Copyright Pearson Prentice Hall Journal #7 Objective: To be able to identify acids and bases based on indicators and to understand how buffers work. 1. Explain the diagram below using your water vocabulary. 2. What characteristic of water allows spiders to walk on it’s surface? 3. What are the types of bonds that can form between atoms and what are the types of bonds between molecules? 4. Explain why water is a polar molecule. Copyright Pearson Prentice Hall

Solutions and Suspensions A mixture is a material composed of two or more elements or compounds that are physically mixed but not chemically combined. Copyright Pearson Prentice Hall

Solutions and Suspensions Two types of mixtures can be made with water solutions suspensions Copyright Pearson Prentice Hall

Solutions and Suspensions All the components of a solution are evenly distributed throughout the solution. Example: saltwater solution salt = solute—the substance that is dissolved. Water = solvent—the substance in which the solute dissolves. Copyright Pearson Prentice Hall

Solutions and Suspensions Cl - Cl - Na+ When an ionic compound such as sodium chloride is placed in water, water molecules surround and separate the positive and negative ions. Na+ Water Water Copyright Pearson Prentice Hall

Solutions and Suspensions Water's polarity gives it the ability to dissolve both ionic compounds and other polar molecules, such as sugar. Water is the greatest solvent on Earth. Copyright Pearson Prentice Hall

Solutions and Suspensions Some materials do not dissolve when placed in water but separate into pieces so small that they do not settle out. Such mixtures of water and nondissolved material are known as suspensions. Copyright Pearson Prentice Hall

Solutions and Suspensions Some of the most important biological fluids are both solutions and suspensions. Example: Blood is a solution and a suspension. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Here is a test tube with a blood sample that has been sitting and so all the suspended particles have settled out. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Acids, Bases, and pH Acids, Bases, and pH Water is neutral and breaks into two ions hydrogen ions (H+) = hydroxide ions (OH-) Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Acids, Bases, and pH The pH scale  The pH scale is to indicate the concentration of H+ ions in solution. The pH scale ranges from 0 to 14. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Acids, Bases, and pH The pH Scale At a pH of 7, the concentration of H+ ions and OH- ions is equal. Pure water has a pH of 7. Sea water Human blood Pure water Milk Normal rainfall The concentration of H+ ions determines whether solutions are acidic or basic. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Acids, Bases, and pH The pH Scale Solutions with a pH below 7 are called acidic because they have more H+ ions than OH- ions. The lower the pH, the greater the acidity. The concentration of H+ ions determines whether solutions are acidic or basic. Acid rain Tomato juice Lemon juice Stomach acids Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Acids, Bases, and pH The pH Scale Oven cleaner Solutions with a pH above 7 are called basic because they have more OH- ions than H+ ions. The higher the pH, the more basic the solution. Bleach Ammonia solution Soap Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Acids, Bases, and pH Acids An acid is any compound that forms H+ ions in solution.  Acidic solutions contain higher concentrations of H+ ions than pure water and have pH values below 7. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Acids, Bases, and pH Bases A base is a compound that produces hydroxide ions (OH- ions) in solution.  Basic, or alkaline, solutions contain lower concentrations of H+ ions than pure water and have pH values above 7. Copyright Pearson Prentice Hall

Base = produce OH- ions in solution (ex. sodium hydroxide) Acids & Bases Acid = compounds that release hydrogen ions (H+) in solution. (ex. HCl) Base = produce OH- ions in solution (ex. sodium hydroxide) Acid Base

Copyright Pearson Prentice Hall Acids, Bases, and pH Buffers  The pH of the fluids within most cells in the human body must generally be kept between 6.5 and 7.5. If the pH is lower or higher, it will affect the chemical reactions that take place within the cells. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Acids, Bases, and pH Controlling pH is important for maintaining homeostasis. One of the ways that the body controls pH is through dissolved compounds called buffers. Buffers are weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 2-2 Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 2-2 A molecule in which the charges are unevenly distributed is called a polar molecule. cohesive molecule. hydrogen molecule. covalent molecule. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 2-2 A dissolved substance is called a solvent. solution. solute. Suspension. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 2-2 A compound that produces hydroxide ions in solution is called a(an) base. buffer. acid. salt. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 2-2 Hydrogen bonds between water molecules result from adhesion between water molecules. magnetic attractions between water molecules. uneven electron distribution in each water molecule. ionic bonds in the water molecule. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 2-2 On a pH scale, a value of 2 means that the solution has equal concentrations of H+ and OH- ions. the same concentration of H+ ions as pure water. higher concentration of H+ than in pure water. lower concentration of H+ than in pure water. Copyright Pearson Prentice Hall

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