1. Water is the medium of life

3. Water 2 Hydrogen atoms + 1 Oxygen atom covalently bonded (polar)
Makes up 70-95% of living things, covers 75% of Earth
DRAW and LABEL this in your notes

4. Water Molecules & Their Bonds
The bonding of hydrogen and oxygen involves the sharing of electrons but not equally
Oxygen has 8 protons & hydrogen 1/atom

5. Water Molecules are Polar
The e are shared unequally, creating an unequal distribution of charge
Hydrogen becomes more partially charges & oxygen more negatively charged

6. Hydrogen Bonding
The bonds are made and broken quickly as the molecules move, however the large numbers of bonds contribute to the stability of water

8. Properties of Water Ice
Solid water (ice) is less dense than liquid water therefore, ice floats
Caused by hydrogen bonds forming between water molecules and becoming stable

9. Properties of Water Transparency
Light penetrates tissues and aquatic environments/ important for photosynthesis

10. Parts of Solutions Solution: a liquid mixture of 2 or more substances
Aqueous solution: liquid in which water is the solvent
Solvent: dissolving agent of solutions
Solute: substance being dissolved

11. Solvent
Water can dissolve many organic and inorganic substances that have charged or polar regions
The polar attraction of large quantities of water molecules can interrupt intra-molecular forces (such as ionic bonds) and resulting in the dissociation of the atoms

12. Solvent
Positive atoms, e.g. Na+ end up being surrounded by the negative oxygen regions of water molecules and the Cl- being surrounded by the positive hydrogen region of water molecules.

13. Solvent
Cells are mostly water therefore diffusion into and out of them happens most easily if the substance concerned is in solution, e.g. before oxygen diffuses from the alveoli to the blood it dissolves into the moist layer lining the alveoli.

14. What kind of bear dissolves in water?

15. Water “Loving” Hydrophilic: any substance with an attraction to water
Substance does not have to dissolve
EX: cotton
Substances can dissolve
EX: glucose, sodium

16. Water “Fearing”
Hydrophobic: any substance which repels water (insoluble)
Molecules have to negative or positive charges (nonpolar)
Ex: vegetable oil

17. Transport of Molecules in Blood
Glucose is a polar molecule & freely soluble
Blood plasma consists mainly of water (95%) plus dissolved substances which it tranports

18. Transport of Molecules in Blood
Amino Acids
Positive & negative charges (dues to the amine & acid groups) therefore soluble in water
R group varies , can be polar, non-polar or charged
R group determines the solubility
Carried by the blood plasma

19. Transport of Molecules in Blood
Oxygen
Non-polar
Soluble in water, but just
Water becomes saturated with oxygen at relatively low concentration
As temp. increases the solubility decreases
Haemoglobin in red blood cells carry the majority of oxygen

20. Transport of Molecules in Blood
Fats
Large, non-polar molecules
Insoluble in water
Carried in blood inside lipoprotein complexes
Cholesterol
Molecules are hydrophobic except for a small hydrophilic region at one end
Not enough to make cholesterol dissolve in water
Carried in blood in lipoprotein complexes

21. Transport of Molecules in Blood
Sodium Chloride
Ionic compound
Freely soluble in water
Dissolving to form sodium ions and chloride ions
Carried in blood plasma

22. Nature of Science
Use theories to explain natural phenomena – the theory that hydrogen bonds form between water molecules explains the properties of water.
The observable properties of water are explained by cohesion, adhesion, solvent and thermal properties, which are in turn explained by hydrogen bonding.

23. Properties of Water Cohesion
Created by the constant forming and reforming of hydrogen bonds between water molecules
Creates a more structurally organized liquid
Enables water to move against gravity

24. Properties of Water Cohesion
Explains how water molecules can form a chain in delivering moisture to the top of a tree or through the blood stream

25. Properties of Water Surface Tension
A measure of how difficult it is to stretch or break the surface of a liquid
Water has a greater surface tension than most other liquids

26. Properties of Water Adhesion
Created by the clinging of one substance to another
Water molecules tend to stick to other molecules that are charged or polar for similar reasons that they stick to each other
Water adheres to the walls of vessels to counter the downward pull of gravity

27. Properties of Water Moderating Temperatures
Stabilizes air temperature by absorbing heat from warmer air and releasing the stored heat to the cooler air
Used as the basis for Celsius scale to indicate temperature
Water freezes at 0o and boils at 100o

28. Properties of Water Specific Heat
Amount of heat absorbed or lost for 1g of substance to change temperature of water 1o
Water’s specific heat is 1 cal/g/oC (10 times that of iron)
Must absorb or release a relatively large quantity of heat for temperature to change
Organisms made mostly of water resist temperature changes

29. Thermal Properties
Water is used by leaves as a coolant. The heat loss from leaves for evaporation prevents them over-heating. If the leaves get too hot enzymes in their cells will start to denature.

30. Evaporative Cooling
Vaporization (evaporation): transformation from liquid to gas
Helps to protect terrestrial organisms from overheating (sweating)
Contributes to stability of temperatures in lakes and ponds
Helps moderate climate on Earth

31. Heat of Vaporization
the quantity of heat that must be absorbed for 1g of liquid to be converted to a gas
Water’s is high at 580 cal/g
Due to large amount of heat needed to break hydrogen bonds

32. Water Molecules A water molecule can dissociate into two parts:
Hydrogen ion: H+
Hydroxide ion: OH-

33. pH Acids: substances which increase H+ concentration of a solution
Ex: Nitric Acid: HNO3
Bases: substances which increase OH- concentration of a solution
Ex: Sodium hydroxide: NaOH
Buffers: substances that minimize changes in pH

34. pH Scale Range from 0-14 Acids are 0-6 Ex: gastric juice 2, urine 6
Bases are 8-14
Ex: ammonia 13, sea water 8.5
Neutrals are at 7
Ex: Pure water, human blood is very close

35. Water & Methane Methane
Waste product of anaerobic respiration in certain prokaryotes living in anaerobic conditions
Can be used as a fuel
If present in the atmosphere it contributes to the greenhouse gases

36. Review