Monday, November 9th, 2009

Today we saw the topic “Chemical Balancing". Chemical Balancing is a way to balance an equation, and there are 3 methods but today we saw the Trial and error method also known as Inspection method.

We can ask first of all why we need to do it, well we need to follow the rule “matter can’t be created nor destroyed just transformed”.

To make a chemical balance first you need an equation:

Na + Cl → NaCl (It’s not balanced)

Then you need to write the amount of molecules of each element:

Na + Cl2 → NaCl

Na 1 Na 1

Cl 2 Cl 1

If you notice, the amount of Chlorine is not the same and we need to apply the rule of “matter can’t be created nor destroyed just transformed”. So we need to aggregate numbers to balance the equation:

Na + Cl2 → 2NaCl

Na 1 Na 2

Cl 2 Cl 2

Now we balanced Chlorine but now Sodium is not balanced, so we need to aggregate another number:

2Na + Cl2 → 2NaCl

Na 2 Na 2

Cl 2 Cl 2

Now the equation is balanced with the same amount of molecules before and after the arrow.

Michelle Torrero

Friday, November 6th, 2009

Today the class started with awful news: The test is on November 20^th!

So if anyone else was planning to go to the New Moon´s premier you need to come early to school, even if you´re sleepless.

So...

Today´s theme was Chemical formulas and equations

An equation can tell you the elements that you have, the cuantity and, in some cases, the state or compatibility.

A chemical formula is a concize way of expresiing information about the atom that constitute a particular chemical compound.

Every compund that exists has an specific formula.

There are some elements that don´t come alone. They come in pairs:

H2

O2

N2

F2

CL2

BR2

I2

There was another theme today: Types of chemical reactions.

All chemical reactions involve a change in substances and a change in energy. Neither matter or energy is created or destroyed in a chemical reaction, only changed.

There are four types:

SYNTHESIS REACTION
In a synthesis reaction two or more simple substances combine to form a more complex substance.

DECOMPOSITION REACTION
In a decomposition reaction a more complex substance breaks down into simpler parts. Synthesis and decomposition reactions are opposites.

SINGLE REPLACEMENT REACTION
In a single replacement reaction a single uncombined element replaces another in a compound.

DOUBLE REPLACEMENT REACTION
In a double replacement reaction parts of two compounds switch places to form two new compounds.

Erin Alice Gil

The homework was:

Find 3 examples of each type of reaction.

Friday October 30th 2009

On Friday's class we learned about Covalent Bonds.
A Covalent Bond its when atoms share a pair of electrons. The difference between this one and a Ionic Bond its that an ionic bond needs to lose or gain electrons and become positive or negative and covalent bonds just share (both have and use the electrons if they need it).
For example: H= that has 1 valence electron and needs just one to be stable -----> Both can form H2O by a covalent bond.
O= which has 6 valence electrons and needs 2 to be stable
A characteristic of covalent bonds its that are "Polar Molecules", that means that the atoms has more positive charge in one side and negative charge in the other. We can use water (H2O) as an example in this too.




It has positive charge in the Hydrogen side and and negative charge in tho Oxygen side because of the excess of electrons.
(the red one is Oxygen and the whites are Hydrogen.)















When all the class understood this we made an activity outside, we made a covalent and a ionic bond simulating to be atoms (neutrons, protons and electrons).

Laura Carrillo

Monday October 26th 2009

Today we talked about ionic bonds, but class started with a review of what makes up an atom. Which is the proton (positive), electron (negative), and neutron (neutral). Then he went on to tell us that each atom has the same number of neutrons, protons, and electrons, but that the mass is different; For this one is in a way the sum of the neutrons and protons (it is also the electrons but they barely make a difference so it is not very noticeable). Then we got to the actual subject IONIC BONDS.
To know what that is we need to understand what ions are: The elements that have charges, there are two types: Cations (positive) and Anions (negative).
Now to get there we need to discuss metals and nonmetals.
"Atoms of metals tend to lose their electron valances leaving a complete octect in the next energy level."
Which basically tells you that metals tend to give up electrons.
Example: Na (z=11) configuration= 1s²2s²2p⁶3s¹which means it has 1 valance electron, and in order to be like a noble gas it has to lose one electron by doing this the atom goes from neutral to positive because now it has more protons than electrons. So it becomes a cation of sodium, because when they become cations they don't change the name.
-When you look at the periodic table: the number in the top right corner with the negative and positive charge tells you how many electrons ot gives or takes away and whether it becomes a positive or negative charge.
You can also look at he columns (1a, 2a, 3a, etc.) to know how many it loses.

Once an atom becomes a cation or anion it becomes different than the original even if it's a small different it can cause a lot of changes.


"Atoms of nonmetals tend to gain electrons or to share electrons with another nonmetal to achive an octet."

