.When a substance does not dissolve it is________Dissolution of salt in waterwater.jsp
43Animation - Dissolution of an Ionic compound (results in dissociation) and a covalent compound (no dissociation)wfAnimation – Strong electrolyte (complete dissociation into ions) – many ionic compounds – conduct electricity - (+ strong acids and bases – will cover in more detail in Bundle 11)Animation – Weak electrolyte (partial dissociation) – weak acids and bases (if a conductivity meter is used - light is not as bright (dim) compared to a strong electrolyte)Animation – Non-electrolyte ( no dissociation) - no disruption of its molecular (covalent) structure – does not conduct electricity
44Checking for understanding The dissolved components of ionic and covalent compounds are:All ionsIons for ionic and molecules for covalent compoundsIons for covalent and molecules for ionic
45The dissolution of KNO3 and C3H6O (acetone) in water occurs: Molecules by molecules for both KNO3 and C3H6OIon by ion for KNO3 and molecule by molecule for C3H6OIon by ion for C3H6O and molecule by molecule for KNO3
46Based on your observations of the dissolution process on the animation, how do you think substances get dissolved?Each solvent molecules gets separated from other molecules and is surrounded by ions in ionic substances or molecules in covalent substancesEach ion in covalent substances and each molecule in ionic substances gets separated from other molecules or ions and is surrounded by solvent moleculesEach ion in ionic substances and each molecule in covalent substances gets separated from other molecules or ions and is surrounded by solvent molecules.
47For the following reaction Warm up 2/25/13For the following reactionidentify the products as insoluble or soluble.Na2CO3 + CaCl2 CaCO3 + 2NaClClassify the type of reactionActivitySketch the process of dissolution of calcium chloride. Find a partner - compare each other’s drawings – make corrections if needed(4min)
48Factors that Affect the Rate of Dissolution Pre-assessment:If you wanted to dissolve a substance in water as quickly as possible what could you do?
49The three methods to increase the rate of dissolving for a solid are? Heat it!Crush it!Stir it!
50How can you achieve the following: Increased number of collisions between solvent and soluteAgitationIncreased surface areaIncreased kinetic energy
51Notes –Solubilitythe amount of solute that will dissolve in a given amount of solvent at a specified temperature and pressure (for gases)grams of solute per grams of solventgrams of solute per 100ml of solvent
52Example: at 25. 0 0C, the solubility of sodium chloride is 35 Example: at C, the solubility of sodium chloride is 35.0 grams per 100 ml of water.You can dissolve up to 35.0 grams of sodium chloride in 100 ml of water.If you add more than 35.0 grams the solid will simply not dissolve.
53Based on solubility we can have three types of solutions: Unsaturated – a solution that could dissolve MORE solute at a specific temperature Saturated – a solution that contains the MAX amount of solute that can dissolve at a specific temp (stable)Visual evidence: a small quantity of un-dissolved solute remains in solutionSupersaturated – a solution that contains more dissolved solute than a saturated solution. (Prepared by heating the solvent, adding solute, and cooling slowly – very unstable)DEMO. Supersaturated solution of Sodium Acetate
54Solubility Graph Grams of solute per 100 g of water NaClO3 KBr NaCl Grams solute/100 g H2ONaClO3KNO3KBrNaClTemperatureSolubility GraphGrams of solute per 100 g of water
55How much solute will dissolve? A solubility curve shows the amount of each solute that will dissolve in 100g H20 at each temperature.Saturated is on the line.Unsaturated is below the line.Supersaturated is above the line.Grams solute/100 g H2ONaClO3KNO3KBrNaClTemperature
56How much solute will dissolve? A solubility curve shows the amount of each solute that will dissolve in 100g H20 at each temperature.Saturated is on the line.Unsaturated is below the line.Supersaturated is above the line.SaturatedGrams solute/100 g H2O
57What is the solubility of KNO3 at 60 oC in 200 g of H2O? How many grams of KBr can dissolve in 300 gr of H2O at 100 oC?Grams solute/100 g H2ONaClO3KNO3KBrNaClTemperature
58How much solute will dissolve? Grams solute/100 g H2OUnsaturated
59How much NaClO3 would you have to add to 100 g of water at 50oC to make a saturated solution? Look at the intersection.Grams solute/100 g H2OApprox. 140 – 142 g
60Mini Lab: WHAT FACTORS INFLUENCE DISSOLUTION Surface Area (Solid Solute)1) Record the time 1 sugar cube needs to dissolve in 200 ml of tap water. ______2) Crush 1 sugar cube in the mortar & pestle. Record the time the crushed sugar cube needs to dissolve in 200 ml of tap water. _____________Temperature (Solid Solute)3) Obtain 200 ml of warm water from the front lab table. Color one side of the sugar cube with a Vis-A-Vis marker. Add the sugar cube to the warm water & record the time the cube needs to dissolve. _____________ 4) Obtain 200 ml of cold water from the front lab table. Color one side of the sugar cube with a Vis-A-Vis marker. Add the sugar cube to the cold water & record the time the cube needs to dissolve.___________Stirring (Solid Solute)5) Place 1 sugar cube in 200 ml of tap water. Record the time the cube needs to dissolve without stirring.______________6) Place 1 sugar cube in 200 ml of tap water. Record the time the cube needs to dissolve while you stir the solution._____________
61Homework: Lab analysis questions 1) How do you increase the surface area of a solid?2) How is surface area of a solid solute related to dissolution? WHY?3) How is temperature related to the dissolution of a solid solute? WHY?4) What effect does stirring have on the dissolution of a solid solute? WHY?
