The pH scale is a measure of the concentration of acid or base a substance contains. By definition, the pH scale is the concentration of the hydrogen ion. The hydrogen ion is a characteristic of acids. High hydrogen ion amounts indicate high acid concentration, low hydrogen ion amounts indicates a basic concentration. The scale is graduated from 0-14. The numerically low end, 0-6.9, is the acid end. The closer the pH is to zero indicates a greater acid concentration. The mid point on the scale is 7; having equal amounts of acid and base making a neutral substance.
pH can be determined in several ways. pH meters electronically measure the ion concentration, giving pH in a digital readout. pH indicators are substances obtained from plant material that change color depending on the degree of acid or base of the substance it is mixed with. A few drops of indicator is added to a solution of the substance to be measured. The color the indicator changes to is matched to a color chart which matches the color of the indicator to the corresponding pH. Some indicators have a wide range of color changes from acid to base. Others are specific to a small range with in the pH scale, say 2.5 to 5.0 pH. Red cabbage juice is a common indicator you might be familiar with. Red cabbage juice has a color range from bright pink for a strong acid to yellow for a strong base. Other indicators, such as litmus, indicate if a substance is acid or base, not the degree of acid or base.
Indicators can be soaked into papers, making indicator paper for specific pH ranges. Indicator papers can be dipped into substances, matching the color change of the paper to a pH color chart for the indicator.
pH can be determined in several ways. pH meters electronically measure the ion concentration, giving pH in a digital readout. pH indicators are substances obtained from plant material that change color depending on the degree of acid or base of the substance it is mixed with. A few drops of indicator is added to a solution of the substance to be measured. The color the indicator changes to is matched to a color chart which matches the color of the indicator to the corresponding pH. Some indicators have a wide range of color changes from acid to base. Others are specific to a small range with in the pH scale, say 2.5 to 5.0 pH. Red cabbage juice is a common indicator you might be familiar with. Red cabbage juice has a color range from bright pink for a strong acid to yellow for a strong base. Other indicators, such as litmus, indicate if a substance is acid or base, not the degree of acid or base.
Indicators can be soaked into papers, making indicator paper for specific pH ranges. Indicator papers can be dipped into substances, matching the color change of the paper to a pH color chart for the indicator.
pH Values
| pH value | times acidity or alkalinity exceeds that of pure water (7.0) |
|---|---|
| Acidic 0 | 10,000,000 |
| 1 | 1,000,000 |
| 2 | 100,000 |
| 3 | 10,000 |
| 4 | 1,000 |
| 5 | 100 |
| 6 | 10 |
| Neutral 7 | 1 |
| 8 | 10 |
| 9 | 100 |
| 10 | 1,000 |
| 11 | 10,000 |
| 12 | 100,000 |
| 13 | 1,000,000 |
| Alkaline 14 | 10,000,000 |
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