Field Trip Success!

Today was our field trip to the great lakes science center!  We learned a lot and had a lot of fun.  But, now it's time to focus on this weeks lessons....

For Students:

How does wave-particle duality affect our model of the arrangement of electrons in atoms??  So far we have discussed the simplistic version of a model of an atom with a nucelus, composed of protons and nuetrons and electrons orbiting around it.  In Bohr's model of the atom, both the energy and location for the electrons in the atom can be described accurately.  But, this is merely a simple view of what the atom really looks like.  Werner Heisenberg and Max Born came up with the idea that, for something as tiny as an electron, and given that the electron has wave and particle properties, any attempt to determine accurately either the location or the energy will leave the other uncertain.  In other words, you can definately know an electrons location or it's energy, but not both at the same time.  This is now known as Heisenberg's uncertainty principle.

The importance of this idea is that we can asses only the likelihood or the probability of finding an electron with a given energy within a given region of space.  This is the basis of quantum mechanics... next time we will discuss quantum numbers and orbitals!

For Parents:

The field trip was a great success.

The great lakes science center is a great place for schools and families alike.  If you have not visited it, I would highly recommend it!



Introduction to Quantum Mechanics

For Students:
Answers to this weeks quiz are as follows:
1.  A frequency of 2.45 gigahertz has what wavelength in meters?
    (2.45 gigahertz = 2.45 x 10^9 Hertz)  c = wavelength x frequency,  wavelength = c/f
     = .122 m
2.  Which color in the visible spectrum has the highest frequency? = violet
3.  Which color in the visible spectrum has the highest wavelength = red
4.  Which is longer the wavelength of a microwave or a radio wave? = radio
5.  what is the speed of all electromagnetic radiation? = 3.00 x 10^8 m/s

Next we are going to be talking briefly on quantum mechanics and how it relates to chemistry.  We have already talked about how electrons and light both exhibit particle-wave duality.  They both can act like a wave or a particle, in certain circumstances. 

This man is Louis Victor de Broglie and he proposed that a free electron (not attached to any atom) with a mass m moving with a velocity v, should have an associated wavelength.  His equation, wavelength = h/mv is very usefull in many chemistry problems.  The h in this equation is a constant, called Planck's constant, and is named after Max Planck.  It's value is 6.626 x 10^-34 J/sec.  Remember that light and electrons behave like particles and waves, but not simultaneously.  In a given situation, they will behave like either a particle or a wave.  We will talk more about the de Broglie equation and wave-particle duality this week.

For Parents:

Wednesday is the big day!  Field trip day!  We are planning to see and do everything and we should have a lot of fun.  Make sure your child arrives to school on time on Wednesday as we will leave promptly at 8:30 am.  Also, be sure your child has a bagged lunch.  Thanks for all your help!



Shifting gears

Can you believe we are in the 6th week of school already?  It seems like we just started, but it sure is going fast.  Only 12 weeks left, and still so much to cover.  We are going to be leaving the subject of heat and energy for now, and we are moving on to a more in depth look at the structure of atoms....

The is the aurora borealis, or northern lights.  These beautifull colors are caused by electrons in the solar wind bumping into molecules in the upper atmosphere.  This make the molecules excited and they emit light. 
The colors seen can be white to red, green, orange, and others.  Different colors mean different things, like wavelenths (light travels in waves), energy, etc.

For Students:

Most of our understanding of atomic structure comes from a knowledge of how atoms interact with light and how excited atoms and molecules emit light .  In order to understand atomic structure, we will first look at electromagnetic radiation.  Electromagnetic radiation really is just waves of electric and magnetic fields working together.  In 1864 a man by the name of James Clerk Maxwell created a theory to describe these waves.  He proposed that electric fields produce magnetic fields and changing magnetic fields produce electric fields.  Two important properties of waves are its wavelength and its frequency.  A wavelength is symbolized by the greek letter lambda: and it is the distance between successive crests of a wave.  A frequency is symbolized by a lower case f and it is the number of cycles per second.  1 cycle per second is equal to a hertz. (Hz).  And finally, the speed of all electromagnetic waves (not just light) is 3.00x10^8.  Wavelength and frequency are related to a waves speed by this equation:

C (m/s) = lambda (m) x f(s^-1)

C = 

X Frequency

For Parents:

Thanks for your prompt attention to the permission slips.  Our field trip is next week!

Quiz results and more about energy!

For Students:
Hello!  Hopefully everyone's quiz this week went well.  The answers are as follows:
1.  How much energy must be transferred to raise the temperature of a cup of coffee (250 mL) from 20.5 C to 95.6 C.  Assume water and coffee have the same denisty and specific heat capacity (4.184 J/g*K)?
       change in T = 368.8 K - 293.7 K = 74.1 K
       q = C x m x (change in) T
       q = (4.184)(250)(75.1)
       q = 79,000 J or 79kJ

2.  An 88.5 g piece of iron whose temp. is 78.8 C is placed in a beaker containing 244 g of water at 18.8 C.  When thermal equilibrium is reached, what is the final temp.?
       q(metal) = q(water)
       (C (water) x m(water) x (change in temp.)) = (C(Fe) x m(Fe) x (change in temp.))
       (4.184 x 244 x (T(final) - 292K) = (.449 x 88.5 x (T(final) - 352K)
       T (final) = 295K or 22 C

The two above photos show two very important temperatures for water, and for other substances as well.  Everything has a melting and a boiling point.  The energy transferred as heat that is required to convert the substance from a sold at its melting point to a liquid is called the heat of fusion.  On the other hand, the energy transferred as a heat to convert a liquid at its boiling point to a vapor is called the heat of vaporization.  These values are constants for a particular substance and a table with some common values can be found in the back of your book.  It is important to recognize that the temperature remains the same throughout a change of state.  These types of situations will be discussed this week.

