Compounds An atomic bond is a force which joins atoms together to form a molecule H O Atomic bond Water H

How Atomic Bonds Work Electrons are responsible for atomic bonding. There are 3 ways electrons can interact to form bonds

Ionic Bonds: STRONG An atom loses 1 or more electrons, giving it a positive charge. Another atom gains the electron(s) and becomes negatively charged + & - ions attract. - + e- e- Cl e- Na e- e- e- e- e-

Covalent bonds: STRONG 2 atoms share a pair of electrons H H e- e-

Polar Covalent Bonds: STRONG In a polar bond, electrons are shared unevenly. Since electrons are negative, the atom that attracts electrons the most becomes a little negative, and the atom losing the electrons becomes a little positive.

Water is Special Property #1: Water resists changes in temperature & phase Demonstration High “Specific Heat Capacity” Related Property: high melting & boiling points

Related: High Melting & Boiling Points

Property 2: High Surface Tension, etc. Water’s high surface tension causes: Adhesion: Water sticking to other surfaces “Capillarity” Cohesion: Water sticking to Water

Property #3: Excellent Solvent Water is very good at dissolving substances, particularly polar or ionic ones. “Universal Solvent”

Property #4: Density Anomaly Ice floats on water! Water is one of the only compounds known that gets less dense when it freezes!

Water is a polar molecule. The O-H bonds are polar covalent Molecules with positive and negative parts are called polar molecules. Polar molecules can form hydrogen bonds

New Bond - Hydrogen Bond: Pathetically WEAK! A Hydrogen bond is a weak bond between 2 electrical poles (usually different molecules)

WHY WATER HAS SPECIAL PROPERTIES Water has all of those weird properties happen because of 1 simple thing… HYDROGEN BONDS

Water is a polar molecule It has a positive and negative side, causing hydrogen bonds

How H-bonds Give Water it’s Special Properties Property How H-Bonds Make it Happen Temperature & Phase Stability Energy is required to break H-bonds, reducing the amount of energy for T increase or phase change Surface Tension, etc. Can form H-bonds with itself or other substances, making it “sticky” Solvent Areas of charge arrange around charged parts of molecules Density Anomaly H-bond length increases as temperature drops from 4oC to 0oC