Acids and Bases

Ok, let's first start off with a review shall we? What is the difference between an acid and a base you ask?Well, an acid tastes sour, are corrosive metals, change litmus paper to red, and overall become less acidic when a base is added. A base feels slippery, tastes bitter, changes litmus paper to blue, and as an acid is added to a base it becomes less basic. In an acid, it contains what we call a hydrogen atom( H+). We can also refer to this as a hydronium ion (H3O+) because when a hydrogen ion (H+) is added with a water molecule (H2O) it equals a positively charged hydronium ion of H3O+. On the other hand, bases produce what we call hydroxide ions when dissolved in water or (OH-). When a base dissolves in water it separates into a positive ion and a negative hydroxide ion. Take Ammonia for example(NH3) with Water (H20). The product equals NH4+ because when it gained a hydrogen proton it became an extra positive. But for the water, it lost a positive proton so it became a hydroxide ion ( OH-). As a result it became an Ammonia ion + Hydroxide.

Now that we learned about acids and bases, what do we call a substance that is neither? We call that a Neutral solution. But how do we determine if a substance is a neutral solution? Well, we use a pH scale or, a numerical scale used to indicate how acidic or basic a solution is. The scale runs from 0 to 14. Acidic solutions have pH below 7. Remember that highly acidic solutions have pH values near 0. Basic solutions have pH above 7. Highly basic solutions have pH values near 14. Neutral solutions, however, have a pH of 7. To get into further detail, The more acidic a solution the number of hydronium ion increases. The more basic a solution the number of hydroxide ion increases. Keep in mind that as one ion increases, the other decreases.

As we further increase our knowledge on the pH scale, there are some questions that come to mind. How is pH measured?

There are multiple answers. Some examples are through pH meters, pH strips AND CABBAGE JUICE.

A pH meter is an electronic instrument with an electrode that is sensitive to the hydronium ions in a solution. If you want an accurate measure of pH you need a pH meter.These can be taken outside labs for measuring pH in the environment such as lakes, streams and the ocean.

pH Strip Experiment

In this experiment we used substances of lye, baking soda, bleach, vinegar, and ammonia. We then put the litmus paper into each substance and await for the results. We found out that lye was purple and read that it has the pH number of 12, which results as a base. The baking soda turned out to be green along with bleach and ammonia. Both baking soda and bleach had the number 8 while ammonia has 9 and results as a base. Lastly, vinegar was a mixture of orange/red which read to be 3, and an acidic solution.

Cabbage Juice Experiment

In our next experiment we used boiled cabbage juice as our solution because it contains a natural pH indicator that changes colors according to the acidity of the solution.We then used the same materials as our last experiment and put tiny drops of them into small amounts of cabbage juice. We then compared them to each other. We kept in mind that the number is kept the same; just different colors or if you're lucky the same color.

Cabbage Juice Results

This is the result of our cabbage juice experiment. Starting at the right, the pink as vinegar. When comparing this (pink) with vinegar pH strip (orange/red) there was a difference of about 2. Going down, below pink is a green substance of ammonia. Turns out both pH strip and Cabbage Juice were about the same color. Below ammonia is bleach which also has green when comparing it with the pH strip. Now the yellow one was lye. When looking at a pH scale the color yellow is about 7. When comparing that with the litmus paper, purple 12, there is a huge difference and sums up why a pH meter is a very handy tool. Next to the bottom yellow to the right, we have baking soda. No excitement there folks. When comparing, with the litmus paper they both have the same color.

Another way to measure pH is through pH strips or litmus paper. Litmus is one of the simplest indicator test papers, but provides the least information. Recall that blue litmus paper will turn red in acid solutions and red litmus paper will turn blue in basic solutions. No change in colr occurs if the solution is neutral.