Percent Composition

Percent composition is just like determining your grade - the amount you got divided by the the whole amount. 

With compounds, you find the mass of a particular element and divide it by the mass of the whole compound. So if you wanted to know the percent composition of oxygen in water, you would take the mass of oxygen and divide it by the mass of water. 

We practiced some basics and the students measured the amount of sugar found in DubbleBubble bubble gum. 

Students each had a piece of gum and observed the gum by weighing it, drawing it, and smelling it. The students chewed the gum for ten minutes. While they were waiting we watched How Its Made on bubblegum.

After ten minutes, students did more observations and re-weighed the gum. The gum weighed less... why? Because the sugar dissolved and was lost. Using this weight difference, students determined the percent composition of sugar in the gum they chewed. They also can convert the grams to moles and determine how many moles of sugar were in the gum.

Expanding Horizons: Insect Venom

The original Compound Interest article on insect venom and the Schmidt pain index can be found here. Please look at the graphics and read the article.

You can listen to an interview with Schmidt who developed the pain scale here (it is the first ten minutes) on a RadioLab podcast (I highly recommend their shows).





Still curious?
What's the difference between poison and venom? There's a TedEd Talk on that! Watch it HERE.

How does your brain respond to pain? There's a TedEd Talk on that! Watch it HERE!

Want to know more about ant colonies? There's a TED talk on it. Watch it here.

Moles? What the heck!

Moles are used to count atoms. There are 22,000,000,000,000,000,000 quintillion atoms in a grain of sand and even counting grains of sand is a pain. Because atoms are so tiny, we use the mole to estimate.

There are 6.02 x 10 ^23 molecules in one mole. That's a whole lot. This is our new favorite number because it needs to be memorized. We will practice converting from moles to molecules.

Next we discussed molar mass. Molar mass = 1 mole and it also equals atomic mass from the periodic table. To find the molar mass of carbon dioxide you find the mass of carbon and two oxygens and add them together. Finding molar mass is not difficult unless the molecule has tricky subscripts (which we have been practicing).

The third thing about moles is that "one mole of any gas will occupy 22.4 Liters." 22.4 is another favorite number. We can convert from moles to liters and from liters to moles. 

Just how big is a mole? There's a TedEd talk on that! Watch it here!

Conversions

Conversions, or dimensional analysis, are used to change one unit to another. This is really useful when converting to metric units, but is essential to chemistry in terms of mole conversions. Setting up conversions is a skill so we started with learning the format. There are plenty of how to videos out there on the internet for anyone needing a tutorial.

We practiced conversions with some of the crazy things people do to get in the Guinness Book of World Records - like longest ear hair, skinniest waist, tallest man, etc. I think the one the kids thought was the weirdest was the lady who can pop her eyes out 12mm.

Check out more crazy records here!

SigDigs and Sci Notation

Significant digits are used so that our calculations are not more precise than our measurements. All digits other than zero are significant.

Its the zeros that are the tricky ones. We went over the rules and then did some practice situations. We will continue to practice this and all calculations made for the rest of the year must be rounded to the correct number of significant digits. 

Scientific Notation is used for very large and very small numbers that usually have a lot of zeros to make the numbers for manageable. Most students are familiar with scientific notation and just need a bit of practice. 

Expanding Horizons: How Big is a Mole?

Video Citation

Last Name, First initial. Middle initial. [Username if no real name is given (still last name, first name)]. (Year, Month Date). Title of video(underline). [Video File]. Retrieved from URL. 

    Typed Video Example:

AsapSCIENCE. (2015, March 15). What Happens If All The Bees Die? [Video File]. Retrieved from https://www.youtube.com/watch?v=JilYBVrFiLA

Video 1: How big is a mole? And what is a mole? A TED-Ed

Video 2: Why Mendeleev is a genius! A TED-Ed

Video 3: Why do your feet smell... and what can you do about it?

Just for Funsies

“From Outer Space to Under Our Skin: A Look At The Universe”

http://ed.ted.com/featured/qwxLv7Xd#watch                    

This video is old, but interesting to think about. Note 10⁰ = 1.

