Or, How Even a Small H+ Ion Can Make a Huge Difference

Acids & Bases Or, how even a small H+ ion can make a huge difference Why?

Acids and bases are an important topic for biologists. Even a slight change in the acidity of a solution (our blood for example) can mean the difference between life and death. Activating Prior Knowledge In the space below, write down and/or sketch everything you know, or have heard about, acids and/or bases.

1 Model 1- What’s Happening

a. By now you know the shape of a water molecule, and that its uneven distribution of electrons makes it polar.

b. You also know that water molecules “stick” together like magnets to form weak but plentiful hydrogen bonds (represented by the dotted lines) between oxygen and hydrogen atoms.

c. What you may not know is that when water molecules are bound together with hydrogen bonds, sometimes the attraction between oxygen and hydrogen is so strong, the oxygen literally pulls a hydrogen atom from another oxygen atom forming a hydronium and hydroxide ion..

d. If the # of H+ and OH- ions are the same, the solution is neutral. e. If the # of H+ions are greater than OH- ions, the solution is acidic. f. If the # of OH- ions are greater than H+ ions, the solution is basic. 1. Considering the information in Model 1d-1f, tell if the solutions in each diagram would be neutral, basic, or acidic.

3 Read This! The strength of an acid depends on the number H+ ions in the solution. The more H+ ions, the stronger the acid will be.

The strength of a base depends on the number of OH- ions in the solution. The more OH- ions, the stronger the base will be. 2. Consider the information above, and rank the acids below from strongest to weakest.

3. Consider the information above, and rank the bases below from strongest to weakest.

Read This! The pH scale measures how acidic or basic a substance is. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is basic. The pH scale is logarithmic and as a result, each whole pH value below 7 is ten times more acidic than the next higher value. For example, pH 4 is ten times more acidic than pH 5 and 100 times (10 times 10) more acidic than pH 6. The same holds true for pH values above 7, each of which is ten times more alkaline (another way to say basic) than the next lower whole value. For example, pH 10 is ten times more alkaline than pH 9 and 100 times (10 times 10) more alkaline than pH 8. 4. Use the pH test strips and scale to test the substances provided. Substance pH Acid or Which means it has Base? more H+ or OH- ions?

5. Conclusion: List all your tested substances from MOST ACIDIC TO LEAST ACIDIC:

6. Do you think a solid can be an acid or a base? Why or why not?