Testing for pH

What we will be doing: We will be using an indicator to test the pH of certain substances. An indicator is a substance that changes color in the presence of Acids or Bases. Our indicator will be red cabbage solution. We will then mix red cabbage solution with several substances and record the color change.

How does it work? Red cabbage contains a pigment known as flavin that changes color in the presence of acids or bases. We can then use red cabbage to indicate whether something is an acid or a base.

Lets see an example! https://www.youtube.com/watch?v=wiD g1QTHjHM

Some things we will be testing: Lemon Juice Sprite Vinegar Baking Soda solution Green Cleaner solution Sugar water

Our Indicator: pH Color 2 Red 4 Purple 6 Violet 8 Blue 10 Blue-green 12 Greenish-yellow

Testing for Acids and Bases To begin, start adding one of each of your household items to a different cup containing cabbage solution. Since each table has two set of cups, each person should work with the person next to them at the table! So, add one of each labeled plastic cup to a different cup containing cabbage. Once you have added everything together, record the results in the table in your handout.

What are we looking for? Therefore if a solution is acidic, it will be a reddish color, and if it is basic, it will be a greenish-yellow color. If it is neutral, it will be a blue color. Use the table in your handout as a guide when recording the results of your solutions.

Is it an acid or base? Now that you have recorded the color of each of your solutions, determine which ones are acids and which ones are bases. Remember, the lower the pH, the more acidic a solution is. The higher the pH, the more basic a solution is.

Solution Acid/ Base/ Neutral Sprite Baking Soda Lemon Juice Vinegar Color Sprite Baking soda Lemon Juice Vinegar Green Cleaner Sugar Water Solution pH Sprite Baking soda Lemon Juice Vinegar Green Cleaner Sugar Water Solution Acid/ Base/ Neutral Sprite Baking Soda Lemon Juice Vinegar Green Cleaner Sugar Water

Lets Make a Graph! Now that we’ve determined which solutions are acids, bases, or neutral, lets make a graph to show what we found! Place your acids on the left, neutral solutions in the middle and bases on the right.

Solution pH Sprite Baking soda Lemon Juice Vinegar Green Cleaner Sugar Water

Mentos and Diet Coke Next we will be combining Mentos and diet coke and observing the reaction. Write down what you see happening.

Question Why do you think the diet coke fizzes up when you drop a Mentos in it?

How does it work? Mentos contain hundreds of tiny pours on its surface. When you drop one in Diet Coke, it causes a reaction with the CO2 in the soda to release a gas that causes the volcanic reaction. A chemical reaction!

Lets See what Myth Busters Has To Say! http://www.youtube.com/watch?v=LjbJE LjLgZg