Water and Acid/Base Relationships Unit 4: Biochemistry

The structure of an individual water molecule Water = H2O (That’s two hydrogen atoms and one oxygen atom) Notice the bent shape of the water molecule, and remember that oxygen is a bully, that unfairly shares electrons with the two hydrogens. This unequal sharing is called polarity. What else has polarity, or poles?

How water forms hydrogen bonds with other water molecules Notice how the partially positive end (hydrogen) is attracted to the partially negative end (oxygen). These water molecules are like two magnets coming together

How water forms hydrogen bonds with other water molecules Here are multiple water molecules bonding

How water bonds with other water molecules Remember that the magenta bonds shown here are like magnets, they are not chemical bonds.

Properties of water that are essential for life Cohesion: when water molecules are attracted to each other. We saw this in the previous slides. Adhesion: when water molecules are attracted to other objects. Remember that water is polar, and is only attracted to other polar molecules, never oil or fats, non-polar molecules. Cohesion/adhesio n is the driving force in water molecules being carries up and through a plant

Properties of water that are essential for life Capillary action: The combination of adhesion and cohesion in a very thin tube allows water to travel upwards. Capillary action is essential for plants in gaining water, but is not the only driving force in allowing water to travel up plants with tall stems, such as trees.

Properties of water that are essential for life Density: mass per volume. Most solids are more dense than their liquid counterparts, but not water. Ice is less dense than water, so it floats. This is important for the survival of some aquatic life during the winter, and serves as shelter in the arctic.

Properties of water that are essential for life Solvent versatility: since water is one of the smallest polar substances known, it has the ability to dissolve all other polar substances easily, which is why it is called a universal solvent. The water in our body is there to dissolve nutrients so that cells can use them.

The difference between solvents and solutes Solvent: the greater component of a solution Solute: the lesser component of a solution

The differences between solvents and solutes Concentration: how much solute is dissolved in a certain amount of solvent Aqueous: a term used to describe any solute dissolved in water Which solution is more concentrated?