Balancing Chemical Equations

In chemical reactions, sets
of compounds interact with each other to form new compounds. Chemists use equations to describe these interactions. Like mathematical equations, chemical equations conform to a set of rules. This allows equations to provide detailed information about a reaction.
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Covalent Bond Energy

Eating, putting gas in a car and throwing a log on a campfire all involve adding energy to a system. In each case, the energy is added in the form of covalent bonds that hold atoms together in molecules.

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pH

The definition of pH is straightforward: pH describes the concentration (or activity) of positively charged hydrogen ions (H⁺) in a solution. Underlying this definition is a set concepts that can be challenging to understand. The challenge comes from needing to appreciate:

Serial Dilutions

***UPDATE- View the updated illustration at SciencePrimer.com

Many modern biology and chemistry laboratory procedures require compounds to be mixed or dissolved in a liquid such as water.  These mixtures are called solutions.  Solutions have two components: a solute and a solvent.  Solutes are the suspended or dissolved material and the liquid is the solvent.  The amount of solute present in a particular volume of water or other solvent is called its concentration. For chemicals, common concentration units include weight/volume percent, weight percent, molarity and normality.  For biologically active compounds such as antibodies or enzymes, concentrations are often described using activity units/ml.  Concentration of bacterial and cell cultures are often reported in cells / ml or CFU (colony forming units)/ml.