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Chapter 21- SOLUTIONS

Chapter 21- SOLUTIONS. Sections 1 & 2. Pre-assessment. Work with your shoulder partner to answer the questions on pages 255-256 in your workbook. What is a solution?. Solutions are homogenous mixtures of substances They have the same composition throughout the solution

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Chapter 21- SOLUTIONS

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  1. Chapter 21- SOLUTIONS Sections 1 & 2

  2. Pre-assessment • Work with your shoulder partner to answer the questions on pages 255-256 in your workbook

  3. What is a solution? • Solutions are homogenous mixtures of substances • They have the same composition throughout the solution • Composed of a solute and a solvent

  4. Solutes vs Solvents • A solute is a substance that is dissolved in a solution by a solvent • A solvent is a substance that dissolves another substance in a solution • Work with your face partner to come up with some examples of solvents and solutes

  5. Types of solutions • Nonliquid • Gasses • Metals • Alloys • Liquid

  6. How do substances dissolve? • Solid into liquid- works best with two polar substances • Liquid molecules pull solid molecules away from main solid • Sugar cube in water • Liquids and gasses or gasses and gasses • Particles move to reach a state of equilibrium or become evenly spread throughout the mixture • Solids and solids • Both must first be melted • Then they are mixed while still molten • As the mixture cools the metals will remain mixed as they form a solid

  7. Rate of dissolving • Stirring- • Stirring a mixture increases the rate of dissolving by moving the solvent around the solute • This causes an increase in contact between the solvent and solute in the solution • Surface Area- • Increasing the surface area increase the rate of dissolving • Increases the amount of contact between the solute and the solvent

  8. Rate of dissolving • Temperature- • Increasing the temperature of a solution also increases the rate of dissolving • The solvent has more contact with the solute • By combing the three ways to increase rate of dissolving, you are making the solute dissolve very rapidly in the solvent

  9. Assessment • Section Review # 4-7 • Wkbk pgs 257-258 • Work individually on both!

  10. Concentration • Amount of solute in a solvent • Described in two ways • % volume • Molarity (we will not cover this in physical science)

  11. Solubility • Maximum amount of solute that can be dissolved in a given amount of solvent • Comparisons can be made between different substances only if the following are true: • Same amount of solvent • Same temperature • Same pressure if a gas

  12. Types of solutions • Saturated • Unsaturated • Supersaturated • With your shoulder partner, come up with a working definition for each type of solution. • DO NOT USE YOUR BOOK!! • Make your best definition with your combined prior knowledge

  13. Saturated solutions • Has the maximum amount of solute the given amount of solvent can hold at a specific temperature • If the temperature is increased, the saturation level will increase • Solubility curves- allow you to quickly compare saturations at different temperatures with different substances

  14. Unsaturated Solutions • Does not have the maximum amount of solute dissolved in the solvent at a specific temperature • When temperature is increased on a saturated solution, the solution will become unsaturated unless more solute is added

  15. Super-saturated solutions • When a solution contains more solute than a saturated solution at the same temperature • VERY UNSTABLE!!! • ANY disturbance can cause the excess solute to form crystals until the solution is at the saturated level for the given temperture

  16. Solution energy • Exothermic solutions- release energy when they form • Hot packs • NaOH and H2O • Endothermic solutions- absorb energy when they form • Cold packs • With your face partner, come up with three examples of exothermic solutions and three endothermic solutions

  17. Gas solubility • Disturbing a solution containing a gas will cause the gas to be released from the solution • Pressure- • Increased pressure on the solution increases the amount of gas that can be dissolved • Releasing pressure on the solution causes the gas to be released from the solution • Temperature- • Lower temperatures allow more gas to be dissolved in a solution • Higher temperatures release gas in a solution

  18. Assessment • Section review • #10-14 • Do these INDIVIDUALLY

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