1. Solubility and the Rate of Dissolving

2. In order to understand solutions, you have to understand 2 words: Solute: ________________________________ Solvent: ________________________________ water salt saltwater solution The substance doing the dissolving The substance being dissolved solute solvent

3. Water is a great solvent because of the arrangement of its molecules. This causes the electrons to be shared unevenly making it very POLAR. Why is water such a great solvent? Which side of water is positive, and which side is negative? What about water never changes? The ratio of hydrogen to oxygen.

4. Dissolving Dissolving is a ________ change. When substances dissolve, they simply break apart into their smallest units. These are too tiny to see, so it often looks like they disappear. physical When ionic compounds dissolve, they break apart into their ions.

5. As the temperature increases, the solubility of a solid increases. How are temperature and the solubility of a solid related? As the temperature decreases, the solubility of a solid decreases.

6. As the temperature increases, the solubility of a gas decreases. How are temperature and the solubility of a gas related? As the temperature decreases, the solubility of a gas increases. This means that as the temperature goes up, LESS solute can be dissolved.

7. Notice that in regards to temperature, solids and gases are opposites.

8. How are pressure and the solubility of a solid related? Mercury column used to measure pressure. Photo by Hans Grober As the pressure increases, the solubility of a solid is not affected. As the pressure decreases, the solubility of a solid is not affected. This means that the pressure going up and down has no effect on how much SOLID solute can be dissolved.

9. As the pressure increases, the solubility of a gas increases. How are pressure and the solubility of a gas related? As the pressure decreases, the solubility of a gas decreases. This means that as the pressure goes up, more gaseous solute can be dissolved.

10. Notice that in regards to pressure, solids and gases are NOT opposites. Pressure has no affect on solids! Pressure still has no affect on solids!

11. It is also important to understand what will affect the rate of dissolving of a solid. The rate of dissolving just means how fast a solute will dissolve.

12. How are temperature and the rate of dissolving of a solid related? Adding heat (thermal energy) will make solid solutes dissolve faster. Cooling down solutions will make solid solutes dissolve more slowly

13. How are stirring and the rate of dissolving of a solid related? Stirring a solution will make a solid solute dissolve faster. Stirring a solution will not force more solute to be dissolved. It will only make solute dissolve more quickly into an unsaturated solution. Glass stir rods are used to stir solutions in the lab.

14. How are the size of particles and the rate of dissolving of a solid related? Smaller crystal dissolve more quickly than larger crystals. Larger crystals dissolve more slowly. Large crystals can be crushed using an instrument known as a mortar and pestle.

15. How are the size of particles and the rate of dissolving of a solid related? After a heart attack, it can be beneficial to give the victim a dose of aspirin to reduce their blood pressure and ease the load of the heart. (Assuming they are not allergic.) Would it be better to give them a tablet of aspirin or a powdered aspirin? The powdered tablet would dissolve faster in the stomach and reduce the blood pressure more quickly!

16. Measuring Pressure Since the prefix bar- means pressure, pressure is measured with a barometer.

17. Applications of Pressure and Gases Carbonated water is a supersaturated solution. How is the supersaturated solution created? By adding the CO 2 to the water under very high pressure. What specific gas is dissolved in water to carbonate it? Carbon Dioxide (CO 2 )

18. Applications of Pressure and Gases According the graph, what will happen to the solubility of gases such as nitrogen as the scuba diver swims deeper into the ocean. What will happen to the dissolved gases as the diver returns to the surface? The gas will come out of the blood to be breathed back out. The solubility of the gases will increase.

19. Tiny alveoli fill your lungs and transfer gases between the lungs and the blood. What will happen to these alveoli when they are placed under too much pressure? They will POP!

20. While decompression sickness, often called “The Bends”, can be fatal, it is treatable if caught early enough. Patients are often placed in a hyperbaric chamber. This increases the pressure of oxygen making it easier for the patient to breathe. Hyper means above Bar means pressure Hyperbaric means above the normal pressure.

21. Applications of Temperature and Gases Why do power plants and factories use water as a coolant? Would gases be more or less soluble in this hot water? Gases are LESS soluble in hot water. The number of dissolved gases would decrease as the water became hotter and hotter. Because it has such a high specific heat!

22. The loss of which gas has the greatest impact when water is overheated? Is removing gases from the water a physical or a chemical change? This is a physical change. Solubility is a physical property. Oxygen Gas (O 2 ) Without enough oxygen, plants and animals begin to die. What is this type of pollution called? Thermal Pollution

23. Which of the following affects would be expected if the change to the solute on the left were applied?

24. Which of the following affects would be expected if the change to the SOLID solute on the left were applied?