ps 100 Exam 3: Chemistry

Silicate Fibers, Sheets, and Chunks (see pictures on pg. 305-307)

o Asbestos- stringy o Mica-sheets/plates o Quartz-breaks apart randomly o Microscopic scale: Mica looks like a plate and asbestos looks like a point. The top view for asbestos will be thinner. o Be able to recognize them from these pictures (with the triangles) o The black lines in between are where it would break in the book pictures. Asbestos looks more like sandwiches.

Electronegativity

o Both ionization energy and electron affinity (the energy gained wen an electron is added to a neutral atom) contribute to electronegativity. o Electronegativity increases from left to right across rows and decreases down columns of the Periodic table.

Electrical Potential Energy

potential energy due to the relative positions of charged particles

Polar Bond

sharing of electrons is not equal. Electronegativity of the atoms decides this. You are more electronegative the closer you are to the top right corner.

Polarity of Molecules

you can have polar bonds and not have a polar molecule. This is a molecule in which the electrons aren't shared equally. Sticky because it attracts an oppositely charged part of a molecule. This makes it harder to melt. Polar molecules dissolve in polar substances such as water.

Know about the articles

Moderator slows down the neutrons because only slow neutrons ware useful and will lead to a disintegration of the uranium atoms. Cooling mechanism allows us to cool down the reaction and control it. Article: nuclear power plants are safer than the media portrays them because coal plants produce more radiation. Figure out the evidences they give you of this. You don't need to memorize figures.

Microscopic Kinetic Energy

- Kinetic energy associated with atomic and molecular motions (also known as thermal energy).

Solution

- mixture containing two or more compounds, at least one of which is a liquid.

Ionic Bonding

1 metal and 1 nonmetal form this bond, creating a semiconductor. Strong. Gives/receives electrons. Ex. salt

System

A small piece of the world around which we mentally draw a box and upon which we focus our attention. It may be a beaker containing an ice cube and warm water or a refrigerator or a living organism.

Alloy

A solid solution of metals

Isotope

A version of an element which has the same amount of protons but has a different number of neutrons.

Half-Life

All isotopes have half-lives

Alpha Decay

Alpha particles leave the atom. Losing mass. Strong force

Law of Increasing Disorder*

Also known as 2nd Law of Thermodynamics Total entropy in the Universe always increases although it may decrease in the system. To make things more ordered, you have to do work, which gives off energy.

Properties of Metals

Atoms exist as ions, energy levels overlap, and high melting temperature.

Average Nucleon Mass

Average nucleon mass decreases as you move towards iron (through fusion or fission). So the reactants in both fission and fusion have more total mass than the products.

Fission

Combining 2 smaller nuclei to form a larger one. This is what current nuclear power (commercial energy) is based on. Fueled by any heavy element.

Non-Polar Bond

Electrons in the bond are shared equally.

Non-Polar Molecule

Electrons in the molecule are overall shared equally. Dissolve in non-polar substances.

Properties of Covalent Substances

Energy levels are widely spaced, electrons are localized, electrons are shared by just a few electrons, and has electron cloud (dispersion forces occur).

Surroundings

Everything outside what we have defined to be the system. EXAMPLE laboratory bench on which the beaker is set. The kitchen that houses the refrigerator. Petri dish on which the organism is growing.

Balancing Chemical Equations

For a covalent reaction, balancing a chemical equation requires both sides to be equal. Don't forget diatomic particles!! Ex. 2 Hydrogen molecules react with one oxygen molecule, which will make two water molecules. For an ionic reaction, balancing a chemical equation requires keeping in mind how many electrons it has and thus what charge it has. Make sure you right that down. THEN you can add coefficients and balance it. Cross the charges if you don't have a one to one ratio

Ranking of Energy Forms (most ordered to least ordered)*

Gravitational Potential Energy and Macroscopic Kinetic Energy Nuclear Potential Energy Electrical Potential Energy (household) Chemical Potential Energy Thermal Energy (Microscopic Kinetic Energy)

Diatomic Particles

Have No Fear Of Ice Cold Beer Hydrogen Nitrogen Fluorine Oxygen Iodine Carbon Bromine Diatomic particles have a hard time dissolving in water.

