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Properties of Water

Properties of Water. Water is polar: Oxygen is more electronegative than Hydrogen. Creates partial (+) charges at the hydrogen atoms & a partial (-) charge at the oxygen atom. Hydrogen bonds form between water molecules.

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Properties of Water

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  1. Properties of Water • Water is polar: • Oxygen is more electronegative than Hydrogen. • Creates partial (+) charges at the hydrogen atoms & a partial (-) charge at the oxygen atom. • Hydrogen bonds form between water molecules. • The partial (+) end of one water molecule is attracted to the partially (-) end of another water molecule. • Hydrogen bonds are weak!

  2. (+) (+) (+) (+) (+) (+) + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + (-) (-) (-) (-) (-) (-) Hydrogen Bonding

  3. Properties of Water • Water’s polarity and hydrogen bonding cause: • Capillary Action • High Surface Tension • High Specific Heat • Solubility • Density • High freezing and boiling points • Low vapor pressure

  4. Capillary Action • Capillary Action • Water molecules are able to channel themselves in and through small openings. • Allows water (and its dissolved substances) to move through the roots of plants and through the tiny blood vessels in our bodies. • Causes the meniscus.

  5. Surface Tension • Surface Tension is the inward force that minimizes the surface area of a liquid. • Cohesion (sticking) between the water molecules is caused by hydrogen bonding. • Causes water droplets/beads. • Allows the water strider to “walk” on water.

  6. Density of Water • The density of ice is less than water. • When frozen, the hydrogen bonds arrange the water molecules into an open honeycomb shape.

  7. Density • What property of water causes the occurrence in the picture below?

  8. Capillary Action • What property of water causes the occurrence in the picture below?

  9. Polarity • What property of water causes the occurrence in the picture below?

  10. Solutions • A solution is a mixture of two or more substances that are evenly distributed at the molecular level. • Coffee is a solution. What’s in it? • Can we see all the parts?

  11. 2 Parts to All Solutions • Solvent – The part of the mixture present in the greatest amount (part doing the dissolving). • Solute – The part or parts of the mixture present in the lesser amount (part being dissolved). • “Like Dissolves Like” • Polar substances dissolve in other polar substances. • Non-polar substances dissolve in other non-polar substances.

  12. Properties of Solutions • Miscible – liquids that can dissolve in each other. • EX: water/alcohol • Immiscible – liquids that can’t dissolve in each other. • EX: water/oil

  13. Aqueous Solutions • Electrolyte – a substance that conducts an electrical current in aqueous solution. • Weak electrolyte – only part of the substance dissolves, therefore only a weak electrical current can be carried • Strong electrolyte – almost all dissolves, therefore strong current. • Non-electrolyte – a substance that doesn’t conduct electrical currents

  14. Strong Electrolyte Solution Weak Electrolyte Solution

  15. Solvation • Solvation is the process of dissolving. solute particles are surrounded by solvent particles First... solute particles are separated and pulled into solution Then...

  16. Solubility • Solubility – the maximum amount of solute that can be dissolved in a given solvent at a given temperature.

  17. Types of Solutions • Saturated solution – a solution that contains the maximum amount of solute…no more solute will dissolve • Ex: tea with a lot of sugar but not so much to where it falls to the bottom • Unsaturated solution – more solute can dissolve. • Ex: tea with not enough sugar

  18. Types of Solutions • Supersaturated Solutions – a solution that contains more dissolved solute than is theoretically possible. Usually created by heating the solution and then slowly cooling it back down.

  19. Solutions with Solids • Factors that affect the rate of solvation of solids: • Agitation increases rate of dissolving by bringing more fresh solvent into contact with the solute. • Increasing temperature increases rate of dissolving • Decreasing particle size increases rate of dissolving by allowing fresh more solvent to come into contact with more of the solute • Why? Because solvation only occurs at the surface. All of these increase the amount of solvent contacting the surface.

  20. Solutions with Gases • Factors that affect solutions with gases: • Temperature • Most gases decrease in solubility with an increase in temperature. • Pressure • The solubility of a gas increase with increased pressure. • EX: soft drinks

  21. Solubility Curves • A solubility curve shows the dependence of solubility on temperature.

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