• 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

Water

• 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

Special Properties of Water

• 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 SiO2 or the cellulose tubes of paper)

– This helps to explain the meniscus inside a tube

Special Properties of Water

Cohesive-Adhesive Properties of Water

Cohesive-Adhesive Properties of Water

Cohesive-Adhesive Properties of Water

Cohesive-Adhesive Properties of Water

Cohesive-Adhesive Properties of Water

• 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.

Special Properties of Water

• 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 . ℃• cwater = 4.18 J/g‧℃

• This is high compared to other substances: ccopper = 0.385 J/g‧℃ cair = 1.00 J/g‧℃cglass = 0.735 J/g‧℃ ciron = 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.

Special Properties of water

• Moderation of climate

• This property of water also helps to moderate temperature changes in cells

Specific heat capacity of water

• 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.

• Lf water = 334 J/g

• Lv water = 2260 J/g

Special Properties of water

Latent heat

• Evaporative cooling relies on Lv of water.

Latent heat of vaporization

• 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

• 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

HOMEWORK

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