Compare/contrast cohesion and adhesion. Bell work 9/10 Compare/contrast cohesion and adhesion.

What is the difference between an experiment and a demonstration? Bell work 9/10 What is the difference between an experiment and a demonstration?

Properties of Water

Water is Polar Polar molecule: a molecule with an unequal distribution of charges Results in a partial positive and partial negative charge, each on different ends of the molecule With what type of bond do we see polar molecules? Why? Covalent bonds. Polar molecules are a result of unequal sharing and therefore only occur in molecules where electrons are shared.

Structure of Water

Covalent Polar Bond in Water

Hydrogen Bonds in Water The attractions between two partially charged polar ends of water molecules are called hydrogen bonds. Weak electrostatic attraction between a hydrogen atoms and either an oxygen, fluorine, or nitrogen atom.

Hydrogen Bonds

Hydrogen Bonds Cont. Each oxygen will have a hydrogen bond with two hydrogen, and each hydrogen will have a bond with one oxygen How are hydrogen bonds different from van der Waals forces? They aren’t. Hydrogen bonds are a strong type of van der Waals force.

Mixtures Mixture: a combination of two or more substances in which each substance retains its original properties.

Homogenous Mixtures Also called solutions A mixture with uniform composition Contains: Solvent: the substance that another substance is dissolved in Solute: The substance dissolved in the solute. Ex: Kool-Aid and water, Kool-Aid is the solute, water is the solvent

Heterogeneous Mixtures A mixture in which all parts are easily identifiable. Suspension: a heterogeneous mixture in which individual parts will settle out. Colloid: a heterogeneous mixture in which individual parts do not settle out.

Water as a solvent Water is a universal solvent Like attracts like Polar molecules are attracted to each other Many polar or ionic compounds can dissolve in water because of its polarity. Even hydrophobic (water-fearing) compounds can sometimes be dissolved by water.

Acids and Bases Acid: a substance which when added to water produces hydrogen ions [H+]. Base: a substance which when added to water produces hydroxide ions [OH-]. When water disassociates, it forms H+ and OH-. Acids provide a source for more H+ ions when dissolved in water. Bases provide a source for more OH-

pH and buffers pH is a way to measure the acidity or basicity of a solution. It is a measure of the H+ in a solution Scale ranges from 0-14 0-6: acid 8-14: base 7: neutral Water is pH neutral Buffers react with acidic or basic solutions to neutralize pH.

pH scale