Trans Fats

Have an artificial double bond structure, but they are straight. This makes them solid at room temperature and thus not good for you. They may even be worse for you than saturated fatty acids. They were created to increase shelf life of unsaturated fatty acids.

Unsaturated Fatty Acids

Have kink, so liquid. Can't clog your arteries easily, so is pretty healthy. Kinks are caused by double bonds. Makes ice because it's a covalent bond.

Radioactive Decays

Radioactive Decay: spontaneous disintegration of an unstable nucleus accompanied by the emission of ionizing radiation

Intermolecular Forces

in-between molecules (NOT atoms). Generally weak (easy to melt or boil), • 3 bonds in order of decreasing strength: o Hydrogen bonds o Dipole-Dipole bond o Dispersion (Van der Waals) Forces

Irreversible Process

increases the total amount of disorder in the Universe

Endothermic

is going to be COLD, take in energy

Exothermic

is going to be HOT, give off energy

Macroscopic Kinetic Energy

kinetic energy possessed by moving objects given by 1/2mass x (speed)2 EXAMPLE water molecules going over Niagara Falls

Bonding Molecular Orbitals

molecular orbitals that have high electron probability between atomic nuclei in a molecule. o When bonding molecular orbitals are occupied by electrons, the high electron density between the nuclei helps hold the nuclei together, contributing to a bond between the atoms. Has one cloud of probability

Anti-Bonding Molecular Orbitals

molecular orbitals that have low or no electron probability between atomic nuclei in a molecule and high electron density in areas not between the nuclei. o When anti-bonding orbitals are occupied by electrons, the resulting electron density in the anti-bonding orbital helps pull the nuclei apart, weakening any chemical bond that may exist between them. Has multiple clouds of probability

Beta Decay

electron (Beta particle) leaves the atom. Changing atomic number by converting electron to proton, etc. Weak force b/c is a proton turning into an electron, an electron turning into a proton, or a nucleus absorbing an electron.

Energy Diagrams

If end is below the line, it's exothermic and increases entropy. If end is above the line, it's endothermic and increases order.

Bands

In metals, the bands associated with bonding and anti-bonding orbitals overlap, forming one continuous set of levels. In semiconductors, the bonding and anti-bonding orbitals form distinct, separated bands.

Instrumental techniques

Infrared Absorption Spectroscopy Mass Spectrscopy

LEDs

LEDs are semiconductors When an electron jumps down across a band gap, it emits light (such as the red of an LED) from the band gap. If it gets warmer, the band gap will get smaller and thus the color of light will be one with less energy. Cool it down for a bigger band gap. Red hot (when the LED light gets warmer, the light will get closer to the red end, lower energy), blue cold (when it gets colder, the light will get closer to the blue end, higher energy)

Mixture

Matter that contains multiple substances. Many mixtures can be physically separated into their pure components.

Element

Matter that contains only one kind of atom o may be joined together--all listed on the periodic table

Compound

Matter that contains two or more atoms in a fixed, definite proportion. New compounds form when the relative proportions of atoms change

Saturated Fatty Acids

No kink, so straight and solid. Can clog your arteries, so isn't healthy. Usually has few double bonds.

Covalent Bonding

Not very strong-Dispersion Forces. Share electrons. Key terms: "molecule, polar, electron cloud, and share electrons."

Atomic Number

Number of protons in a nucleus

Name the 5 Types of Matter

Pure substance Element Compound Mixture Solution

Dipole-Dipole Bond***

Second strongest intermolecular force. Doesn't have to be between the H and O.

Properties of Ionic Compounds

Sometimes dissolve in polar substances. Atoms exist as ions, energy levels are widely spaced, high melting and boiling point.

