1. MYP Biology:
Water & It’s Properties

2. Water is Essential to Life on Earth
It is the ONLY substance on Earth that can be found naturally-occurring in all states of matter…
It makes up 60% of your body, 70% of your brain, and 80% of your blood…
It covers more than 70% of the planet, but less than 3% of it is drinkable…

3. What is the Structure of a Water Molecule?
H₂O
2 Hydrogen + 1 Oxygen
These atoms are linked together by COVALENT bonds in which they share electrons

4. What is the structure of a water molecule?
Hydrogen Atoms
Covalent Bond
Oxygen Atom

5. Water is a Polar Molecule
A Polar molecule has positive and negative “poles” due to unequal sharing of electrons in Covalent bonds

6. Water is a Polar Molecule
The larger atom(s) (Oxygen) pull more of the electrons toward it and takes on a negative (-) partial charge
The smaller atom(s) (Hydrogen) have electrons pulled away from them and take on a slight positive (+) partial charge

7. Water makes Hydrogen Bonds
Hydrogen bonds are between the oppositely charged ends of polar molecules (like water!)

8. Oxygen Atom
Covalent Bond
Hydrogen Atom
Hydrogen Bond

9. Many Compounds Dissolve in Water
Substances, like water, that other compounds dissolve in are called SOLVENTS.
The compounds being dissolved in the solvent are called SOLUTES.
Solutes and solvents mix together to form a SOLUTION.

10. A Solution: Salt & Water
SOLUTE (Salt)
SOLVENT (Water)

11. Many Compounds Dissolve in Water
Polar solvents dissolve POLAR solutes
Nonpolar solvents dissolve NONPOLAR solutes
Polar & Nonpolar do NOT mix…

12. Some Compounds form ACIDS or BASES
Acids release Hydrogen Ions (H+) when they dissolve in water
Bases remove Hydrogen Ions (H+) when they dissolve in water

13. Higher than 7 = BASIC (Alkaline)
Some Compounds form ACIDS or BASES
The pH Scale identifies how basic or acidic a solution is. The scale runs from 0 to 14.
Less than 7 = ACIDIC
7 = neutral
Higher than 7 = BASIC (Alkaline)

14. more acidic
stomach acid pH between 1 and 3

15. bile pH between 8 and 9
more basic

16. Water has many special properties
ADHESION & COHESION
Water molecules demonstrate ADHESION in their ability to stick to other surfaces and COHESION in their ability to stick to each other. This is due to the strong Hydrogen bonds they make.

17. Water has many special properties
SURFACE TENSION
The adhesive and cohesive properties of water produce SURFACE TENSION, or the ability of water molecules to form a thin surface ‘skin.’

18. Water has many special properties
HIGH SPECIFIC HEAT Water changes temperatures very SLOWLY. This is because it requires a large amount of energy to disrupt water’s strong network of Hydrogen bonds.

19. Water has many special properties
In most cases, the SOLID state of matter is the most dense:
But water is a special case…

20. Water has many special properties
SOLID Water is LESS Dense than LIQUID Water Due to the geometry of the Hydrogen bonds between water molecules, solid water (ice), is less DENSE than liquid water—so it floats!

21. Water has many special properties
“UNIVERSAL” SOLVENT
Since it is a POLAR molecule with neutral pH value, water is an excellent solvent and is able to dissolve most compounds.

22. Water’s properties make it essential to life
Adhesion / Cohesion
Water flows through tubes/ vessels from roots to tree-tops which allows plants to grow taller and transport water

23. Water’s properties make it essential to life
Surface Tension
Organisms can move across and live on top of bodies of water

24. Water’s properties make it essential to life
High Specific Heat
Stable environment for marine organisms
Acts as effective coolant (sweating)
Helps maintain homeostasis in terms of organism body temperature

25. Water’s properties make it essential to life
Ice is less dense than liquid water (floats)
Prevents water habitats from freezing solid
Preserves liquid water in colder temperatures
Ice reflects sunlight and regulates global temp.

26. Water’s properties make it essential to life
“Universal” Solvent
Dissolves and transports nutrients, gases, and waste through bodies of organisms and habitats

27. Check for Understanding!
pH = 7
Acid, Base, or Neutral?
pH = 3
pH = 13

28. Check for Understanding!
Oxygen Atom
Covalent Bond
Hydrogen Atom
Hydrogen Bond

29. Check for Understanding!

30. Check for Understanding!
Hot Water + Hot Chocolate Mix = Hot Chocolate
Solvent =
Water
Solute =
Chocolate Mix
Solution =
Hot Chocolate

31. The End…