PROPERTIES OF WATER Chapter 6.3 Water A water Molecules is made of Two Hydrogen atoms and an Oxygen atom H 2 0 O Polar Molecules Polar molecule unequal distribution of charges, have opposite charged regions. Polar molecules In each water molecule the oxygen attracts more than its fair share of electrons Oxygen acts negative Hydrogen acts Positive Water is neutral with a net charge of Zero Hydrogen bonds a weak interaction involving a hydrogen atom and a fluorine, oxygen, or nitrogen atom. Only one H-bond is weak but many are strong What are the properties of water Water is less dense as a solid Cohesion Adhesion Universal Solvent Water is less dense as a solid Water is Less Dense as a Solid Ice is less dense as a solid than as a liquid (ice floats) Liquid water has hydrogen bonds that are constantly being broken and reformed. Frozen water forms a crystal-like lattice whereby molecules are set at fixed distances. Which is ice and which is water? Water Ice Cohesion/Adhesion Cohesion: Water is attracted to water. Adhesion: Water is attracted to other substances Cohesion Cohesion is the attraction between particles of the same type Causes surface tension Adhesion Attraction between two different substances Capillary Action- Water molecules will tow each other along a narrow space Universal Solvent Water is called a universal Solvent because many things dissolve in it. Mixtures Water is usually part of mixtures A mixture is a combination of two or more substances in which each substance retains its individual characteristics Mixtures Heterogeneous mixtures the substance remain separated Example. Oil and water Homogenous Mixtures a uniform mixture Also called a solution Example. Salt dissolved in water Solubility Waters polarity and hydrogen bonds make it a good Solvent something that dissolves other substances. Solute the substance that is dissolved in the solvent. Detergents Detergents work by disrupting the adhesion and cohesion of water. Colloids Substances that dont dissolve but also dont settle. Water keeps the pieces suspended Acids and Bases Acids substances that release hydrogen ions (H + ) when dissolved in water. Bases substances that release hydroxide ions (OH - ) when dissolved in water. pH a measure of how much H + is in a solution. pH For every 550 million water molecules one naturally dissociates into a Hydrogen ion (H + ) and a Hydroxide ion (OH - ) H 2 0 H + + OH - Acid Base The pH scale Indicates the number of H + ions. Ranges from is neutral 0-7 is acid 7-14 is basic Each pH unit represent a 10X increase pH 3 is 10X10=100 time stronger than pH 5 The pH scale Buffers Buffers are weak acids or basis that prevent sharp changes in pH Neutralization! Produced by the body to maintain homeostasis Weak acid Weak base