![]() ![]() The items above can be used to measure pH for science projects and other hobby and home applications. For example, when creating buffers for a biotechnology project. Suitable for more advanced research where the exact pH of a solution matters. We recommend checking if there is one available at your local high school chemistry laboratory before purchasing. For example, a range suitable for aquatic organisms. Suitable for more advanced research where the objective is to get a solution within a narrow range. Suitable for intermediate level projects where the objective is to watch how the pH of a solution slowly changes. Suitable for most beginner level project when the objective is to find out simply if something is acidic or basic. Hydrion (9800) Spectral 0-14 Plastic pH Strip Table 2 below discusses what types of pH measuring devices are best for different science project applications, and offers a quick link to purchasing different pH test papers and indicator sticks. pH meters are even more precise than pH test paper or indicator sticks. They consist of a probe that is dipped in a solution, and a digital readout. pH meters are electronic devices that used to measure pH. An example of a used pH indicator stick and the corresponding color key is shown below in Figure 1. Each color on the key represents a different pH. The color of the dipped paper/stick is then matched to a color key that comes with the container of pH test paper or indicator sticks. To measure pH, a piece of pH test paper or an indicator stick is dipped into the liquid. pH test paper and indicator sticks are pieces of paper or stiffer sticks that contain pH indicators (chemicals that change color depending on how acidic or basic a solution is). Measuring pH can be done simply and quickly using pH test paper, pH indicator sticks, or a pH meter. The pH of a liquid or solution is often an important piece of information in science. The pH Scale: Some Examples Measuring the pH How do you measure pH? ![]() To be more precise, pH is the negative logarithm of the hydrogen ion concentration: It's a lot easier to use a logarithmic scale instead of always having to write down all those zeros! By the way, notice how one hundred million million is a one with fourteen zeros after it? It is not coincidence, it is logarithms! The pH scale is theoretically open-ended but most pH values are in the range from 0 to 14. ![]() Each one-unit change in the pH scale corresponds to a ten-fold change in hydrogen ion concentration. In order to deal with these large numbers more easily, scientists use a logarithmic scale, the pH scale. Moreover, the hydrogen ion and hydroxide ion concentrations in everyday solutions can vary over that entire range. Here is why: a strongly acidic solution can have one hundred million million, or one hundred trillion (100,000,000,000,000) times more hydrogen ions than a strongly basic solution! The flip side, of course, is that a strongly basic solution can have 100,000,000,000,000 times more hydroxide ions than a strongly acidic solution. What is pH?Īcidity and alkalinity are measured with a logarithmic scale called pH. Because the base "soaks up" hydrogen ions, the result is a solution with more hydroxide ions than hydrogen ions. When a base is dissolved in water, the balance between hydrogen ions and hydroxide ions shifts the opposite way. This kind of solution is acidic.Ī base is a substance that accepts hydrogen ions. Now there are more hydrogen ions than hydroxide ions in the solution. Because of this, when an acid is dissolved in water, the balance between hydrogen ions and hydroxide ions is shifted. The solution is neither acidic or basic.Īn acid is a substance that donates hydrogen ions. In pure water, there are an equal number of hydrogen ions and hydroxide ions. For simplicity, hydronium ions are referred to as hydrogen ions H +. The "lost" hydrogen ions join up with water molecules to form hydronium ions (H 3O +). Some of the water molecules lose a hydrogen and become hydroxide ions (OH −). In water (H 2O), a small number of the molecules dissociate (split up). Whether a liquid is an acid or a base has to do with hydrogen ions (abbreviated with the chemical symbol H +). Acidic or Basic? What is an acid or a base? ![]()
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