1. Water & pH
Packet #7
Chapter #2

2. Introduction Most abundant liquid in the world
Makes up at least half of all living organisms and up to 95% of some species.
75% of earth is submerged in water
Naturally occurring water consists of 99.76% H2O
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3. The Water Molecule
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4. Properties of Water
Density

5. Density Water has a maximum density at 4ºC
This is when water is in a liquid state
The density will be 1.
H2O (l) is more dense than H2O (s)
Water freezes from top downward allowing ice to form at the top
Ice at top can insulate the warmer water below that layer from colder temperatures above
Prevents large bodies of water from freezing solid and allowing the survival of aquatic organisms
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6. Properties of Water
Cohesion and Adhesion

7. Cohesion & Adhesion Cohesion Adhesion HW Assignment
Attraction of molecules of the same substance.
The hydrogen bonding allows water to be cohesive
Causes individual water molecules on the top to be drawn inward allowing for the appearance a smooth surface
Adhesion
Attraction of molecules of different substances.
Example of water in a graduated cylinder.
HW Assignment
Define capillary action and relate it to the concept of adhesion.

8. Properties of Water
Solubility

9. Solubility Water is a versatile solvent due to its polarity
Can form an aqueous solution
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10. Definitions
Mixture
A portion of matter that can be separated into two or more substances by physical means alone
Substance composed of 2 or more elements or compounds that are mixed together, but are not chemically combined
The two substances can be separated
Salt and pepper
Sugar and sand
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11. Definitions II Solution
A homogeneous (of uniform structure or composition throughout ) mixture of two or more substances, which may be solids, liquids, gases, or a combination of these.
Homogenous mixture
Sugar in water (Sugar-water)
One component (Major), of a solution, is found in a greater amount
Solvent
One component (Minor), of a solution, is found in a lesser amount
Solute
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12. The different regions of the polar water molecule can interact with ionic compounds called solutes and dissolve them
Negative oxygen regions of polar water molecules are attracted to sodium cations (Na+). +
Cl – –
Na+
Positive hydrogen regions of water molecules cling to chloride anions (Cl–).
Cl–
Figure 3.6
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13. Solubility “Likes dissolves likes” Oil and water are dislikes
Polar with polar
Non-polar with non-polar
Oil and water are dislikes
Water = polar
Oil = non-polar
We say that oil and water are nearly completely immiscible
The oil is suspended
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14. Other Important Points II
Hydrophilic substance
Water loving
Has an affinity for water
Hydrophobic substance
Water hating
Does not have an affinity for water
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15. pH

16. pH
The pH scale will tell us how willing a compound is in giving hydrogen ions (H+)
Bronsted-Lowry Acid
A substance that donates a hydrogen ion (H+)
An acidic solution has a higher concentration of H+ than pure water and have pH values below 7
Bronsted-Lowry Base
A substance that accepts a hydrogen ion (H+)
A basic, or alkaline solution, contain lower concentrations of H+ than pure water and have pH values above 7.
Illustrate showing water as an example, or, HCl in water
H3O+ (Hydronium)
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17. Acid Base Reaction Using H2O (Base) and HCl (Acid)
H2O = Water
HCl = Hydrochloric Acid
The hydrogen in the compound HCl donates/gives it’s electron to Cl
Hydrogen will have a positive charge because it is missing an electron and Chlorine will have a negative charge because it has gained an electron (These are called ions; H+ and Cl-)
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18. Acid Base Reaction Continued
The oxygen atom, located in the water molecule and is electronegative, decides to give the Hydrogen ion an electron
Hydrogen attaches to H2O to make H3O+
It has a positive charge because the Hydrogen ion attached missing an electron
H3O+ is called the Hydronium ion
In the end as a result of the Acid-Base Reaction, the end produces are H3O+ and Cl-

19. Acid Base Reaction

20. pH Scale
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21. pH Scale II