Liquids & Solutions

What is a solution?

A mixture where a solute has been dissolved in a solvent.

What is a concentration?

A measure of how much solute is dissolved in a solution.

What is turbidity?

A measure of how cloudy a solution is due to particles suspended in it. (e.g. cells in culture)

What are the two types of dilutions you can find?

Linear dilution and log dilution.

What is a linear dilution?

Dilutions that differ by an equal interval.

e.g. 0.1, 0.2, 0.3, etc.

What is a log dilution?

Dilutions that differ by a constant proportion.

e.g. 10^-1,10^-2,10^-3, etc.

How can a serial dilution of a stock dilution allow for a solution of an unknown concentration to be determined?

A calibration curve / line can be plotted using the known concentrations of the stock solution.

What is a pH buffer?

A pH buffer solution is one that resists changes in pH when small quantities of an acid or an alkali are added to it, allowing the pH of a reaction mixture to be kept constant.

Why is a pH buffer used?

Many organisms / biological molecules are sensitive to changes in pH.

What does a colorimeter measure?

How much light is absorbed by a solution.

How can a colorimeter measure concentration?

Some light is transmitted (passes through) and some is absorbed by the solution. Less light will be transmitted through a darker / more opaque solution so more will be absorbed, giving a higher absorbance reading. More light will be transmitted through a lighter / clearer solution so will be less absorbed, giving a lower absorbance reading.