LABORATORY EXERCISE 3: Introduction to Standard Curves

Flashcards covering key vocabulary from the laboratory exercise on spectrophotometers and standard curves.

Spectrophotometer

A laboratory instrument routinely used by biologists and other scientists to measure the concentration of a molecule in a solution, often by detecting how much light passes through the liquid.

Standard Solution

A solution containing a substance of known concentration.

Standard Curve

A set of data, most often an XY graph, that illustrates the linear relationship between the amount of a substance (X) and a particular measurement (Y), used to determine unknown concentrations.

Absorbance (Optical Density or OD)

A unit of measurement in spectrophotometry that is directly proportional to the molecule concentration in a solution, representing how much light is blocked from passing through.

Standard Deviation (SD)

A basic statistic used to calculate how much individual values deviate away from the replicate mean in a set of repeated measurements, indicating the precision of data.

SpectroVis Plus

A specific model of spectrophotometer made by Vernier™.

Cuvette

A plastic container used to hold a colored sample in a spectrophotometer for light measurement.

Absorption Maximum

The specific wavelength at which a colored substance absorbs light most strongly.

Methylene Blue

A dye used in this exercise, which absorbs light energy due to an electron shifting position to a higher energy-level orbital.

Stock Solution

A concentrated initial solution from which dilutions of known concentrations (standards) are prepared.

Standards

Known concentrations of a substance (e.g., methylene blue dye) prepared to create a standard curve.

Triplicate

A method of preparing each sample three times to check the precision of pipetting and measurements.

Precision

A measure of how close repeated measurements are to each other.

Calibration

The process of preparing a spectrophotometer, often involving a control solvent like water, to ensure accurate measurements.

Outlier

An individual data point that differs significantly (e.g., by more than two standard deviation units) from the group mean value, potentially indicating a less valid estimate.