BIO.A.2 The Chemical Basis for Life
Topic Summary for Water Chemistry:
Water molecules (H2O) are polar because of an uneven distribution of electrons, creating a slight negative (–) charge in the oxygen atom and a slight positive (+) charge in each hydrogen atom. The attraction between a hydrogen atom of one water molecule and the oxygen atom of another water molecule is called a hydrogen bond.
Cohesion is an attraction between molecules of the same substance. It causes water molecules to be drawn together, producing surface tension
Adhesion is an attraction between molecules of different substances. It causes capillary action, an effect that causes water to rise in a narrow tube against the force of gravity.
A mixture is a material composed of two or more elements or compounds that are physically mixed together but not chemically combined. A solution is a mixture in which all the components are evenly spread out: the substance dissolved is the solute; the substance that causes the dissolving is the solvent. Mixtures of water and undissolved materials are suspensions.
A water molecule (H2O) can split apart to form a hydrogen ion (H+) and a hydroxide ion (OH–).
The pH scale measures the concentration of hydrogen ions in a solution. The scale ranges from 0 to 14. Pure water has a pH of 7.
An acid is any compound that forms H+ ions in solution. Acidic solutions have pH values below 7. A base is a compound that forms OH– ions in solution. Basic, or alkaline, solutions have pH values above 7.
Buffers are weak acids or bases that can react with strong acids or bases to prevent sudden changes in pH.
Topic Summary for Water Chemistry:
Water molecules (H2O) are polar because of an uneven distribution of electrons, creating a slight negative (–) charge in the oxygen atom and a slight positive (+) charge in each hydrogen atom. The attraction between a hydrogen atom of one water molecule and the oxygen atom of another water molecule is called a hydrogen bond.
Cohesion is an attraction between molecules of the same substance. It causes water molecules to be drawn together, producing surface tension
Adhesion is an attraction between molecules of different substances. It causes capillary action, an effect that causes water to rise in a narrow tube against the force of gravity.
A mixture is a material composed of two or more elements or compounds that are physically mixed together but not chemically combined. A solution is a mixture in which all the components are evenly spread out: the substance dissolved is the solute; the substance that causes the dissolving is the solvent. Mixtures of water and undissolved materials are suspensions.
A water molecule (H2O) can split apart to form a hydrogen ion (H+) and a hydroxide ion (OH–).
The pH scale measures the concentration of hydrogen ions in a solution. The scale ranges from 0 to 14. Pure water has a pH of 7.
An acid is any compound that forms H+ ions in solution. Acidic solutions have pH values below 7. A base is a compound that forms OH– ions in solution. Basic, or alkaline, solutions have pH values above 7.
Buffers are weak acids or bases that can react with strong acids or bases to prevent sudden changes in pH.