1. Chapter 5 Solutions

2. What would happen if you put sand in a test tube of water? The sand would fall to the bottom of the test tube and never dissolve in the water.

3. What would happen if you put salt into a test tube of water? The salt would fall to the bottom of the test tube but unlike the sand, the salt would dissolve and you would have a solution of salt water.

4. The salt is being dissolved into a solution. Sand does not dissolve in water. Salt and water together is a type of solution: a mixture in which the particles of one substance are evenly mixed with the particles of another substance

5. In salt water, sodium ions and chlorine ions are evenly mixed with the molecules of water. There are different types of solutions. Liquid solutions: formed when solids, liquids and gases dissolve in a liquid.

6. Examples Salt water: salt is a solid and water is a liquid. Soda: Carbon dioxide, which is a gas is dissolved in the soda, which is a liquid. Antifreeze is a liquid dissolved in water.

7. Other solutions are those where different substances are dissolved into solids and gases. Examples: Air is an example of a gas dissolved in a gas. Oxygen and other gases are dissolved into Nitrogen. Brass is an example of a solid in a solid. It is zinc in copper.

8. Did you know that tap water is a solution? Tap water sometimes has dissolved iron in it or even compounds made with calcium. IT can also have chlorine it in.

9. Did you know that the air that you breathe is a solution? Air is full of different gases. There is nitrogen (which makes up most of the air that you breathe), oxygen and other gases all mixed together.

10. As you learned before, a solution is made: When particles of one substance are evenly mixed with the molecules of another substance.

11. How is salt water made? You take water and put it into a beaker. You then add salt to the water You can stir the mixture to make the salt dissolve faster. Lets make a mixture of salt water!!

12. The part of the solution that dissolves is called the solute. The part of the solution that the solute dissolves in is called the solvent. The solvent is usually the part of the solution that is present in a greater amount.

13. Example: Salt water: salt is the solute and the water is the solvent. In air, nitrogen would be the solvent because there is more of it in the mixture. Oxygen and the other gases are considered the solutes.

14. In most solutions the solute usually disappears. When some solutes dissolve in a solvent they can also create a colored solution.

15. Examples Solute that disappears? Solute that produces a color: if you place a crystal of a compound called potassium permanganate into water and let it sit, the water will eventually turn to a pink color after it sits for a few minutes.

16. Some substances are more soluble, able to dissolve, than other substances. Solubility: the maximum amount of a substance that will dissolve in a given quantity of a solvent at a given temperature.

17. Example 38 g of table salt (sodium chloride) will dissolve in 100g of water at 20 degrees Celsius. If you add more than this, the extra salt that you add will not dissolve. It will sink to the bottom.

18. There are also many substances that will not dissolve in water. Examples: Marbles, Aluminum foil, plastic and many others. They are called insoluble. Example: When you pour water into a glass, does the glass dissolve….NO!!

19. Some substances will be soluble in some solvents but are insoluble in other solvents. Example: Sugar will dissolve in water but not in oil. Oil does not dissolve in water, It all depends on the chemical makeup of the solvent that will determine if a substance dissolves in it or not.

20. As you may have learned before, water molecules are polar. A polar molecule: a molecule in which one end has a positive charge and the other end has a negative charge. The charge is so small that you cannot call the bond a ionic bond, it is covalent.

21. What is water made up of? One oxygen atom and two hydrogen atoms. The atoms are covalently bonded together. Oxygen has a slight negative charge. The hydrogen atoms have a slight positive charge.

23. Water is sometimes called the universal solvent. It is called this because many types of substances dissolve in it. The electric charges that water has help to dissolve different substances. The charged ends of the water molecules help separate particles of a solute and spread them out throughout the water.

24. Example Sugar water: When we put the sugar cube in the water, the sugar began to dissolve. What was happening was the water molecules were pulling the sugar molecules to them because water has a slight charge. This separated the molecules of sugar so that the sugar molecules were evenly distributed through the water.

25. A molecular solution is formed when there are forces of attraction between the solvent and the solute. The attraction between the two is greater than the force of attraction between the atoms that make up a molecule.

26. Example The force between the water and a sugar molecule is greater than the force between the sugar molecules.

27. As you know ionic compounds are made up of charged particles. These particles are positive and negative. How are they held together? By a force of attraction between opposite charges.

28. Example of an ionic solution: Salt water: Sodium ions and the chloride ions are attracted to the charged ends of the water molecules which is polar.

29. So how can make a solute dissolve faster in a solvent? One way to make the solute dissolve faster would be to stir the solution. Stirring is going to help the crystals of a certain substance to come apart quicker. Another factor that can speed up the rate that a solid solute dissolves in a liquid solvent is temperature.

30. Example: If the temperature of water is higher then solid solutes will dissolve faster.

31. When you have a liquid solvent and a gaseous solute, the opposite happens. The higher the temperature the slower the gas will dissolve in the liquid. Example: When soda is made, it is made at a low temperature because otherwise the gases will not dissolve.

32. The surface area of the solute will also determine how long it will take it to dissolve. The smaller the surface area the faster it will dissolve. The larger the surface area, the slower it will dissolve. Example: a solid sugar cube will dissolve slower than a crushed sugar cube. This is because the surface area of the solid sugar cube is greater than the crushed one

33. When it comes to gases, the amount of pressure that is present will affect the rate of solubility. If the pressure increases, the faster the gas will dissolve. Example: Can of soda, I am will explain!

34. Polar solvents: Water Dissolve compounds that are polar and ionic compounds but will not dissolve solutes that are nonpolar such as oil and fat.

35. There are different concentrations that a solution might have. You may have heard the terms dilute and concentrated before. Well if you haven’t lets go over what they mean. Both represent how much of a solute and solvent are in a solution.

36. A dilute solution: a solution containing a small amount of solute compared with the amount of solvent present. These solutions are weak. A concentrated solution: a solution containing a large amount of solute compared with the amount of solvent present. These solutions are strong.

37. There are also solutions in which we call unsaturated and saturated solutions. An unsaturated solution: a solution containing less solute that it can hold at a given temperature. Example: Having one gram of salt dissolved in 100 mL of water at 20 degrees Celsius when you know that 38 grams can be dissolved at this temperature.

38. A saturated solution: a solution containing all the solute it can hold at a given temperature. Example: 38 grams of salt dissolved in 100 mL of water at 20 degrees Celsius.

39. There is also another kind of a solution called a supersaturated solution. A supersaturated solution: solution containing more solute than it can normally hold ata given temperature. Example: Had a saturated solution of salt water. Raise the temperature up to 50 degrees Celsius. You can now add more salt because it is at a higher temperature. Let the solution cool and now the water will be holding more salt then it can normally hold.