Physical Science Unit 3

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Law of Increasing Disorder

Chaos is inevitable

Entropy loves

Irreversability

1 reversible situation: beaker full of water at 0* celcius (goes back from frozen to melted over and over again)

Entropy Equation

Chaos of Universe = Chaos of the system + Chaos of the surroundings

The 2nd Law of Thermodynamics (Law of Increasing Disorder) places limits on the efficiency of energy conversion. Which of the following is allowed?

 100% conversion of electricity to ambient temperature thermal energy.

Mass Spectrometer

Sort molecule pieces so they can see what molecules are in what sample

The structural organization of salts and metals.

Extended or network substances

The structural organization of Group 8A elements.

Atomic matter

The structural organization of water.

Molecular substances

The geometry around a carbon atom with four single bonds.

Tetrahedron

The geometry around a carbon atom with a triple bond.

Linear

Compounds containing transition metals are often brightly colored.

True

Sodium chloride (NaCl) and Magnesium (Mg) are examples of network substances.

True

Molecular substances melt at very high temperatures.

False (melt at very low temperatures because of weak bonds)

In a chemical formula, subscripts are placed to the left of the chemical symbol to indicate the number of that type of atoms in a molecule

False (to the right)

Mass spectrometry provides information about the energy associated with motions within molecules.

False, shows mass and frequency

Which is the best definition of an alloy?

Solid Mixture of metals

The point in a chemical reaction in which the forward and reverse reaction rates are equal.

Equilibrium

The low energy orbital of the pair of molecular orbitals (MO's) formed when two atomic orbitals combine.

Bonding Orbital

The high energy orbital of the pair of MO's formed when two atomic orbitals combine.

Antibonding Orbital

A temporary product of a chemical reaction that typically has more chemical potential energy than either the reactants or the final products.

Transition State

The energy that must be put into a system before a reaction can take place.

Activation Energy

A very fast reaction has a very high activation energy.

False

Four Properties of Metallic Bonds

1. Maleable

2. Conductors

3. Shiny / Opaque

4. High melting + boiling points (have to break bonds)

Metallic Bonds

Network solid

Resisitivity

The hotter metals get, the worse they are at conducting. Its the opposite for semi-metals

A measure for how difficult it is to make a current move through a substance.

Resisitivty

Metal-metal compound.

Alloy

Property of absorbing photons throughout the electromagnetic spectrum.

Opacity

A set of molecular orbitals so tightly spaced that the energies overlap each other.

Conduction band

Light can only be seen through metal that is so thin it is only a few atoms thick.

False (Metals absorb/ reflect light)

Metals are most likely to form alloys of all compositions when they have:

• Similar atomic sizes

• Similar crystal structures

• Similar chemical properties

Compounds between two different metals are called

Fusions

Ionic Bonds

Takes electrons without giving anything

Ionic Bonds Properties

Brittleness (moves like charges together so it shatters)
Low electrical conductivity (because electrons are locked, no non-local)
Ionic conductors
Transparent

Ionic materials form when

A metal and nonmetal come together

What happens when NaCl come together?

Na gives Cl an electron

NA + CL -

They cancel each other’s charge, never just one, always lots.

Ionic compounds have extremely low melting temperatures.

False

Covalence

Shares electrons in pairs, super strong

Dipole-Dipole interactions

Oppositely charges pulls stick together (the dipole sticks to the dipole)

Hydrogen Bonds

Stronger than dipole-dipole (Hydrogen bound to F,O,N)

Dispersion Force Interaction

Weakest of the interactions

Polar molecules

A molecule where there’s a dipole (one end is positive, one end is negative) like water

non-polar moleules

Neutral

Melting points based on polarity

Hydrogen Bonds, dipole-dipole, non-polar (strongest to weakest)

Physical properties of covalent materials

Non-conductive (no moving charges), transparent (widely spaced energy levels), low melting and boiling points

Ions composed of more than one covalently-bound atom.

Molecular Ions

Forces between molecules

Intermolecular

A covalent bond involving two pairs of electrons shared between the two bound atoms.

Double bond

Bonds or molecules having an unequal distribution of charge with one end being positive, the other negative.

Polar

The chemical bond between two non-metals characterized by sharing of valence electrons.

Covalent bond

Chemical compounds made up primarily of the elements carbon and hydrogen.

Hydrocarbons

A linear system that has a positive end and a negative end.

Dipole

A material in which another material dissolves.

Solvent

Having a pH value less than 7, meaning that the hydronium ion concentration is greater than in pure water.

Acidic

What is a “strong bond” based on?

How strong the bond is

How do you determine if the forces between molecules are strong?

NOT by the bonds, by the intermolecular forces. Higher boiling point → stronger force.

Saturated fats

• The carbons in the chain are totally saturated with hydrogens; they are holding all that they can (2 each)

  • The chains stack really nicely, so they are solid at room temperature

Unsaturated Fats

• Two carbons double bond to each other instead of hydrogens (kinks), so it’s not totally saturated with hydrogens

• One “kink”; monounsaturated fats

• two or more kinks, polyunsaturated fats

Hydrogenated Oils

• manufacturers pump a lot of hydrogens into the unsaturated fats to make them not have kinks and extend their shelf life

• Can form trans fats

What changes the melting point of a fatty acid?

How long the chain is and how many kinks it has

• Longer: higher melting point

• More kinks: lower melting point

Silicates

1. Asbestos (metal, breaks off in strings)

2. Mica (breaks off in plates)

3. Quartz (break off in chunks)

Building block of most rocks.

Silicates

Contains only C-C single bonds.

Saturated fatty acids

Contain C=C double bonds.

Unsaturated fatty acids

Silicate mineral in which all silicate tetrahedra are bonded with equal strength to four other tetrahedra.

Quartz

Best geometric arrangement of four bonds around a central atom.

Tetrahedron

State of matter in which atoms or ions are arranged in an orderly, repeating patterns.

Crystal

Nuclear fusion

two small atoms combine to make a larger atoms

The protons and neutrons combine, but get smaller (when large things combine it takes energy)

Nuclear fission

Larger atom splits apart to create two smaller atoms

Issue with nuclear power

Everything is splitting (fission) and when the mass goes down it increases the energy.

Alpha Decay

Loses a helium atom

• Mass: 4 (top number)

  • Atomic number: 2 (bottom number)

Beta Decay

Atomic number: increases by 1

1 electron is lost

Mass number does not change

Gamma Decay

No change