C150-20230825-Conversion Factors and Atomic Theory

 A couple of valuable tools today as we ramp up:

Conversion factors are not magic, they're just fancy versions of "1". For example:

1 gallon = 3785.41mL

Dividing both sides by "1 gallon" gives:

1 = 3785.41mL / 1 gallon

Dividing both sides by "3785.41mL" gives:

1 = 1 gallon / 3785.41mL

Both are just fancy versions of "1". When you change units by multiplying by a conversion factor, use the units to decide which one to use. If you have gallons and want mL, then multiplying by "mL / gallon" will cancel the gallons unit and leave you with mL.

We also looked at some of the foundations of atomic theory, including looking at protons, neutron, and electrons as well as the numbers that we use to keep track of them: Atomic Number, Mass Number, and Charge.

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C150-20230823-Classifying Matter and Changes, Measurements in Chemistry

 We often engage in "sorting" activities where we define a couple of distinct categories and then try to sort a bunch of properties or observations into those categories. Today we did some sorting…

Matter sorting categories:

• Solid/Liquid/Gas - These are the standard states of matter.
• Intensive/Extensive properties - Intensive properties are defined by the identity of the matter, such as density or elemental composition. Extensive properties describe the amount or form of the matter, such as mass or shape.
• Elements/Compounds/Solution/Heterogeneous mixtures - Pure substances can either be elements (if they're just made of 1 type of atom) or compounds (if they are made of multiple types of atoms in faxed ratios). For mixtures, a homogeneous mixture has the same composition throughout (usually called a solution) and a heterogeneous mixture will have varying composition depending upon where it's being sampled (like a chocolate chip cookie).

When we're looking at how matter changes, there are also two important categories for sorting: chemical change or physical change. Chemical change alters the atomic or molecular nature of the system undergoing change, physical change alters its form or state. Melting ice, dissolving sugar in water, and crushing an aluminum can are all physical changes. Burning sugar, tarnishing metal, and baking a cake are all chemical changes.

In order to observe these changes, we often need to measure something. Taking measurements always involves some degree of uncertainty or variability. This is often called "error", but it doesn't necessarily mean that a mistake was made, it just means that every measurement process has some uncertainty. One way that we can include that uncertainty in values we report is by the use of significant figures. There's a more detailed description of sig figs here: https://chembits.com/GenChem/SigFigs2021a.pdf

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Daily Updates

 As we begin a new semester and I think about ways to most effectively communicate with my students, I think I'm going to try and return to something that I used to do a long time ago. Once upon a time, every day after my Gen Chem class, I would use "the bird app" to post a recap or highlights of class that day. It was a fun challenge for me because (at the time) each post was limited to 140 characters, and I liked trying to distill a days worth of topics into just a few 140-character posts.

Now that the bird app has changed so much, I don't really want to use it for anything substantial, but why not use one of my existing platforms to try and do the same thing? Without the 140-character limit, I'm a little anxious that I'll launch into long, rambling posts that will not be as effective as those short blurbs, but that will be a good challenge for me.

So starting with tomorrow's class, I will be posting recaps of my General Chemistry lectures each day that we have class. To try and organize them and make them a little more search-friendly, I'll tag them with #DrBodwinChem150. That's the plan.