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Unit 3: Matter & Mixtures

Unit 3: Matter & Mixtures. Slide Show #5: Concentration & Solubility. Solubility Terms (Review) Section 8.1, p.254-258. In slide show #4, we learned the following terms: Solution Solute Solvent Dissolving Soluble Mechanical mixture Insoluble.

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Unit 3: Matter & Mixtures

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  1. Unit 3: Matter & Mixtures Slide Show #5: Concentration & Solubility

  2. Solubility Terms (Review)Section 8.1, p.254-258 • In slide show #4, we learned the following terms: • Solution • Solute • Solvent • Dissolving • Soluble • Mechanical mixture • Insoluble

  3. Solubility Terms (Review)Section 8.1, p.254-258 • In the space below, use ALL the terms on the previous slide in a paragraph to show their meaning. • Share your paragraph with the class or partner.

  4. To Dissolve or Not to DissolveSection 8.1, p.254-258 (Review) • Why does salt dissolve in water while pepper does not? • From slide show #4, we learned that salt particles are attracted to the water particles. This causes the salt particles to intermingle producing a solution (homogeneous mixture). • Scientifically, when the solute particles are more attracted to the solvent particles than they are to themselves, a solution is made. • Pepper, on the other hand, is more attracted to themselves than to the water, so they remain clumped together forming a mechanical mixture (heterogeneous).

  5. Review QuestionsSection 8.1, p.254-258 • Complete the following questions as review: • Page 261: #1, 2, 3, 4, & 7 • These are to be done at home and will be checked!

  6. ConcentrationSection 8.2, p.262-263 • Read pages 262 and 263. • What is a concentrated solution? • A concentrated solution is • What is a dilute solution? • A dilute solution is

  7. ConcentrationSection 8.2, p.262-263 • In the table below, given examples of solutions that would be considered concentrated or dilute:

  8. ConcentrationSection 8.2, p.262-263 • What does the term concentration mean? • Concentration refers to the amount of solute dissolved in a certain amount of solvent. • Concentration can be expressed in two ways: • In words – qualitatively • With numbers - quantitatively

  9. Concentration - QualitativeSection 8.2, p.262-263 • When you describe the concentration of a mixture qualitatively, you often use the words dilute or concentrated. • Ex: My glass of lemonade tastes very strong. It is too concentrated. • Ex: My glass of Kool-Aid tastes watery. It is too dilute.

  10. Concentration - QualitativeSection 8.2, p.262-263 • A key indicator for identifying and describing solutions qualitatively as dilute or concentrated is color. • As you can see from the picture below, the higher the concentration, the darker the color.

  11. Concentration - QuantitativeSection 8.2, p.262-263 • When you describe the concentration of a mixture quantitatively, you must determine the concentration mathematically using numbers. • You may already be familiar with the word quantity which means amount. • The quantitative concentration is commonly given as g/L (grams/liter). This tells you the mass of the solute in grams for every liter of solution.

  12. Concentration - QuantitativeSection 8.2, p.262-263 • Examples: • A) Josh mixed 120mg of hot chocolate into one liter of hot water. • Concentration = 120 mg/L • B) Alexis mixed 30 g of salt in 2 liters of water. • Concentration = 30g/2L = 15 g/L • What was done mathematically here?

  13. Concentration - QuantitativeSection 8.2, p.262-263 • Sometimes it is necessary to set up equivalent fractions before you can determine the concentration. • Example: Mrs. Stewart put 10g of sugar in her cup of coffee (250 mL). What is the concentration? • In this case, it is easier to convert liters to milliliters: 1L = 1000mL.

  14. Concentration - QuantitativeSection 8.2, p.262-263 • Example 2: Ms. Stanley added 15g of coffee to 500 mL of water. What is the concentration? • We’ll do this one together on the board:

  15. Concentration - QuantitativeSection 8.2, p.262-263 • You try these! • Hilary added 24 mg of Kool-Aid to 2 liters of water. • Matthew mixed 12 g of salt in 3000 mL of water. • Katie added 15 mg of sugar to 2 cups of tea.(1cup = 250mL)

  16. A Limit to ConcentrationSection 8.2, p.264 • Read “A Limit to Concentration” on p.264. • You all have most likely experienced a time when you could not dissolve all the Kool-Aid or hot chocolate that you added to your water or milk! • When a solution can no longer dissolve any more solute, it is said to be saturated. Until this point is reached, the solution is unsaturated.

  17. A Limit to ConcentrationSection 8.2, p.264

  18. SolubilitySection 8.2, p.264 • Read “Solubility” on p.264. • We have already learned that a salt is soluble in water since it dissolves. • Solubility refers to the amount of solute (salt) that can dissolve in a certain amount of solvent (water) at a given temperature. • Your text says that the solubility of salt in water at 0oC is 357 g/L. This means that for every liter of water, 357 g of salt can dissolve. • What would happen if you tried to dissolve 400 g of salt?

  19. SolubilitySection 8.2, p.264 • The following solutes were mixed into a liter of water at 0oC. Using the table given on page 264, classify the solutions as saturated or unsaturated.

  20. Rate of DissolvingSection 8.2, p.265-266 • Read pages 265-266. • Rate of dissolvingrefers to how fast something will dissolve. • Your text discusses 2 factors that effect rate of dissolving: • Stirring • Size of solute

  21. Rate of DissolvingSection 8.2, p.265-266 • Stirring • When you stir a mixture, you cause the solute particles to interact with the solvent particles more quickly. • As a result, the rate of dissolving increases. • Check out this animation! • Stirring, however, does NOT affect the solubility of a substance. • You can try to stir pepper in water as long as you want, but you will not be successful!

  22. Rate of DissolvingSection 8.2, p.265-266 • Size of Solute (p.266) • When you put a sugar cube into a glass of water, the outside of the sugar cube dissolves first. • Breaking up the sugar cube exposes more of the sugar (see Fig.8.12, p.266). • Since there is more interaction between the sugar particles and the water particles, it dissolves faster. That is, the rate of dissolving increases. • Does the size affect the solubility?

  23. Factors of SolubilitySection 8.2, p.267-271 • Read pages 267-271. • Both stirring and the size of the solute do NOT effect the solubility of a substance. • That is, the amount of solute that dissolves will not change when these factors change. Only the speed of dissolving changes. • Your text, however, discusses 2 factors that do effect the solubility: • Pressure • Temperature

  24. Factors of SolubilitySection 8.2, p.265-271 • Pressure (p.267) • When liquids are under pressure, more gas can dissolve in the liquid. • This is because the pressure forces the gas particles in the spaces between the liquid particles. • When this pressure is released, the gas comes out of the solution. This explains the “fizz” from a pop when it opens or a diver getting “the bends” if they rise too quickly from a large depth.

  25. Factors of SolubilitySection 8.2, p.265-271

  26. Factors of SolubilitySection 8.2, p.265-271 • Temperature • The temperature of the solvent has a great impact on the solubility of a solute. We will now complete a lab to determine this relationship! • Lab 8-2A: “How Does Temperature Affect Solubility?”, p.268 – 269.

  27. Chapter 8 Reviewp.274-275 • Assignment: • #2,3,5,6,7,9,10,11,12, p.274-275

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