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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.
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2. Solutions and Suspensions
A mixture is a material composed of two or more elements or compounds that are physically mixed but not chemically combined.
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3. Solutions and Suspensions
Two types of mixtures can be made with water
solutions
suspensions
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4. 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.
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5. 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
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6. 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.
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7. 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.
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8. Solutions and Suspensions
Some of the most important biological fluids are both solutions and suspensions.
Example: Blood is a solution and a suspension.
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Here is a test tube with a blood sample that has been sitting and so all the suspended particles have settled out.
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Acids, Bases, and pH
Acids, Bases, and pH
Water is neutral and breaks into two ions
hydrogen ions (H+) = hydroxide ions (OH-)
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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.
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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.
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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
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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
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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.
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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.
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17. 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

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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.
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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.
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2-2
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2-2
A molecule in which the charges are unevenly distributed is called a
polar molecule.
cohesive molecule.
hydrogen molecule.
covalent molecule.
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2-2
A dissolved substance is called a
solvent.
solution.
solute.
Suspension.
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2-2
A compound that produces hydroxide ions in solution is called a(an)
base.
buffer.
acid.
salt.
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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.
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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.
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26. END OF SECTION