Inorganic Chemistry and Properties of H2O

Lecture 2 and 3

The theory of Chemical Evolution

Life on earth is originated from simple compounds in the early atmosphere and ocean → combines from simple to larger more complex compounds

Electronegativity

• How strongly an atom pulls electrons toward it in a chemical
  bond.

• (More protons + closer to nucleus = more
  electronegative)

Carbon, Hydrogen, and Oxygen’s electronegativity

C=H both less than O

Differences in electronegativity between atoms

Equally Shared= non-polar covalent bonds

Unequally shared= Polar covalent bonds

What is the heart of chemical evolution?

Water

Why is water a great solvent?

its (polar) hydrogen bonds between water molecules

Define Solvent

the liquid in which a solute is dissolved to form a solution.

solvents influence in chemical evolution

Chemicals are more likely to come into contact with one another and react as solutes

Hydrogens bonds react with…

Hydrophilic molecules which dissolve, where nonpolar/hydrophobic molecules don’t.

what does it mean when saying water is cohesive and adhesive

Allows the properties result in ability of water to stick together, resist gravity, and move up

Define Cohesiveness

The attraction between like molecules

define Adhesive 

Attraction between unlike molecules

Example of waters cohesive and adhesive abilities

It results in water’s high surface tension –
resistance to increased surface area (by breaking)
Makes it act like an elastic membrane

In which state is water more dense 

As a liquid because of it containing no crystal lattice structure

Why is important for water to have a high capacity for absorbing energy?

allows water to stabilize temperature changes within it!
Molecules are “protected” from heat that would break them
apart.

What does it mean to have a high capacity for absorbing energy? specifically in water

-Hydrogen bonds must be broken before heat can be transferred and water
molecules move faster
• Results in high specific heat = amount of energy to raise the temperature
of 1 gram of the substance by 1 C
• Also results in high heat of vaporization

Water dissociates, meaning?

Water can act as an acid (giving away a proton) or as a base (accepting a proton). In either case, it is weak, meaning only a few water molecules dissociate

What is the pH of pure water

7 (neutral)

What is the importance of water dissociating?

Allows water to act as a buffer, or reduce the impact of acids and bases in changing the pH of solutions

pH changes influence what?

the structure and function of molecules

Oxidation

when an atom or molecule loses and electron

Reduction

when an atom or molecule gains an electron

Potential energy

stored energy=chemical energy= a molecules potential to forming stronger bonds ex) weak bonds=more PE

Kinetic energy

energy of motion

Thermal energy= kinetic energy of molecular motion

Energy

Capacity to do work or supply heat

First law of thermodynamics

Energy cannot be created or destroyed, only transferred and transformed

Endergonic/Endothermic reactions

Means a reaction absorbs/needs energy to occur

Exergonic/ Exothermic reactions

Reactions that release energy

How does entropy affect the universe?

Always increases, will proceed spontaneously (no external influence, such as added energy to the system) if increase in entropy, which occurs if either or both

How do scientists think life began?

Early Earth: Molecules were exposed to massive inputs of energy!
• Heat from cooling earth
• Electricity from lightning
• Radiation from the Sun
• Potential energy in
chemical bonds

Evidence of chemical evolution

Stanley Miller’s spark discharge experiment

Compounds produced from Miller’s experiment

With electrical discharges: build-up of hydrogen cyanide, formaldehyde, and some amino acids

Importance of carbon

• Most versatile atom on earth

• typically, the backbones of organic compounds

• molecules made of multiple carbon atoms can be very complex

Macromolecules

Proteins, nucleic acids, lipids, and carbohydrates

Define entropy

A lack of order or predictability; gradual decline into disorder

Condensation reactions

Monomer in, water out → polymerization occurs

Hydrolysis reaction

Water in, monomer out→ polymers can be broken 

Why does hydrolysis reactions occur more often than condensation reactions?

Although both occurs in equilibrium, condensation requires a greater number of monomers to push the reaction forward