Thursday, October 28

Thursday was test day. We took the Unit 3 test with 15 multiple choice questions, a page of short calculations and a page of longer calculations.  This day marks the official end of Unit 3.

Unit 4 will begin on Friday. Unit 4 is concerned with the topic of chemical reactions. We will learn what a chemical reaction involves and how different reactions can be characterized based upon their features. We will also learn how to use atom counting as a means of balancing chemical equations via the trial and error method. The unit will end as we focus upon precipitation reactions and learn to predict what precipitate will form as two aqueous solutions of ionic compounds are mixed. There will be virtually no mathematics in this unit. There will be a lot of symbolic representations.

Monday, October 25th

In chemistry today, we started out by receiving our grades. Mr Henderson also reminded us of our Test on Thursday along with our delicious bookmark which is due at the end of the unit. Then we moved on to our lesson of the day which was mass composition and empirical and molecular formulas. Our lesson for today was on the packet page 13. We started out by finding the molecular or empirical formula’s of certain compounds with a given molar mass. As an example in the compound Octane, the molar mass was 114.2 g/mol, and the molecular formula was given to be C8H18. Mr. Henderson then explained that the empirical formula was C4H9 because it was the simplest ratio of the molecular formula.

In a second example, we were given the compound Benzene and the molar mass was 78.1 g/mol. The empirical formula CH was given and there are many possibilities for a molecular compound from this formula, so the Mr Henderson explained how you can find the molecular formula through the molar mass. For this problem we found that the mass of Benzene was six times that of the empirical formula, so therefor the molecular formula would be C6H6.

We then did a word problem together where we had to determine the empirical and molecular formula of an unknown carbohydrate when given the percent ratios of the elements and the molar mass. We solved this by assuming that that there was 100.00g of this substance, then we multiplied each of the percentages by their molar masses and from this we got the empirical formula which we compared with the molar mass to get the molecular formula.

Finally we finished the class with the Formula of a Hydrate Lab. In this lab we had to determine the chemical formula of the hydrate of copper sulfate by weighing the copper sulfate before and after we burned all the moisture out of it.

Friday, October 15 - Unit 3

Friday was test day. We took the Unit 2 test with 33 multiple choice questions and one page of naming and formula writing with a short calculation. There were 50 questions worth 2 points each. Up-to-date grade printouts will be available on Monday.  This day marks the official end of Unit 2. 

Unit 3 will continue on Monday. (We've already had a day and a half of this unit, in which we learned how to use conversion factors and the meaning of the atomic mass unit and relative atomic masses.) As we continue through Unit 3 we will learn about the mathematical relationships associated with the chemical formulas. We will learn that a chemical formula reveals quantitative information about the gram-to-gram and atom-to-atom relationships for the elements within a chemical compound. This unit will be the first of several math intensive units within the course.

Monday, October 18, 2010

Who is Amadeo Avogadro? Why, only the most famous scientist ever! Why is he so famous? He thought of the mole, that's why. The mole is a scientific unit. It is used in measurement, mostly in chemistry. The mole is abbreviated as "mol". But why is this significant? Today, we started Unit 3. Unit 3 focuses on stoichiometry, or the science that deals with the quantitative relationships that exist between products and reactants. (conversion factors) The number mole, is mathematically written as 6.022 x 10 to the 23rd

To begin our class today, Mr. Henderson passed back our grade reports, with the Unit 2 Test inscribed upon its face. Mr. Henderson also told us about the National Mole Week recently declared by President Obama. With that, we began class.

We took some notes and filled out a leaf of paper in our Unit 3 Packet. It focused on finding the number of moles of a certain atom in some situations and and finding the number of atoms in others. These are two very different ideas. Using conversion factors we learned earlier, we were able to make short work of these four problems we were given. Mr. Henderson also showed us how to find the number of atoms in a certain mass of an element. For example, let's take 12.01 grams of carbon. The number of atoms for this amount of carbon would be 6.022e23. (1 mole) How did we get that? The average atomic mass of carbon is 12.01. If you have an atom, with its average atomic mass in grams, just put down one mole as your answer. However, if the mass in grams is slightly smaller or larger than your given atom's AAM, you take the 6.022 from the mole and divide or multiply accordingly. For example, let's say you had 20 grams of calcium. The AAM for calcium is about 40. Because this is half, you would take 6.022 and divide by two. Your answer shall be 3.011 x 10 to the 23rd. (you keep the last part of the number)

To end the class, we started our MR1 lab. (after getting new lab groups and moving to new seats) This is the H2O challenge lab. We have to count how many molecules there are in a sample of water. Since we cannot see molecules, we must count them in a different way. By using the mol, of course. We add the AAM of two hydrogen atoms to the AAM of one oxygen atom. However, not everyone finished this lab in class today and Mr. Henderson will let us finish it tomorrow. For anything else check his website.

Friday, October 15

Friday was test day. We took the Unit 2 test with 33 multiple choice questions and one page of naming and formula writing with a short calculation. There were 50 questions worth 2 points each. Up-to-date grade printouts will be available on Monday.  This day marks the official end of Unit 2. 

Unit 3 will continue on Monday. (We've already had a day and a half of this unit, in which we learned how to use conversion factors and the meaning of the atomic mass unit and relative atomic masses.) As we continue through Unit 3 we will learn about the mathematical relationships associated with the chemical formulas. We will learn that a chemical formula reveals quantitative information about the gram-to-gram and atom-to-atom relationships for the elements within a chemical compound. This unit will be the first of several math intensive units within the course.