Acids and Bases Lesson 15

Acids Acids are traditionally considered any chemical compound that, when dissolved in water, gives a pH of  less than 7.0. They also: Taste sour Are good conductors of electricity (they release H+ ions when they are in water) React with compounds that contain carbonate Are generally quite reactive Turns litmus red React with bases

Acids Acids are widely used in industry, they are used in many manufacturing processes including; fertilizers, explosives, refining oil, and electroplating materials.

Table 1 : Examples of common acids Common name Formula Source or use Vinegar (acetic acid) HC2H3O2 Salad dressing Citric acid HC6H7O7 Oranges, lemons Ascorbic acid HC6H7O6 Vitamin C Lactic acid HC­3H5O3 Sour milk or tired muscles Sulfuric acid H2SO4 Car batteries

Base A base is most commonly thought of as an aqueous substance with a pH higher than 7.0 at standard conditions. They also: Taste bitter Are good conductors of electricity (They release OH- ions when dissolved in water) Break down proteins into smaller molecules May also be called alkaline Turns litmus blue React with acids

Table 2 Examples of some common bases Common Name Formula Source or use Sodium hydroxide NaOH Drain cleaner Potassium hydroxide KOH Soap, cosmetics Aluminum hydroxide Al(OH)­3 Antacids Ammonium hydroxide NH­­4OH Window cleaner.

pH The pH scale is used to represent how acid or basic a solution is. The scale ranges from 0-14 with very acidic being 0, neutral being 7, and very basic being 14.

pH

Chemical Changes with Acids and Bases Yeast is called a raising agent. The carbon dioxide it produces “raises” the bread and makes it lighter. Baking powder is another type raising agent. Baking powder is often used in making cakes and cookies because it works fast than yeast.

Baking soda is a base. Vinegar is an acid. Mixing them together produces a bubbling action. Baking powder releases carbon dioxide in the same way.

Ingredients: Cream of tartar (acid) Baking soda (base) Corn starch (filler)

The filler keeps the acid and base separated The filler keeps the acid and base separated. The filler also absorbs any moisture that might get into the baking powder. When you add a liquid such as water to baking powder, the dry acid and dry base dissolve. The acid and base react to produce carbon dioxide bubbles.

Questions: What is baking powder used for? Why is corn starch added to baking powder? Why isn’t vinegar used as the acid in baking powder?

Raising Agent Lab Question Which raising agent produces carbon dioxide the fastest? Safety precautions Clean up the work area and wash your hands thoroughly at the end of the activity. Never eat anything that has been made in a science room

Experimental Design Use the tape and pencil to label the three beakers: baking soda, vinegar, and baking powder. Add raising agent to its cylinder Add 25 mL of egg white solution to each cylinder Swirl each cylinder gently to mix Measure the height of the foam in each cylinder every three minutes for 9 minutes Record the results in the table.