Module 2 - Basic Chemistry, Water, pH Matter, Mass, and the Atom

Matter

•  Anything that takes up space and has mass.

Mass

• measure of the quantity of matter in a given object.

  • Volume and density.

 Democritus (400 BCE):

• atoms are indivisible.

  • Cannot be broken down further.

Atoms:

• the fundamental unit of matter

Protons:

• component of the atom’s nucleus with a positive electrical charge.

  • Elements are defined by the number of protons.

Neutrons

•  component of the atom’s nucleus with no charge.

  • Isotopes are defined by number of neutrons

Electrons

• component of the atom’s nucleus with no charge.

  • Isotopes are defined by number of neutrons

    • located some distance from atom nucleus and has a negative electrical charge

What is an element? 

• A substance that can not be reduced to a more simple set of components through chemical processes.

  •  Elements are pure forms of chemicals consisting of a single type of atom

What are the four main elements that make up the human body? 

• Carbon

• Oxygen

• Nitrogen

• Hydrogen

  • make up 96% of human body mass

atomic number

• is the total number of protons in an atom's nucleus, dictating the element's identity. 

atomic mass

• is the weighted average mass of all naturally occurring isotopes of that element

What is an isotope? 

• a form of an element as defined by the number of neutrons contained in the nucleus.

Molecule

•  two or more atoms together.

  •  Ex. O 2

Compound

• two or more elements together

  •  Ex. H2O

Atomic number:

• number of protons in the atom’s nucleus.

  • Carbon = 6

  •  Different elements have different proton numbers in their nucleus.

 Element symbol:

• abbreviation of element’s name.

Atomic mass:

• combined mass of atom’s protons and neutrons.

  • Neutron = 1.

  • Proton = 0.99862349, 99.86% mass of neutrons.

  •  Electron = 0.00054386734, 0.054% mass of neutrons

What makes a stable atom? 

• a balanced nucleus and a full outer electron shell.

How many electrons are found in each electron shell (1st shell, 2nd shell, etc..).

•  Electrons (e- ) orbit the nucleus of the atom at different energy levels (shells).

•  Atoms with vacancies in their outermost (valence) electron shell are reactive, whereas atoms with full shells are passive

  • 1st shell = 2 e-

  • 2nd shell = 8 e-

  • 3rd shell = 8 e-

Types of Chemical Bonding

• Non-polar covalent bond

• Polar covalent bond

• Polarity
  Covalent bonding

Non-polar covalent bond:

• when a covalent bond results in a non-polar molecule.

  • Ex: Carbon dioxide = CO2

 Polar covalent bond:

• when a covalent bond results in a polar molecule

  • Ex: Water 

Polarity

• A difference in electrical charge on opposing ends of a molecule.

Covalent bonding:

• when two atoms share pairs of electrons

Types of Chemical Bonding

• Non-polar covalent bond:

•  Polar covalent bond:

• Polarity

• Covalent bonding:

• Ionic bonding:

• Cation

• Anion

• Hydrogen bonding

Ionic bonding:

• when one atom donates an electron to another atom, resulting ions become linked by attraction of opposing charges.

Cation:

• a positively charged ion.

  • Ex: Na+

Anion:

• a negatively charged ion.

  • Ex: Cl-

Hydrogen bonding:

• covalent bond between hydrogen atoms and an electronegative atom.

  • Bound by attraction of electrical charge.

  • Relatively weak bonds.

Polarity:

• A difference in electrical charge on opposing ends of a molecule.

Covalent bonding:

• when two atoms share pairs of electrons

 Polar covalent bond:

• when a covalent bond results in a polar molecule

  • Ex: Water 

Non-polar covalent bond:

• when a covalent bond results in a non-polar molecule.

  • Ex: Carbon dioxide = CO2

Summary of Molecule Bonding

Covalent bonding: a bond formed between two atoms that share electrons

•  Bond strength : strong.

 Ionic bonding: a compound that is formed by the attraction of two oppositely charged ions

•  Bond strength: strong.

 Hydrogen bonding: a bond formed between the slightly positively charged hydrogen atom and the slightly negatively charged region of another atom

• Bond strength: weak

How does an atom become an ion? 

•  Ion: a charged atom; the number of electrons does not equal the number of charges.

What is a polar molecule? 

• These molecules are hydrophilic (water-loving).

• Partial charges work to pull apart ions

Know the properties of water: The Universal Solvent:

• Water can dissolve more substances than any other liquid.

  • Solute: substance being dissolved to form a solution.

  • Solvent: substance that a solute is dissolved in to form a solution.

    • Aqueous solution = water is the solvent.

  • Solution: a liquid mixture of two or more substances.

    • The hydrogen bonds of water molecules pull other compounds apart 

Vaporization

• transformation from liquid to gas.

  • Fastest moving water molecules transform to a gaseous state.

Evaporative cooling

• Sweat helps release internal body heat.

• cooling of surface when liquid evaporates.

Hydrophilic (“water loving”):

• compounds that will interact with water.

  •  Ex. Sodium Chloride (NaCl).

Hydrophobic (“water fearing”):

• compounds that do not interact with water.

  • Ex: Hydrocarbons (petroleum, oil) and lipids (fats).

  •  Hydrophobic molecules help contain water

Cohesion

•  the tendency for like molecules to cling together due to attractive forces

Surface tension:

• Water molecules are less attracted to air relative to each other and pack more tightly at interface

Acid:

• substance that donates hydrogen ions in an aqueous solution.

  •  Hydrogen ion = lone proton H +

Base:

• substance that accepts hydrogen ions in an aqueous solution.

  • Hydroxide ion = Oxygen and Hydrogen OH -

  • Alkaline = basic solution

Buffers:

• substances that mitigate changes in pH

Where are acids and bases found on the pH scale? (Ex: is a solution with a pH of 12 an acidic solution or a basic solution?)