Basic Chemical Bonding and Properties of Water

TEKS

Vocabulary Valence electron Cohesion Adhesion Polar/Polarity Hydrogen Bonding Hydrophilic Hydrophobic

Prerequisite Questions What is the chemical formula for water? What are the 3 states of water called? What happens to a chemical when moves from one state of matter to another? What can you state about two oppositely charged particles?

Periodic Table Trends

Octet Rule Atoms feel electrically more comfortable with a full outer valence shell

Salt as an example Sodium wants to give up its outer most valence because then it has a full “inner” shell. Chlorine wants to steal one more electron because then its shell is full

Lewis Dot We only need to look at the valence electrons because they are involved in bonding Na

Basic Bonding concepts Covalent bonds form between the sharing of valence electrons connecting different atoms.

4 Emergent Properties of Water Water has a molecularly attractive nature (Cohesive and Adhesive) Water has a high specific heat Water is less dense as a solid (ice) Water is the universal solvent

Water is a polar molecule The electrons in a water molecule spend more time around Oxygen then the two Hydrogens. That makes water’s oxygen slightly more negative and the hydrogens slightly more positive

Cohesion of Water molecules Because opposites attract, the hydrogens of one molecule attract to the oxygens of other water molecules. This attraction between water molecules is Cohesion.

Adhesion of Water molecules When water molecules are attracted to other polar, non-water, molecules it is called Adhesion.

Specific Heat of Water Water has a high specific heat. That means it can absorb a lot of energy before it changes states. It is good at regulating temperatures in organisms and ecosystems

Solid Water is Less Dense than liquid water Ice floats on liquid water

Universal Solvent Because water is POLAR it is very effective at grabbing other polar molecules and moving them around

Concept Mastery Questions Why does water stick to other molecules? Why doesn’t water mix with oils/lipids? What would happen to life on Earth is water was more dense as a solid? How does water aid in thermal regulation?

Practice Questions (optional)