Presentation on theme: "The Chemical Context of Life. Matter consists of chemical elements in pure form and in combinations called compounds Organisms are composed of matter."— Presentation transcript:
Fig. 2-13 – – ++ ++ H H O H2OH2O In a nonpolar covalent bond, the atoms share the electron equally In a polar covalent bond, one atom is more electronegative, and the atoms do not share the electron equally (casuing partial charges)
NaCl Na Cl Na Sodium atom Chlorine atom Cl Na + Sodium ion (a cation) Cl – Chloride ion (an anion) Sodium chloride (NaCl) - A cation is a positively charged ion (giving up) - An anion is a negatively charged ion (receiving) Animation: Ionic/Covalent Bonds Animation: Ionic/Covalent Bonds
Chemical reactions make and break chemical bonds Chemical reactions are the making and breaking of chemical bonds The starting molecules of a chemical reaction are called reactants The final molecules of a chemical reaction are called products 2 H 2 O2O2 2 H 2 O Reactants Reaction Products
Properties of Water Cohesion: binding together of like molecules, often by hydrogen bonds. Adhesion: the attraction between different kinds of molecules Surface tension: related to cohesion, a measure of how difficult it is to stretch or break the surface of a liquid.
Solvent vs. Solute Solvent: dissolving agent (doing the dissolving) Solute: substance that is being dissolved Aqueous solution: water is the solvent
Types of solutions: Hydrophilic: an affinity for water. “water loving”. Colloid: a large molecule that remains suspended and does not dissolve Hydrophobic: repel water, “water fearing”
Acids and Bases Base: substance that reduces the hydrogen ion concentration. Solution with more OH- than H+ pH between 9-14 Acid: increases the hydrogen ion concentration of a solution. Solution will have more H+ than OH- pH between 1-5 Neutral = H+ = OH-
Buffers: minimize changes in the concentration of H+ and OH- in a solution. Body internally maintains your pH at a neutral level.