Solutions

1. Solutions

2. What is a solution? • A solutionis a mixture that has the same composition, color, density, and even taste throughout.

3. Solutes and Solvents • To describe a solution, you may say that one substance is dissolved in another. • The substance being dissolved is the solute, and the substance doing the dissolving is the solvent. • When a solid dissolves in a liquid, the solid is the solute and the liquid is the solvent.

4. Universal Solvent • Water is often referred to as the universal solvent because it can dissolve so many things. • However, not all substances dissolve in water. Some substances are non-polar and have no separate positive and negative areas. Due to this, they will not attract to polar molecules like water. • Ex: Oils, fats and lipids

5. Non-liquid Solutions • Solutions can also be gaseous or even solid. • All mixtures of gases are solutions. • Air is a solution of 78% nitrogen, 20% oxygen, and small amounts of other gases such as argon, carbon dioxide, and hydrogen.

6. Dissolving Liquids and Gases • When gases dissolve in gases or when liquids dissolve in liquids, this movement spreads solutes evenly throughout the solvent, resulting in a homogeneous solution.

7. Rate of Dissolving • Sometimes the rate at which a solute dissolves into a solvent is fast and other times slow. • There are several things you can do to speed up the rate of dissolvingstirring, reducing crystal size, and increasing temperature are three of the most effective techniques.

8. Stirring a solution speeds up dissolving because it brings more fresh solvent into contact with more solute. The fresh solvent attracts the particles of solute, causing the solid solute to dissolve faster. Stirring

9. Crystal Size • Another way to speed the dissolving of a solid in a liquid is to grind large crystals into smaller ones. • Large crystals dissolve in water slowly because the amount of surface area is limited. • Increasing the amount of surface area by creating smaller particles increases the rate of dissolving.

10. Temperature • Increasing the temperature of a solvent speeds up the movement of its particles. • This increase causes more solvent particles to bump into the solute. As a result, solute particles break loose and dissolve faster.

11. Controlling the Process • Each technique, stirring, crushing, and heating, is known to speed up the rate of dissolving by itself. However, when two or more techniques are combined, the rate of dissolving is even faster.

12. How much can dissolve? • If you continue adding sugar to lemonade, eventually the point is reached when no more sugar dissolves and the excess granules sink to the bottom of the glass. • Solubility is the maximum amount of a solute that can be dissolved in a given amount of solvent at a given temperature.

13. Concentration • A concentrated solution is one in which a large amount of solute is dissolved in the solvent. • A dilute solution is one that has a small amount of solute in the solvent.

14. Types of Solutions–Saturated • A saturated solution is a solution that contains all the solute it can hold at a given temperature.

15. Saturated Solutions • Generally, as the temperature of a liquid solvent increases, the amount of solid solute that can dissolve in it also increases. This table shows the amounts of a few solutes that can dissolve in 100 g of water at different temperatures, forming saturated solutions.

16. Solubility Curves • Each line on the graph is called a solubility curve for a particular substance. • You can use a solubility curve to figure out how much solute will dissolve at any temperature given on the graph.

17. How would you describe NaClO3 with a concentration of 80g/100g of water at 40 °C? ____________________ • With a concentration of 120g/100g water at 45 °C? _____________________ • With a concentration of 160g/100g water at 45 °C? _____________________ • Which salt is least affected by temperature? _____________________ • Which is most affected by temperature? _____________________ • How many grams of KBr will form a saturated solution in 100 g of water at 50 °C? _____________________

18. Unsaturated Solutions • An unsaturated solution is any solution that can dissolve more solute at a given temperature. • Each time a saturated solution is heated to a higher temperature, it becomes unsaturated.

19. Supersaturated Solutions • A supersaturated solution is one that contains more solute than a saturated solution at the same temperature. • Supersaturated solutions are unstable.

20. Solubility of Gases • Shaking or pouring a solution of a gas in a liquid causes gas to come out of the solution. • Agitating the solution exposes more gas molecules to the surface, where they escape from the liquid.

21. Pressure Effects • Increasing the pressure of a gas forces the gas to dissolve into a liquid. • Soft drinks are bottled under increased pressure. • When the pressure is released, the carbon dioxide bubbles out.

22. Temperature Effects • Another way to increase the amount of gas that dissolves in a liquid is to cool the liquid. • This is just the opposite of what you do to increase the speed at which most solids dissolve in a liquid.

23. Sum it up! • Solutes and Solvents make up a solution • Solutions are homogeneous mixtures and can be made of solids, liquids or gases. • Water is aka the Universal Solvent • There are 3 types of Solutions: Unsaturated, saturated and supersaturated • Solubility is the maximum amount of a solute that can be dissolved in a given amount of solvent at a given temperature. • Solubility Curves show how solutes can dissolve at different temperatures. • We can increase the rate of solubility by increasing temp, stirring, reducing solute size, and increasing pressure .

24. Solubility Review Questions 1 In which of the following will sugar be harder to dissolve? • Hot tea • Warm milk • Hot coffee • Iced tea

25. 2 The substance that dissolves the solute is called the • Solution • Solvent • Solid • Salt water

26. 3 Which form of matter usually increases its solubility as the temperature decreases? • Liquid • Gas • Solid • Ice

27. 4 No matter how hot you make the tea, you cannot dissolve any more sugar into the solution. This is an example of a ____ solution. • Solvent • Hot • Heterogeneous • Saturated

28. 5 Which of the following helps to increase the rate of solubility in a liquid solution? • Stirring • Increasing temperature • Reducing crystal size of solute • All of the above

29. Answers • D • B • B • D • D