For Parents:
Hopefully everyone received their permission slip for our upcoming field trip to the Great Lakes Science Center.  Permission slips must be returned by Friday.  Remember, students will need a bagged lunch on the day of our trip.  Thanks and have a great week.!

Heating and Cooling in reactons

Happy Wednesday everyone!  This semester is steadily rolling along and I think everything is going quite well.  This week we will be talking about heating and cooling and specific heat capacity.

For Students:
We can't talk about specific heat capacity without first talking about the unit of energy, (remember heat is a form of energy), the joule.  The joule is name for James Joule:

Joule was the son of a wealthy brewer in Manchester, England.  The family wealth and the workshop in the brewery gave Joule the opportunity to pursue scientific studies.  Among the topics that he studied was the issue of whether heat was a massless fluid.  He eventually figured out exactly the nature of heat!
The calories in the food you eat are actually measured in Kilocalories, which is 1000 calories.  A calorie (not a kilocalorie) is equal to 4.184 joules.
When an object is heated or cooled, the quantity of energy transferred depends on three things:
1.  the quantity of the material
2.  the amount of temperature change
3.  the material itself
Specific heat capacity (c) is the energy transferred as heat that is required to raise the temperature of 1 gram of a substance by 1 kelvin.  The units are joules/g*k (joules per gram kelvin).   For solving these types of problems, first you need to find the change in temperature.  This is the final temperature - the initial temperature.  It is given in Kelvins.  Then you need the formula:
                                    q (heat) = C (specific heat) x m (mass) x change in temperature

We will be working on these this week!

For Parents:
I mentioned the field trip and it is coming!  We will be going to the Great Lakes Science Center in 3 weeks.  You should be seeing a permission slip home this Friday.  Your student must pack a bag lunch and can bring money for the gift shop if you'd like.  We will be leaving school at exactly 9 am and returning at 2 pm.
Great Lakes Science Center

Thanks again, and have a nice day!

Energy and Chemical Reactions

What makes this hot air balloon rise?  Actually, a propane burner heats the air inside the balllon until the air is heated enough to be less dense than the air outside, causing it to rise.  Energy in the form of heat is needed to make this work.  Similarly, energy (usually in the form of heat) is needed in many chemical reactions.

For Students:
The science of heat and work is called thermodynamics.  This week we will be learning about the relationships between energy changes, heat and work.  We will also be talking about how we can determine whether a chemical reaction is product favored or reactant favored.  Energy can be defined as kinetic or potential.  Kinetic energy is the energy of motion, it can describe the motion of atoms, molecules, a moving tennis ball, or automobile.  Basically anything moving in anyway has kinetic energy.  Potential energy is stored energy and is directly related to an object's position.  Holding a ball at the top of a waterfall has potential energy and so does energy stored in fuels.  Finally, the Law of Conservation of energy states that energy can neither be created or destroyed.  Energy is always constant, it can remain the same or change forms, but the amount of energy in the universe is always constant.
The answers to last week's quiz are:
1.  OH-    -->  hydroxide
2.  Cyanide  -->  CN-
3.  Carbonate  -->  CO3 (-2)
4.  nitrite  --> NO2 (-)
5.  PO4 (-3) --> phosphate
6.  NO3 (-) --> nitrate
7.  SO3 (-2) --> sulfite
8.  CLO (-) --> hypochlorite
9.  sulfate --> SO4 (-2)
10.  chlorite --> CLO2 (-)
11.  chlorate --> CLO3 (-)
12.  perchlorate --> CLO4 (-)
13.  CrO4 (-2) --> chromate
14.  CH3CO2 (-) --> acetate
14.  MnO4 (-) --> permanganate
15.  HCO3 (-) --> bicarbonate

Hope everyone did well!

For Parents:
The quiz grades seem to be slipping a bit, so just a reminder: if your child needs help please instruct them to see me after school or during lunch break.  I am always willing to help!  Also, FYI  we will be going on a field trip to the Great Lakes Science Center in Cleveland.  This trip is still a few weeks away and permission slips will be going home soon.  Thanks again for all you do!

Naming Ionic Compounds

For Students:
So far we have talked about molecular compounds.  Ionic compounds are another major class of compounds.  They are made up of ions, which are atoms or groups of atoms that bear a positive or negative charge.  Many familiar compounds are composed of ions.  Table salt (NaCL) and lime (CaO) are just two examples.  In order to recognize ionic compounds and to easily write formulas for these compounds, it is important to know the formulas and charges of common ions.  You also need to know the names of ions and be able to name the compounds they form.  Unfortunately, this is something that must be memorized.  Ions are composed of two different types.
Cations are atoms that lose an electron (or two, etc.)  Losing an electron give a positive charge so all cations have a positive charge.   Some examples are Li+ and Ca +2.  Elements on the left side of the periodic table typically are cations.  The left two columns are the most common.
Anions generally have a negative charge due to the gaining of one or more electrons.  An example is O -2.

These ions can be monatomic (single atoms) or polyatomic (two or more atoms).  The following are common polyatomic ions that should be memorized:

For Parents:

The density experiment is this week and before we begin to learn what different materials' densities are, we will be watching this fun video:



Have a great week and don't forget, Density = mass/volume!