<p>If you are interested in significant figures in more detail, here are some <a href="https://www.khanacademy.org/math/pre-algebra/decimals-pre-alg/sig-figs-pre-alg/v/significant-figures" target="_blank">good videos</a> to follow on Khan Academy.</p><p>This week we will continue our explorations of matter and energy. We will discuss the sub-atomic particles that govern chemical reactions, isotopes, anions, and cations. We will learn how to name compounds, calculate formula masses, convert between grams and moles, examine periodic trends, and more! An advanced problems set is posted now; that is a longer assignment and is optional unless you would like to be eligible for the Honor’s Track. You can still earn a regular verified certificate without completing the advanced problem sets, so please be sure to keep working on the normal weekly exercises.</p>

<p>In this week's videos and exercises (aka quizzes), we will learn how to name compounds, calculate formula masses, convert between grams and moles, examine periodic trends, and more!</p><p>I hope you enjoyed the last two weeks of learning chemistry. Great work on watching videos, posting on the discussion forum and submitting your exercises!</p>

<p>Week 4 for Introduction to Chemistry: Reactions and Ratios is about to begin! This week will be filled with introductions to chemical compositions, chemical reaction terminology, and reaction calculations.</p><p>If any of the following questions interest you, then watching this week's videos and doing some practice problems are probably a good way to get started! How much sodium is in my diet? What amount of pollutants are in drinking water? How much iron is in iron ore for steel production? These of the types of problems you will be able to address this week.</p>

<p>In the past five weeks of the course, we have learned concepts, rules, and skills, including but not limited to: the definitions of atoms, elements, molecules, and compounds; energy changes; Coulomb’s Law, molecular stoichiometry; atomic structures; periodic trends; the mole; compounds; atomic and molecular masses; molecular stoichiometry; balancing chemical equations.</p><p>In this coming week, we will be discussing aqueous solutions, solubility rules, precipitations and electrolytes! We are also going to learn the first type of chemical reaction equation in this course: Dissolutions.</p>

<p>We are almost at the end of our course! I hope this has been a rewarding experience for you because I know that the course is not an easy one and it is relatively long. So kudos to everyone who has made it this far!</p><p>Week 6 for Introduction to Chemistry: Reactions and Ratios will include very basic introductions to acid-base and redox reactions. We will also practice combining what we know from previous weeks to complete reaction calculations.</p>

Congratulations on making through to the final week of the course! It was not an easy journey for the past six weeks with dozens of videos, exercises, problem sets, and forum discussions. Kudos to the many of you who completed the honors lessons on top of the other work. I am proud of all of you!