Properties of Water

Molecular Structure & Polarity

• Water is a "polar" molecule, meaning that there is an uneven distribution of electrons resulting in a molecule with a both a positively and negatively charged region. 

  • Water has a partial negative charge near the oxygen atom due the unshared pairs of electrons, and partial positive charges near the hydrogen atoms.

  • Definitions…

• Covalent Bond – when two atoms share one or more electrons

  • In a water molecule, each hydrogen atom is covalently bonded to the oxygen via a shared pair of electrons. 

• Hydrogen Bonds

• Hydrogen Bond – the electrostatic attraction between the partial positive charge near the hydrogen atoms and the partial negative charge near the oxygen atom on another water molecule

  • How one water molecule “sticks” to another

• Universal Solvent

• Water is called the "universal solvent" because it dissolves more substances than any other liquid. 

  • This means that wherever water goes, either through the ground or through our bodies, it takes along valuable chemicals, minerals, and nutrients.

SOLVENT

Definition = A substance that dissolves a solute to create a solution.

SOLUTE

Definition = A substance that is dissolved in a solvent to create a solution.

SOLUTION

• Definition = A mixture of two or more substances in which he molecules of the substances are evenly distributed

Density

• Ice floats because hydrogen bonds hold water molecules further apart in a solid than in a liquid.

  • Ice is less dense as a solid than a liquid.

• Heat Capacity

• Water has a HIGH heat capacity (it takes a lot of energy to raise its temperature) 

• WHY???

because the energy needs to first break the hydrogen bonds before it can raise the temperature of the water.

What is pH?

• pH is a measure of how acidic/basic a solution is. The range goes from 0 - 14, with 7 being neutral. pHs of less than 7 indicate acidity, whereas a pH of greater than 7 indicates a base. 

Surface tension: the property of a liquids surface to resist an external force by cohesive forces between liquid molecules

Cohesion: water molecules ticking to another due to hydrogen bonds

Adhesion: water molecules attracted to surfaces

capillary action: the movement of a liquid through narrow spaces due to the interplay of adhesion

polarity: the condition of having or being divided into distinct and opposite poles or characteristics