(most not all)

example:Cl (z=17) configuration= 1s²2s²2p⁶3s²3p⁵so it needs one more electron to become a noble gas, and by gaining an electron it emds up having more electrons than protonsand is negative instead of neutral. There are some that become pseudo noble gas because they're not exactly a noble gas but they are stable.
When an atom becomes an anion you change the name by replacing the last syllable with -ide.
ex: Chlorine -> Chloride.

Now the best way to know if it loses or gains electrons is by looking at it's valance number:
if it's 1-3 it loses
if it's 5-7 it gains
if it's 4 then it's a metalloid and it can do either, lose or gain.

If you've paid attention you've realized that despite me saying we were going to talk about ionic bonds I have yet to say anything about them, that's because you need to know evrything I've just said before you understand what's next.
Ionic Bond is held together by electrostatic forces.
Metal cation + Nonmetal anion = Neutral compound
(+) (-) (±)

Ex:
Na (+1) + Cl (-1) = NaCl

(P.S. Cations always go first it would never be written ClNa)

That was the whole class, and there was no homework.

Victoria Bracamontes

Friday, october 16th, 2009

CLICK TO ENLARGE

Erin Alice Gil

Monday, October 5th, 2009

Today we saw a new theme: the periodic table.

First the teacher shows us a little bit of the past:

· 1860, only 60 elements were known.

· They knew only the basic stuff.

· Jöns Jakob Berzelius- made the 2 letter system for elements.

· Johann Döbereiner- was the 1^st to “organize” the periodic table by the Law of Triads (groups of 3 elements because of their property.)

· John Newlands- use the Law of Octaves (groups of 8 elements), and he relate it with music scales.

· Mendeleev- He was the real 1^st one who made a periodic table with 12 columns and 8 rows, also we left blank spaces – he predicts the properties of the missing elements. He was considered “Chemist of predictions.”

· Henry Moseley- he organized it by atomic numbers.

As well, teacher Ariel explained us the 2 letter system for elements, that is to use the first letter of the name in English; but also why some elements are not in that system, and that’s because some elements were first written in Latin and they kept that name like gold (Au) means Aurum in Latin, and after that, he gave us a list of the 5 elements in Latin:

*Aurum (Au) = Gold

*Kabium (K) = Potassium

*Natium (Na) = Sodium

*Ferrum (Fe) = Iron

*Argentums (Ag) = Silver

· Of all the elements, 83 elements are stable in nature, while 24 are not from earth.

Now, the periodical table is conformed of rows (horizontal) and columns (Vertical):

The horizontal are the Periods-the mass and size are similar in each period.

The vertical are the Groups, and in these one are different classification:

1) Alkali Metal

2) Alkali earth metal

11) Coinage Metal- soft metals (gold, silver and copper)

17) Halogens- they separate vey easy.

18) Zero, Noble gases, Inert gases- the ones that are stable.

· Periodical table also use the electronic configuration helping you find a element more quick; the periods will be used as the biggest number of the list, example: if you got as the biggest one 3p⁴, then the period will be #3; and the groups are represented in these way:

Andrea Favela

Fridat, october 2nd, 2009

Today at the beginning Mr. Ariel said that he wasn't going to ask who found the homework hard, because apparently most of us had sent him e-mails asking for help, and he wet on to explain how it should've been done. When he drew it, one of the students realized that he had forgotten to tell us something when it comes to drawing the electrons in their shell. We thought that we were just adding the next drawing of the levels when really we were supposed to have 2 "s" levels and then the first "p" leve, when most of us thought that we only draw the s level once and then the p and so on, so he made it clcear that we're suppossed to draw the "s" level once again as we get to a new level. Also he gave us a hand out that tells us the order of the electron configuration and said that that would help us understand how to place the electrons. It looked something like this, with arrows telling you to go diagonally down from right to left:

1s
2s 2p
3s 3p
4s 4p 4d
5s 5p 5d
6s 6p 6d 6f
7s 7p 7d 7f
Also it had a picture of Bohr's model of the atom and it had how many electrons could fit in each of the levels and the order of them. And he explained it as if it was a concert stadium with all the seats beong the same price. First you fill the front row tickest which aare 1s and 2s then you move on to the ones that get farther and farther away. We did a buch of execercises with them and the first 5 to finish one of them would get an extra point in the test. One of the questions was the electron configuration of Gold (79) which was:

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d⁹

And he left Platinum's electron configuration for homework.

Victoria Bracamontes

Monday,September 28th 2009.

