Presentation on theme: "WATER AND AQUEOUS SOLUTIONS"— Presentation transcript:
1 WATER AND AQUEOUS SOLUTIONS CHAPTER 17WATER AND AQUEOUS SOLUTIONS
2 Objectives: 1. Describe the hydrogen bonding that occurs in water. 2. Explain the high surface tension and low vapor pressure of water in terms of hydrogen bonding.
3 Water and its properties Water molecule1. triatomic H2O2. O-H polar bondpolar molecule
4 a. an inward force that tends to minimize the surface area of a liquid Surface propertiessurface tensiona. an inward force that tends to minimize the surface area of a liquidb. Gives the spherical shapec. Gravity helps flatten the shape
5 a. Wetting agent (soap or detergent) d. higher the surface tension the more spherical shapeSurfactanta. Wetting agent (soap or detergent)b. Reduces surface tension (flattens shape)c. Soap interferes with hydrogen bonds
6 Vapor pressurea. Caused by molecules that escape the surface of the water and enter the gas phaseb. Hydrogen bonds hold molecules togetherescape is lowc. Gives water unusually low vapor pressure
7 Specific heat capacity a. The quantity of heat, in joules or calories, required to raise the temperature of 1 g of a substance 1 °Cb. Water’s = J/g°C(helps moderate daily air temp.)
8 Evaporation and Condensation 1. heat of vaporization (evaporation) a Evaporation and Condensation 1. heat of vaporization (evaporation) a. amount of energy needed to convert 1 g of a substance from a liquid to gas b. Water takes 2.26 kJ of energy to convert 1 g of liquid to 1 g of steam at 100 °C
9 c. Absorbs high amount of heat because of hydrogen bonds 2 c. Absorbs high amount of heat because of hydrogen bonds 2. heat of condensation a. Water needs 2.26 kJ of heat to turn from a gas to a liquid b. Opposite of evaporation
10 c. You get a worse burn from steam d c. You get a worse burn from steam d. Water has a high boiling point due to hydrogen bonds Ice 1. Expands as liquid turns to a solid 2. Density a. 4 °C water is most denses
11 b. Below 4 °C the density decreases c b. Below 4 °C the density decreases c. Lower density causes ice to float d. Why does water act differently? 1. shape
12 2. Molecules have empty space 3. 4 2. Molecules have empty space Ice melts at 0oC (happens at the same time as freezing) 5. Heat absorbed when changing from a solid to a liquid is 334 J/g 6. pond
13 Objectives: By the end of class you will be able to: 4. Explain the significance of the statement “like dissolves like.”5. Distinguish among strong electrolytes, weak electrolytes, and nonelectrolytes.
14 Aqueous Solutions1. Substances dissolved in water2. Two partsa. Solvent – the part that causes the dissolvingb. Solute – the part that dissolves
15 3. substances that dissolve in water readily are ionic and polar 4 3. substances that dissolve in water readily are ionic and polar 4. The Process Solvation a. The process that occurs when a solute dissolves
16 b. Water molecules are in constant motion c b. Water molecules are in constant motion c. The solvent (H2O) attract the solute (Na+1 Cl-1) d. e. Some ionic compounds are insoluble
17 5. Electrolytes a. Produce an electrical current in (aq) solutions b 5. Electrolytes a. Produce an electrical current in (aq) solutions b. Ionic compounds c. Some solids will when melted (molten state)
19 6. Nonelectrolytes Do not conduct an electric current 7 6.Nonelectrolytes Do not conduct an electric current 7. There are weak electrolytes and strong electrolytes (see page 485) weak electrolytes dissociate slightly
20 8. Water of hydration a. a crystal containing water b 8. Water of hydration a. a crystal containing water b. Called a hydrate c. formula CuSO4 5H2O
21 d. reaction CuSO4. 5H2O(s) CuSO4(s) + 5H2O(l) e. Effloresce 1 d. reaction CuSO4*5H2O(s) CuSO4(s) + 5H2O(l) e. Effloresce 1. hydrate losing water 2. Has a higher vapor pressure than water 3. becomes coated with white powder
22 f. hygroscopic 1. lower vapor pressure than water 2 f. hygroscopic 1. lower vapor pressure than water 2. Remove water from the air 3. Solids will become slightly wet
23 4. Used as drying agents g. desiccants remove lots of water from the air and form a solution
24 h. % water calculations percent H2O = mass of water X 100 mass of hydrate Calculate the percent by mass of water in washing soda, or sodium carbonate decahydrate (Na2CO3*10H2O).
25 Objectives: By the end of class you will be able to: 6. Explain how colloids and suspensions differ from solutions.7. Describe the Tyndall effect.
26 Heterogeneous Mixtures 1. Suspensionsa. Mixtures that settle outb. Muddy water, Italian dressing
27 2. Colloids a. Fall in between a suspension and solution b 2. Colloids a. Fall in between a suspension and solution b. Dispersed phase c. Gelatin, paint, smoke
28 d. appear cloudy or milky when concentrated e. look clear when dilute f. Tyndall effect - scattering of visible light in all directions
29 h. colloid particles also absorb ions g. colloid particles reflect lighth. colloid particles also absorb ionsi. Brownian motion: the chaotic movement of colloidal particles
30 3. emulsions 1. colloidal dispersions of liquids in liquids 2 3. emulsions 1. colloidal dispersions of liquids in liquids 2. example: oil + soap