Water & pH Packet #7 Chapter #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 Friday, November 16, 2018

The Water Molecule Friday, November 16, 2018

Properties of Water Density

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 Friday, November 16, 2018

Properties of Water Cohesion and Adhesion

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.

Properties of Water Solubility

Solubility Water is a versatile solvent due to its polarity Can form an aqueous solution Friday, November 16, 2018

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 Friday, November 16, 2018

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 Friday, November 16, 2018

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 Friday, November 16, 2018

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 11/16/2018 9:52:19 AM11/16/2018 9:52:19 AM 13 Friday, November 16, 2018

Other Important Points II Hydrophilic substance Water loving Has an affinity for water Hydrophobic substance Water hating Does not have an affinity for water Friday, November 16, 2018

pH

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) 11/16/2018 9:52:19 AM

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-) 11/16/2018 9:52:19 AM

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-

Acid Base Reaction

pH Scale 11/16/2018 9:52:19 AM

pH Scale II