Chromatography

Chromatography is the separation of liquids based on particle or molecule size. 

Chromatography is used to separate inks into the colors that make them up. Most inks are mixtures of colors and the ink will separate into bands of colors based on the size of the different ink molecules.The small particles move faster and will move further up the paper strip (in the photo black); the larger particles do not move as far (yellow). Some black inks are actually made up of blue red, pink, and yellow.

Pairs or groups of students received a strip of filter paper and made a pencil line about 3 cm from the end. They then traced over the pencil line with a marker, dipped the edge of the paper into water and waited. Over time the water will travel through the paper carrying the ink molecules with it. Smaller molecules are easier to carry and travel further.

Chromatography can be used to separate any mixtures with different size particles and actually gel electrophoresis used for DNA analysis works on a similar principle.

LD50

This week's topic is about lethal doses and LD50.

The second portion is about the difference in toxicity of natural vs. manmade chemicals. Most people wrongly assume that if a chemical is natural that is good and that if a chemical is manmade then it is bad. Both can be good and both can be bad!

Compound Interest's original post about Lethal Doses of Common Chemicals can be found here. 
Compound Interest's original post about Natural vs. ManMade Chemicals can be found here. 

Lab Equipment

Students need to be familiar with certain lab equipment and its purpose, even if we won't use all of it in labs for high school chemistry. Students identified equipment using examples of the real thing (we made this into a contest) and also by identifying black and white drawings.

Students will sort equipment based on what its main purpose is. Some equipment is used for liquids, some for solids, and some for heating. Some is used for all of those things. 

The three pieces of equipment most likely to come up, and the most confusing when in black and white photos are the watch glass, evaporating dish, and the crucible (which has a lid). All three of these can be used for heating substances to remove water among other things. In real life they look different - but in drawings they look similar. How to tell them apart? The watch glass resembles a contact lens; the evaporating dish has a pour spout; and the crucible is more cup shaped and often is pictured with a lid. 

Here is an online quiz on lab equipment with photos! Try it!

Hazard Diamond

Most of us have seen these diamonds on trucks as we pass them on the highway. These diamonds are useful for safety and response teams to identify what is in the truck so the correct precautionary and clean up measures can be made. 

The NFPA 704 fire diamond (or hazmat diamond) is described in NFPA Standard 704, maintained by the National Fire Protection Association. The system identifies four key hazards (health (blue), flammability (red), instability (yellow), and special (white)) and their degree of severity. Hazard severity is rated numerically, ranging from 0 (minimal) to 4 (severe).

The hazard diamond is useful because it allows emergency personnel to quickly and easily identify the risks posed by hazardous materials and is  useful to determine what, if any, special equipment should be used, procedures followed, or precautions taken during an emergency response. (Summarized & more information here.)

Want to make your own customizable hazard diamond? Click here. Why does this feature exist? So people can make easily identifiable hazard diamonds for any chemical they have on hand. 

Welcome!

Greetings students, parents, and guardians.

Welcome to a new school year with Ms Jancaitis! This blog has been set up to connect students, parents, and guardians with the chemistry class.

Each student will receive a course syllabus. The course syllabus outlines what the course will be like, what topics will be covered, and course expectations. It also contains contact information. There will be a quiz on this syllabus on Monday.

Our first unit will cover lab safety and equipment. Each note packet comes with the safety rules and contract. The safety rules and contract need to be read and signed by both the student and parent guardian. The safety rules are rules designed to keep the classroom safe and orderly to maximize learning and prevent accidents and injuries. These rules need to be studied because there will be a safety test and infractions of these rules can lead to disciplinary action as well as low assignment grades. A contract holds students accountable for the items that are broken if the student is acting a manner that is unsafe for themselves or those around them.

Please have these papers signed and returned by Monday. Students not returning signed safety rules and safety contracts will not be able to participate in labs and activities until the contracts are signed and returned.