63The Great Soda Mystery!What is the difference between the hot soda and cold soda? Why?As temperature _______,solubility of a gas ______.3. Does pressure affect the amount of gas in the soda? How?4. As pressure _____, solubility of gases ______.
64In general solubility of solids increases with increasing temperature. Temperature EffectsIn general solubility of solids increases with increasing temperature.Solubility of gases in water decreases with increasing temperature.Thermal Pollution: of lakes and streams leads to a decrease in oxygen content of the water.Warmer waters is less dense and is found at the surface where the oxygen must dissolve to reach water at lower depths.
65Solubility of GasesWhen something is heated it will favor the gas phase, therefore, heating solutions with gaseous solutes will decrease the solubility.For example, carbonated water can dissolve more carbon dioxide at lower temperatures. The following is a solubility curve for gases
67PressurePressure has little effect on the solubility of liquids or solids in liquid solvents.(can’t not be compressed)The solubility of a gas in a liquid solvent INCREASES when pressure increases. The pressure holds the solute (CO2 gas) in the solution.
68Electrolyte - An ionic compoud whose aqueous solution conducts electricity. (Dissolved in water, the positive and negative ions are free to move (mobile ions) and can conduct elect.)Solid ionic compounds can’t conduct electricity (ions are present but they are NOT mobile)Strong (HCl, KCl) – completely ionize in water.Weak (vinegar – acetic acid) – partially ionize in waterEx: NaCl almost completely ionizes in solution and produces positive and negative ions, which will conduct electricity. Electrolytes can be found in sports drinks (ex. Gatorade) – maintain homeostasis.
69Warm up 3/5/13 1) When the attractive forces within the particles of a solid substance are weaker than the attractive forces between the solid particles and its liquid solvent, what will happen to the solid substance? Draw a picture representing the above scenario.
70Exit Pass- What do all of the following have in common? KCl(aq) NaCl(aq) AgNO3(aq)NaOH(aq) HCl(aq)They are all homogeneous mixtures= solutionsWhich is the solute and solvent in each one?
71Concentration of Solutions How would you describe the concentration of the Kool-Aid solutions? How do you know which solution contains more or less solute?
72Concentration – a measure of how much solute is dissolved in a specific amount of solvent. Concentration may be described qualitatively using the words:1. Concentrated- contains a LARGE amount of solute2. Dilute – contains a SMALL amount of solute
73Although qualitative descriptions of concentration can be useful, solutions are more often described quantitatively. One of the commonly used quantitative descriptions is MOLARITY.B. Calculating Concentration1. Molarity (M) – The # of moles of SOLUTE dissolved per LITER of solution.M = moles soluteL of solutiona. Ex: An IV solution contains 5.10 g of glucose (C6H12O6) in ml of solution. What is the molarity of the solution?b. Ex: How many grams of Na2SO4 would be dissolved in 1.5L of a .24M solution of Na2SO4?
74In the laboratory, you may use concentrated solutions of standard molarities called stock solutions. For example, concentrated hydrochloric acid (HCl) is 12M. You would rarely use this concentration in a lab. How would you prepare a LESS CONCENTRATED (dilute) solution? You can prepare a less concentrated solution by taking a concentrated solution (stock solution) and diluting it with solvent