Educational Resources for Citizen Scientists

Terms & Definitions

Scientific Terminology

Conductivity:

A measurement of how well the water sample conducts electricity; the more dissolved metals in a solution, the higher the conductivity. The less dissolved metals in a solution, the lower the conductivity.

Water that is pure, or distilled, is a poor conductor of electricity. When salts, metals, and other inorganic materials dissolve in water, ions form. These chemical ions increase water's ability to conduct electricity. Some common ions include calcium (Ca²⁺), magnesium (Mg²⁺), and sodium chloride (NaCl₂). Organic compounds like alcohols, oils, and sugars do not have ions that conduct electricity. This measure of the amount of dissolved salts in water is called Salinity.

Aquatic organisms and plants are adapted to live within a certain range of salinity. Outside of that range, life has difficulty surviving.

Total Dissolved Solids (TDS):

A measure of the combined organic and inorganic content substances contained in a water sample. TDS gives a wider scale indication of the health of water sources.

Calibration:

The process of making sure the meter is returning accurate measurements. Meters should be calibrated every 2 to 3 uses.

pH:

The pH of water is a measure of its acidity or alkalinity. When we measure pH, we are measuring the concentration of hydrogen ions (H⁺) in the water. These measurements can be understood in the pH scale, which ranges from 0 to 14. A lower pH (0 - 6) indicates a high concentration of H⁺ ions and a more acidic water source. If a water source has a high pH (8.0 - 14.0) it is said to be basic, or alkaline, and contains much fewer H⁺ ions. On the pH scale, 7.0 indicates neutral pure water but having a pH of 7.0 is rare in nature.

Latitude:

A geographic coordinate that specifies the north-south position of a point on the Earth's surface.

Longitude:

A geographic coordinate that specifies the east-west position of a point on the Earth's surface.

Statistical Terminology

Mean (Average):

A measure of the "middle" or "typical" value; all the values are added and the sum is divided by the number of observations.

Standard Deviation

A measure of how far the data points are spread apart from the average. Data that are closely clustered around the average have a small standard deviation. Data that are spread sparsely from the average have a larger standard deviation.

Minimum

The smallest value that has been observed.

Maximum

The largest value that has been observed.

Median

A measure of the "middle" or "typical" value; it is the numerical value that separates the higher half of a data set from the lower half.

25th Percentile

25% of all the observations lies below this value. 75% of all observations lie above this value.

75th Percentile

75% of all the observations lies below this value. 25% of all observations lie above this value.

Replicate

A repeated measurement, performed as a check on the first measurement.