1. Water is not an organic molecule but is essential for life on this planet All cells are surrounded inside and out with water – anything that interacts with a cell must first be dissolved in water Physical properties: – colourless and transparent – liquid at room temperature – density = 1.0 g/mL – m.p. = 0 ℃ b.p = 100 ℃ water has LD, D-D forces, and H-bonding

2. Water has cohesive properties – the high number of intermolecular forces causes water molecules to ‘stick’ together Examples: – surface tension – beading of water – water striders – too light to break surface tension – transpiration in plants – transport in xylem tubes

3. Water has adhesive properties – it’s polar nature causes it to stick to other substances Examples: – capillary action – water ‘climbs’ up small diameter tubes, or ‘bleeds’ through the microscopic pores and channels in paper or other porous substances – this is due to the hydrogen bonding interactions between the water and the surface of the tube (either SiO 2 or the cellulose tubes of paper) – This helps to explain the meniscus inside a tube

9. Water has outstanding solvent properties Used to be called the ‘universal solvent’, but this is not a good name, since not everything dissolves in water The polar nature of water allows any other polar substance or any charged particle to dissolve easily The δ - will attract the δ + end of solutes, and this attraction will remain once the solute is dissolved. The same is true for ionic substances – the cation will be attracted to the δ - end of water, and the anion will be attracted to the δ + of water.

11. Water has a high specific heat capacity This is a measure of the amount of heat energy required to increase the temperature of a 1g of a substance by 1 ℃. c water = 4.18 J/g ‧℃ This is high compared to other substances: c copper = 0.385 J/g ‧℃ c air = 1.00 J/g ‧℃ c glass = 0.735 J/g ‧℃ c iron = 0.450 J/g ‧℃ A metal pan absorbs heat energy quickly and loses it quickly. This makes metals useful for cooking. Water takes more energy to heat up – thus the time it takes to boil water in a pot.

12. Moderation of climate This property of water also helps to moderate temperature changes in cells

13. Water has a high latent heat of vaporization and fusion. Latent heat is the energy absorbed or released by a substance during a change of state. L f water = 334 J/g L v water = 2260 J/g Special Properties of water

14. Latent heat

15. Evaporative cooling relies on L v of water. Latent heat of vaporization

16. Tender fruit farmers take advantage of the latent heat of fusion of ice when there is a chance of frost On an evening when there is frost in the forecast, they spray water over their fruit, causing ice to form as the temperature drops below 0°C. How does this help to protect the fruit? Latent heat of fusion

17. Water’s density decreases as it changes from liquid to solid. This is because the distance between molecules in a crystal lattice (as ice) on average further than when in a liquid. Special Properties of water

18. HOMEWORK Read and Summarize Page: 195 “Salt and Ice” Pages: 196-197 Unuaual Properties of Water Questions page 198 # 1,11