Today we started talking about quantum numbers and since the beginning Mr. Ariel said that it would be confusing.
In a way they are what tells you where the electrons of a specific atom could be located.
Now there are 4 types of quantum numbers the first would be:
Principal (n):
What this one basically defines the energy levels it has and n=1,2,3, ... up to infinity, but it does HAVE to be a whole number. The bigger n the more energy it has and the farther away form the nucleus it is.
The next quantum number would be:
Angular momentum (l):
What this one does is basically give you the shape of the orbitals, it tells you what part of the energy level the electron is located in.
l=0,...,n-1
And what each number means is which orbital it has... Thinking back to last year they told us about the s, p, d, f orbitals and that's what the numbers stand for.
0=s which is just a sphere.
1=p it's often called a dumbbell and always comes in groups of 3.
2=d it's like 2 dumbbells put together.
3=f is more complex it's like 2 d orbitals put together.
And so on each orbital has a different shape.
YOU CAN HAVE MORE THAN 1 SUB-ORBITAL
an example would be that:
if n=5
l=0,1,2,3,4 and it would have the possibility of having all s,p,d,f orbitals, but it's not always necessarily using them all.
Next is the:
Magnetic number(ml):
This one determines the orientation of the sub-orbits and how many orbitals in a set. (the way it is turned and seen, and how many possible views it has).
ml=-l, 0, +l (it's an L not a one!)
so if l=0 then ml=0 and you'll only have one view, because no matter what way the spherical orbital is turned it will always look the same.
the next one is:
Spin number (ms):
It tells you the direction the electron is spinning.
it can only be +1/2 or -1/2.
It is like the elctronic configuration and the arrows, you always start with the positive (up arrow) and then put in the negative (down arrow).
It will always be 1/2 because it's the way it is, it will NOT change.
The example he showed us was of H (hydrogen), its quantum numbers would be:
n=1
l=0
ml=0
ms=+1/2

If you still had doubts he left two links of two videos on facebook which explain it and might help you grasp it better.
The homework for Friday was the quantum numbers for the following elements Berillium, Boron, Carbon, Nitrogen and Oxygen.

Victoria Bracamontes

Monday, september 21st, 2009

Today we started with the Unit 2.

This unit beggins with a theme that we already saw at the end of the last unit:

¨The atom¨.

Then the next theme in this unit is the ¨Periodic table¨ (OMG! Too much elements to memorize!).

The last theme is ¨Quantum numbers¨ (My head hurts!).

Anyway, back to ¨The atom¨.

The teacher started asking about the atomic model and the light spectrum, the last themes we saw.

After that he spoke a

bout the Light.

The light can be a wave or particles. Better said, it has particles but travels in waves.

The light particles are called Photons.

Then we started with

the waves properties and types.

Crest: Is the highest point in the wave.

Wave length: Is the distance between 2 crests.

Amplitude: Is the distance between a crest and the lowest point call

ed trough.

Electromagnetic Spectrum

Radio waves: Biggest waves. Like TV., AM or FM. 3Km. To 3cm.

Microwaves: From 30cm. To 0.3cm.

Infrared: About 3 micrometers. 1000 micrometers is 1 milimeter. Infrared is familiared with heat.

Visible light: 1 micrometer to 0.4 micrometers.

Ultraviolet: 0.3 micrometers to 4 nanometers.

X-rays: From 3 nanometers to 0.3 nanometers. Can go through almost everything.

Gamma rays: Smaller than 0.3 nanometers. They go through everything. They´re radioactive and cause you harm.

Well...that was the class. And for everyone that was there: The famous and so slippery name in english of ¨valle¨ is trough. :)♥

Erin Alice Gil

Friday, september 4th, 2009

Class started and the classroom was unusually empty, then as Mr. Ariel took attendance people started arriving. Then he started class and as he was warming up to the good stuff the remaining people arrived interrupting his explanation or introduction to the subject of that day which was Atomic Theories.
He started with a little diagram to explain how Aristotle thought that all matter consisted of four elements: Earth, Air, Water, and Fire. and these had 4 qualities: Dryness, wetness, coldness, and hotness.
Everyone believed that until Democritus improved his idea. Democritus believed atoms were indivisible (which was right), and he thought each different thing was made of different substances, not just the four elements. He foreshadowed that there were more elements and that they were indivisible. Then he split us up in groups by choosing 7 "team captains" and having them choose one by one their teams, then switching the captains to a team they didn't make. to explain the rest of the atomin theories.
First came Dalton's model. He said that elements have/composed of tiny indivisible particles called atoms. Also, that the atoms of the same element are identical in size, mass, and chemical properties, and they differ from atoms of different elements. Another thing he said was that all chemical reactions are changes in the proportions of atoms. (Which were all correct thoughts.)
Then in 1897 the Atom was observed for the first time in England. And with came the Electron and Thomson's model He discovered Electrodes: anodes are negative and catons are positive. He realized that electrons move very fast and have negative charges. Which is of 1.602x10^-10.
Radioactivity is a phenomenon where atoms decompose spontaneously. It was discovered accidentally by Henry Bequetel in 1892. Radioactive elements are polanium and radium. The different types of radiation are:
Alpha: Lowest penetrability
Beta:Moderate penetrability
Gamma: High Penetrability
Next was Rutherford's modela nd the Nucleus. Rutherford's theory was that protons and electrons were evenly dispersed. He made an experiment where they shot alpha particles througha thin sheet of gol foil. If he had been correct the particle should've gone straight thorugh unhindered, but since he was mistaken some defleted as they passed through and others bounced back. With that he came up with another atomic model:

