Acids and Bases

What is an Acid?

An acid is a substance with the following properties:

  • Sour taste
  • Turns red or yellow when reacting with a pH indicator
  • Gives off hydrogen ions when reacting with water

Lemons and oranges contain an acid called citric acid, which is why they taste sour. Luckily, our stomach is covered in a substance that prevents the acid from reacting with our stomachs.

What is a Base?

A base has opposite properties than acids:

  • Bitter taste
  • Turns¬†blue or purple when reacting with a pH indicator
  • Feels soapy
  • Give off hydroxide ions(OH-) when reacting with water

pH Scale

The pH scale is used to measure the acidity/alkalinity of an object. pH stands for potential hydrogen; a fitting name, considering that it is measuring the amount of hydrogen ions an object has. It consists of a color chart that is numbered from 1-14, with 1 being the most acidic and 14 being the most basic. The acids are identified with colors red, yellow, and orange. The more acidic a substance is, the darker it will be. Bases are identified with the colors blue and purple. The more basic a substance is, the more purple it will be.

For example, battery acid has an acidity level of 0(extremely acidic), so it will be dark red; the darkest shade of red on the chart. Lemon juice as an acidity level of around 2, so it will be represented as a light shade of red or dark shade of orange. Coffee has an acidity level of 5, so it will be represented as a light shade of green or yellow.

In the same way, the alkalinity of an object is represented by its color. and number on the chart. If an object has a pH level of 7, it is neutral; neither acidic, nor basic. Distilled water is neutral, and has a pH level of 7.

pH Indicators

There are many things that you can use to find out if a substance is acidic of basic. Litmus is a substance that would work. Mix litmus with the substance being tested. You can figure out its acidity or alkalinity level based on what color it changes into.

Litmus is called a pH indicator, because it tells us if a substance is acidic or basic. Other examples of pH indicators are bromothymol blue, and universal indicator.

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