Acids & Bases

The number of OH- & H+ are the same when the pH is 7 (neutral)!

What do you think will happen to the pH if acid is added to the solution?

What do you think will happen to the pH if base is added to the solution?

pH scale pH scale is logarithmic meaning it is on a scale that increases 10 times for each number.

pH scale

Acids Common acids – lemons & oranges contain citric acid An acid is a substance that reacts with metals to release hydrogen.acid Usually sour tasting (don’t taste things in the lab though!), and react with metals Sour milk contains lactic acid. Vinegar contains acetic acid.

Bases “Alkalines” Bases taste bitter and feel slippery. Milk of magnesia, ammonia, and soap are bitter tasting substances that contain bases. Like acids, strong bases are dangerous. They can burn the skin. The hydroxyl ion, OH, is a negative ion made up of one atom of hydrogen and one atom of oxygen. All bases release hydroxyl ions in water.hydroxyl ions Hydroxyl ions can combine with hydrogen ions to form water. Bases are often called proton acceptors. (Remember that a hydrogen ion is a proton.)

Indicators Chemicals that change color in acids or bases are called indicators. Litmus paper is an indicator that turns red in acids and blue in bases. Vinegar is an acid. If you dip one end of a strip of blue litmus paper into vinegar, the blue litmus turns red. If you dip one end of a strip of red litmus paper into soapy water, the red litmus turns blue.

Indicators Many common, everyday substances are indicators. Hydrangeas have pink flowers in basic soil and blue flowers in acidic soil. Red cabbage, beets, rhubarb, cherries, blueberries, and blackberries all can be used as indicators.

pH in blood between 7.35 and 7.45 As with all waste products, carbon dioxide gets excreted into the blood. The blood carries carbon dioxide to the lungs, where it is exhaled. As carbon dioxide accumulates in the blood, the pH of the blood decreases (acidity increases). The brain regulates the amount of carbon dioxide that is exhaled by controlling the speed and depth of breathing. By adjusting the speed and depth of breathing, the brain and lungs are able to regulate the blood pH minute by minute.

pH in stomach 1-3 The pH (a measurement of acid levels) in the stomach is normally very low, indicating a high level of acid. The acid, which is released by cells in the stomach, is necessary to help break down foods and aid digestion. Although high levels of acid can injure other areas of the digestive tract, such as the esophagus, the stomach itself is protected by the mucus that coats its walls. Ex. heartburn or gastroesophageal reflux disease, This sudden change in pH is the cause of the irritation and injury to the esophagus.

pH in Cells Usually around pH 7 Varies depending what the function of the cell is & where it is located! When a cell ‘commits suicide’ it actually exposes an organelle (lysosome) which is has a low pH (around 4), and it ‘eats’ the rest of the cell.

Buffers Many biological fluids contain buffers, substances that cause a solution to resist changes in pH. A buffer works by accepting H+ ions when their levels rise and donating H+ ions when their levels fall, thereby maintaining a fairly constant pH in the solution. Kidneys & lungs help maintain pH in body

Alkalosis Blood pH of above 7.45 Over excitability of central nervous system Caused by aspirin overdose & by other drugs Symptoms are stroke, vomiting, hyperventilation

Acidosis Blood pH of less than 7.35 Over excitability of central nervous system Caused by intense workout, poor circulation & breathing in the elderly, crash dieting, & kidney failure.

Acidosis Can be caused by…… Sugar breaking down produces lactate as a waste product which reacts with water to form lactic acid. When working out, if oxygen can’t get to the cell fast enough, the cells start breaking down sugar without using oxygen. This occurs in muscle tissue and results in lactic acid being produced. Breakdown of fats releases acidic by-products & they build up in the body.

Review 1. Explain how the structure of water molecules results in attractions among them. 2. Give an example of how cohesion among water molecules is important to living things. 3. Describe the information the pH scale provides. 4. Name three conditions on Earth that make the planet suitable for life. 5. Explain one way in which water can moderate temperature.

Review Analyzing Data Use the data table below to answer the following questions. a. Which sample in the table is most acidic? b. Which sample listed has a pH that is closest to neutral? c. In equal volumes of normal rainfall and baking soda solution, which sample would have a greater amount of hydrogen ions (H+) present? Explain.

Evaluating Promotional Claims Suppose a cosmetics manufacturer advertises a shampoo as "having a pH as gentle as rainwater." Describe how you might determine whether the promotional claim is valid.