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Understanding Solutions and Mixtures in Science

Explore the concepts of solutions, solutes, and solvents in homogenous mixtures. Learn about types of solutions, rates of dissolving, concentrations, solubility, and solution energy in this educational chapter. Partner activities and individual assessments included.

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Understanding Solutions and Mixtures in Science

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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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