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Topic 15: Solutions

Table of Contents. Topic 15: Solutions. 15.1: Solutions. Today, do the following 3 things: Take notes on the slides (or you can print them off from home later Make flashcards for words like this . ( 20 total – we will use them in class tomorrow)

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Topic 15: Solutions

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  1. Table of Contents Topic 15: Solutions 15.1: Solutions • Today, do the following 3 things: • Take notes on the slides (or you can print them off from home later • Make flashcards for words like this. (20 total – we will use them in class tomorrow) • Write and turn in the answers for any questions like this. • Extra time? Read ahead on slides, begin WebAssign, etc.

  2. MATTER This unit focuses on solutions Heterogeneous materials Homogenous materials Mixtures SAME Substances Homogeneous mixtures (Solutions) Heterogeneous mixtures Chemical change Physical change Elements Compounds Solute = Solvent = Aqueous = dissolved dissolver water is solvent

  3. Solutions: Basic Concepts Some Helpful Definitions soluble – the ability of a solute to dissolve. insoluble – a solute unable to dissolve. solute – substance that is being dissolved (may change phase, lesser amount) solvent – substance doing the dissolving (no phase change, greater amount) miscible – two liquids that are soluble in any proportion. (Alcohol in water) immiscible – two liquids that will separate when mixing is stopped. (Gasoline in water)

  4. More Helpful Definitions aqueous – when water is the solvent, the solution is called aqueous solvation –solvent particles clustering around a solute particle (dissolving) hydration – solvation where water is the solvent saturated – when additional solute will not enter solution, but remains as a solid, the solution is said to be saturated (can no longer dissolve) solubility – the amount of solute needed to form a saturated solution is the solubility of that solute

  5. Solutions: Basic Concepts Concentrated Versus Dilute • Quantitative Expression • 12. Dilute: relatively small amount of solute • 13.Concentrated: relatively large amount of solute

  6. Solutions: Basic Concepts Water: The Super Solvent • Water is a very versatile solvent - the universal solvent. • In order for a solute to dissolve in water, the polar water molecules attract the particles of the solute

  7. Solutions: Basic Concepts Water Dissolves Many Covalent Substances • Water is also is a good solvent for some covalent compounds. ex) sucrose, C12H22O11 (table sugar) • Because it does not dissolve everything, we must be able to predict what it will and will not dissolve

  8. Solutions: Basic Concepts Factors Affecting Solubility • Solute-Solvent Interactions • 14. “Like Dissolves Like” • Substances of similar polarities will dissolve • Different polarities will not mix • Polar dissolves polar • (or ionic/H-bonding) • Non-polar dissolves non-polar • Non polar will not dissolve polar • See http://mmecall.weebly.com/chemistry-a.html - scroll down to “Like Dissolves Like”

  9. Solutions: Basic Concepts 15. Dissociation: The process by which charged particles in an ionic solid break apart. • Example of shorthand for dissolving and dissociation:

  10. Solutions: Basic Concepts Unsaturated Versus Saturated • We must consider the maximum amount of solute a solution can hold 16. Unsaturated solution: a solution where the amount of solute dissolved is less than what could be dissolved 17. Saturated solution: holds the maximum amount of solute per amount of the solution

  11. Solutions: Basic Concepts The Solution Process • 18. Supersaturated Solutions: A solution that has more solute dissolved in it than should be allowed • Formed by dissolving a solute in a heated solvent • When the solvent cools, the solute remains in solution, even though it creates a solution more concentrated than should be allowed • Very unstable – it may suddenly release • Equilibrium can be recovered by adding a “seed” crystal to encourage precipitation

  12. Solutions: Basic Concepts The Solution Process • Supersaturated Solutions • Wanna see? • http://mmecall.weebly.com/chemistry-a.html scroll down to “Supersaturated Solutions”

  13. Solutions: Basic Concepts Factors That Affect Rate of Solvation • Increasing collisions increases rate of solvation • Why is this true?

  14. 19. Factors That Affect Rate of Solvation • To increase collisions… • Nature of the solute and solvent • Agitate the mixture. • Increase surface area of solute. • How do each of these effect collisions?

  15. Solutions: Basic Concepts Factors That Affect Solubility • 4. Temperature • In liquid solvents • ↑ temperature, ↑ solubility of solid solutes. Why? solid solutes

  16. Solutions: Basic Concepts Factors That Affect Solubility • 4. Temperature • In liquid solvents • ↑ temperature, ↓ solubility of gaseous solutes. Why? gaseous solutes

  17. Solutions: Basic Concepts Factors That Affect Solubility • Pressure affects only gaseous solutes. • 20. Henry’s Law: ↑ pressure = ↑ solubility • As the pressure of the gas increases, the rate at which gas molecules strike the surface of the solvent (entering the solution) increases. As a result, more gas solute enters the solution • So…why does pop respond as it does when you unscrew the lid from a bottle of Coke?

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