Fusion

Splitting a large nuclei into two smaller ones. Occurs on the sun. Primary process in nuclear weapons. Fuel for it is plentiful on earth.

The Nuclear Forces

Strong and weak. Have small ranges.

Metallic Bonding

Strong. Share electrons. Key terms "sharing electrons, sea of electrons, and many electrons."

Hydrogen Bonds

Strongest of the Intermolecular forces. Has to be between H and F, O, or N. as a part of a water molecule. A type of Dipole-Dipole Bond.

Network or Extending-Bonding Substances

Substances in which every atom or ion interacts strongly with many neighbors.Network of linked atoms or ions form. distinct molecules or ion pairs don't exist in these materials.

Universe

System + Surroundings

Chemical Bond

The attractive force between nuclei and electrons that hold atoms together in molecules or atoms and ions together in network substances

Band Gap

The energy spacing between the semiconductor bands is called the band gap. Semiconductors tend to absorb photons whose energy matches or exceeds the band gap energy.

Valence Band

The lower energy band where valence electrons reside; is completely filed. When the temp is raised, electrons gain enough thermal energy to jump to the upper, conduction band.

Mass Number

Total number of protons and neutrons (superscript on left of number)

IR Spectra (see wks)

What do the lines on the graph represent? The different bonds in the molecule. Stronger bonds vibrate at higher frequencies, so the farther to the left is the stronger the bond is.

Metals vs. Semiconductors

When temp increases, semiconductors conduct more and metals conduct less.

Doping

When you put a little of another substance into an element in order to give it an intermediate step so that electrons can jump the band gap (thus causing conductivity).

Anions

atoms, or groups of atoms bound together, that have a net negative charge.

Cations

atoms, or groups of atoms bound together, that have a net positive charge.

Pure Substance

chemical matter that has a defined, unchanging chemical composition o defined, fixed chemical composition

Reversible Process

does not change the total amount of disorder in the Universe

Explanation of Metal Properties from Bonding Mechanism

• Explaining opacity (and shininess) using energy bands: The energy band is filled with energy levels. So when light comes along, it is easily absorbed into high energy levels. It spits the light back out, which is why metals are shiny. Malleability: fluid-like electrons shared between the nuclei act as a lubricant between the layers of nuclei. They reduce the repulsive forces that would be generated when layers of nuclei, sliding over one another, come into direct contact. High MP: electrostatic attraction b/t mobile electrons = strong forces that glue metal nuclei together = takes a lot of kinetic energy to pull them apart.

Explanation of Ionic Properties from Bonding Mechanism

• High melting and boiling point: Electrostatic forces that hold ions together are long-range. A great deal of thermal energy is required to pull individual ions away from their neighbors, which means high melting temperatures. •Electrical conductivity requires mobile charge carriers.

Dispersion (Van der Walls) Forces

• More dispersion forces = stronger. So longer monounsaturated ones are harder to rip apart than polyunsaturated because monounsaturated fats are easier to pack. • The more kinky = harder to pack and thus fewer dispersion forces

Application of Energy Form Ranking to specific processes (refrigerator, fuel engine)

• The energy of the universe always increases. There is heat behind the fridge even though it is colder inside (and thus more ordered). If you open the fridge, it will have to work harder, which will overall increase the temperature of the room because opening the door has increased the disorder in the fridge.

Infrared Absorption

• The pattern of absorptions or emissions of atoms and molecules can be used to identify a substance.

Chemical Bonding

• When 2 atoms are brought close together, the 2 positively charged nuclei attract the atomic electrons and create new different-shaped orbitals. • Molecular Orbitals: These standing wave shapes and sizes are different from those for individual atoms because of the multiple atomic nuclei. • If the electrons from the 2 atoms can achieve a lower energy arrangement in the molecular orbitals than in the atomic orbitals, the more stable arrangement will occur and the 2 atoms will stick or "bond" together. • Molecular orbitals are more complex than atomic orbitals and tend to be different for every combination of atoms. o They don't follow the same simple patterns as atomic orbitals.