In his model protons would be concentrated in a small space and the electrons would be orbiting the empty space around them, and the area where the protons where was called the neutron His model is often called the planetary model becaus of its resemblance to the planets orbiting the sun. The diameter of a typical atom is about 10,000 times greater than the diameter of a typical nucleus. So if the atom was the size of a football field the nucleus would only be the size of a grape.
Then came Bohr's Model. WHich was a proposed quantized shell model og the atom to explain how electrons can have stable orbits around the nucleus: The Quantum Model. It's principles are:
-An atom is composed by a very small nucleus which is a positive charge (Just like Rutherford's model)
-The electrons of an atom can only exist in "special" energetic shells or orbits around the nucleus and can have the names of 1. 2. 3 or K, L, M etc.
-The electrons have definite and characteristic energy according to the shell. K orbit has the lowest radio and energy because it is closest to the nucleus.
-Atoms have two energetic states: Ground state(Stable) and Excited state(too much energy).
When they are in the escited state they need to jump to the next orbit but by doing that they get tired and lose energy so they have to bounce back to their original orbit this movement is called a transition, and each jump has a characteristic light(emission spectrum) it gives out.


Then came Sommerfeld's model which was just Arnold Sommefeld's improved quantum model Saying that there was the same amount of protons and electrons, and that the shells could be circular or elliptical.
Then came the Modern Model which was established by Schrodinger and Dirac. It is a complex mathematical model. It is the result of integration of different knowledge. It sattes that electrons are distributed around the nucleus in probability regions called atomic orbitals. It is also called Quantum mechanical model. It was proposed because:
a. Albert Einstein explained the Photoelectric effect.
b. Louis De Broglie proposed that matter has a particle/wave duability.
c Werner Heinsberg proposed the Uncertainty Principle

And that was basically the whole class, just taking notes on the presentations. He did sat we should watch a video titled : "What the 'bleep' do we know?" to help understand it better.

Victoria Bracamontes

Monday, August 31st, 2009

First I want to say that teacher is kind of frustrating I don't know, is just my opinion, and I really needed to say it, I know students are too, but oh just anyways, that is just my opinion. And to say I was really paying attention
Let's talk about the real journal the thing that really matters, during last class we were talking about matter and its properties, It divides into General Properties and Specific properties.\

Matter Properties.

General Properties: They are common to all kinds of matter.

Volume: Space that matter occupies.
Mass: Ammount of matter contained in a body.
Inertia:Opposition that a body presents to change its movement or its static state.
Weight: Measure of force of attraction between objects due to gravity
Elasticity: When bodies can be temporarily deformed by an external force.
Impenetrability:Two bodies can't occupy tha same space at the same time.
Porosity: All bodies present spaces between particles.
Divisbility: All bodies can be decomposed by mechanical or energetical means.

Specific Properties: Helps to identify a substance from another one.
It can be divided into Physical and Chemical.

Physical property: It can be measured and observed without changing its composition or identy of a substance.

• Changes can be reversible.
• Nothing is used up.
• Nothing is formed.

Chemical properties: Refers to a characteristic that matter exhibits as it undergoes a change in its composition.

• One or more substances are consumed.
• One or more sibstances are formed.
• Energy is absorbed or released.

EXAMPLES.
Physical: State of matter, Odor, density, temprerature, melting point, boiling point.
Chemical: Reactivity, acidity, vapor pressure, solubility, thermal stability, oxidand strength, reductant strength.

Properties can also be classfied on the basics of whether they depend on how much of matter is present.

Extensive properties: Are dependamnt upon the ammount of substance present.
Example: Mass, Volume.

Intensive properties: Are independant of the ammount of matter.
Example: Color.

Okay, my opinion about this, classes are starting to be boring, I mean, I understood it, but if we always do the same it kinda make me feel sleepy or anything, anyways, this topic I think I understood it very well.

Energy.
It is the capacity to do a work.

Energy can be presented into two states:

Kinetic or movement energy: Energy of a body because of its movement.
Example: Waterfalls.
Potential or stored energy: Energy of a body because pf its position.
Example: Water stored in a dam.


Conservation Laws.
Matter conservation Law: Mass is neither created or destroyed, just transformed. -Antoine Lavoisier.
Energy conservation Law: Energy is neither created or destroyed, just transformed. -Robert Mayer.
Mass-Energy conservation Law: The ammount of mass-energy that is present in the universe is constant. -Albert Einstein.

Kabick Tam