Baking SodaBaking Soda

Objective:

Identify two household acids and two household bases.

Discription:

Acids and bases

Acids have a pH 6 balance or lower. Acids are proton donors and bases are proton acceptors. Most acids will taste sour and will change litmus paper from blue to red. When acids are mixed with certain bases such as salt there will be a reaction.

Bases have a pH 8 balance or higher. Bases usually taste bitter and have a slippery feel or texture to them. Bases will not change the color of litmus paper. However, they can change the litmus paper back from red to blue. Bases will react with acids to form salts and water.

I am going to help my students learn through a laboratory activity using different acids and bases. This activity is meant for junior high to college level students. Students will test various household products to determine their pH level. Students will use pH paper to determine if the substance is a base or an acid using the pH scale as stated above. The tool I am using was used in my Physics 1090 class and has been modified.


Barrans, R.,Physics 1090: Activities Manual Fall 2009, Laramie, Wy:The Copy Center,pp.136

Impletmentation:

Students will use various household chemicals and test their pH and record their results in a table provided by the teacher. The teacher will set up different tables with an acid or base on each table that can be found at a local store. pH paper will be at each table at each table. A new pH paper must be used for each test. Students will record each result in a hand out provided by the teacher. Prior to letting the students conduct the activity I will go over the lab and procedures for the activity with entire class. Safety rules will be given during this time such as where the eyewash stations are located and safety goggles are required. Wastes can be poored out after the activity and properly wash all items afterward with soap and water. No horse play will be tolerated. The students will then conduct the activity. There is no parental permission required to do this activity with the items listed however, some of the chemicals could irritate the skin or injure the eyes. Be sure to wear safety googles and wash all areas that come in contact with substances from bleach and ammonia. Before the students being they will look at the tool provided with the list of items that will be tested. The students will predict what items will be acids and what items will be bases before they perform the activity. After each one is tested they will record their results and see if their predictions were correct. The students will use a glass rod to dip into the household products and then touch the rod to a piece of pH paper. The students will compare the results from the paper to the color chart for the pH paper to help decide if the paper is a base or an acid. From this tool students will gain a better understanding of pH levels of common household chemicals and know what a base is and what an acid is. After the class has completed the activity, I will give a wrap up of the lesson explaining how the pH scale works. This is the time to be sure the students understand the lesson activity.

Students Predictions Chemicals Base or Acid
Acid Vinegar Acid
_______ Window Cleaner_______
_______ Shampoo_______
_______ Bleach_______
_______ Ammonia_______
_______ Milk_______
_______ Soda_______
_______ Lemon Juice_______
_______ Conditoner_______
_______ Coffee_______
_______ Vinegar_______
_______ Salsa_______
_______ Gatorade_______

Evaluation:

In order for the students to grasp the concept they will need prior knowledge of acids and bases and how the pH scale is used. Having the students work with household chemicals can help them better grasp which are acids or bases, this learning tool does a good job completely addressing the objective. By using this laboratory I feel it would give students a good hands on tool for learning the pH system and let the students get involved instead of just lecturing. Over all, the laboratory for this activity would work well with a lecture before the activity and a follow up afterwards. The downside of this activity is that it can be time consuming with the lecture, laboratory and the follow up and will take multiple classes. The teacher would also need to be present at all times with this activity.This activity could be used with lower grade levels with some restrictions. The teacher would be the one to conduct the experiments in front of the class for the students.Students of different learning abilities should still be able to master the objective. If necessary the instructor can group these students with others of higher abilities to help guide them. Students will most likely have misconceptions of what is a household acid or base from this learning tool. Having students test the household chemicals with pH strips and see the results first hand should curb any remaining misconceptions.

Costs:

This learning tool can be inexpensive to implement in the classroom. You can buy the various household chemicals at Wal-Mart. The pH test strips can be purchased online at Amazon.com. With a one time purchase of these items this tool could be used several times making this a cost effective learning tool.