Jan 15-18

This week, I learned more about the difference between mixtures, compounds, and elements.

Essentially, this reminded me of when I had to learn this in 6th grade. I had a vague idea of what each were and their differences. So, I went with my hunch and guessed that mixtures were like putting Snickers in a shake. Even though you physically combine both, you don't change any of their properties. The Snickers are still Snickers, and the shake is still a shake. Now, compounds are a different story. If I remember correctly from 6th grade, compounds were when two or more elements were chemically combined and their properties changed chemically. Elements were their own separate entities that contained their own properties.

Over this week, we went over problems involving this topic. We looked at pictures on the Google Drive. One of the pictures looked like two blacks combined together. At a first glance, it seemed to me like an element, but as I looked closer, I realized that it may be different from the elements that were combined to make this arrangement. So, this question came up in class: Is it an element, or is it a compound? This then reminded me of O for Oxygen and O2, and H for Hydrogen and H2. One rationale was that since two of the same elements combined, then they would be still an element. Another argument was that they combined to form a different compound. So, what is it? One or the other? Or, is it something? However, we did come to a consensus that this was a diatomic substance. But, I then realized that this was a molecule. Therefore, I came to the conclusion that diatomic elements are molecules, that elements of the same kind can combine to make molecules, and that neither seemed to change chemical properties. I think, therefore, that since they both had the same properties, they combined without changing their properties.

Next, I looked at two pictures. One showed one element combined to a different element and then another one with a different element but not combined. The top picture shows two elements in a substance not chemically bonded. Therefore, this is a mixture because the elements have still retained their properties, and as a result, they haven't changed. On the other hand, the bottom picture showed two different elements chemically combined together. Therefore, this is a compound because their properties have changed as they have formed a new substance.

In class, here was another challenge. Let's just say that there were 2 pairs of H2O and each pair represent 100 mL, so there are 200 mL of H2O overall. The question was this: What percentage of volume does each take up? This means don't look up the atomic mass of hydrogen and oxygen. So, what I did was this. I considered the H2O molecule overall. The water molecule consists of 2 Hydrogens and 1 Oxygen. Therefore, I considered a 2 to 1 ratio. So, overall, H2 is 2/3 of water molecule and the oxygen was 1/3. But, we are only considering half of the overall volume. This is fine, though, at least this demonstrates an overall understanding of how much space each element takes up in a molecule. Even though there were 2 H2O molecules, the percentage of Hydrogen is still 2/3 (67%) and the percentage of Oxygen is still 1/3 (33%). Also, one way of considering this is drawing H2O and H2O in a box, then separating the H's and the O's. What you get is two H2 pairs and 1 O2 pair. If you did this correctly, you should get a 2 to 1 ratio. You should get 4 H's and 2 O's. The total is 6 elements. Therefore, the fraction of H's is 2/3 of the volume, and the fraction of the O's is 1/3.

So, what are their volumes overall? Since Hydrogen consisted of 2/3 of 200 mL, there are 134 mL of Hydrogen, and since Oxygen consisted of 1/3 of 200 mL, there are 66 mL of Oxygen. Therefore, no matter how many molecules you consider, the ratio must remain the same in order to correctly calculate its overall percentage.

Next, there was this problem: hypothetically, there are H2 in a container of 50 mL and O2 in a container of 50 mL. What would be the volume of the two if they were to combine? Suddenly, I had this hunch that this was H2O2 (hydrogen peroxide). I remembered that this was mentioned in 6th grade, so I considered that if they combined, then they would form a new substance. But, how would that affect the volume? Well, I thought that since they chemically formed a new compound, the volume would be 50 mL based on the overall average of the volumes. So, this makes me think of the possibility of the volumes of two different elements together combining and then averaging out to equate to a new volume in case the volumes were either the same or different.