In a few more posts (I would like to say 2 or so, at this point) I will be done with reviewing the first chapter of study in your standard inorganic or general chemistry textbook. I have used many chemistry textbooks in order to provide the reviews that I have provided, and thus each chapter was not the same, but in a few more posts will be about where most textbooks that I have looked at conclude their introductory chapter. As I mentioned, I will be uploading a review sheet that goes over all of the topics that I have reviewed so far, in a very concise way. This makes it easy for you to get the general gist of what went on. Using the review sheet, you can also see what topics you need to go over due to weaknesses in those topics, and review those topics individually.
For one of my final “first chapter” posts, I will go over the concept of derived units. It is something that you have probably practiced before in math classes. A derived unit is a unit created from any combination of the seven SI base units. A very simple and common example is the concept of area. Area is derived from the multiplication of two units of length (and in chemistry, these units will be SI units, and if they area not, you must convert them!). Given that the SI unit of length is a meter, the SI unit for area would be meters squared (Ebbing and Gammon 2009).
SI units can be derived using other operations as well. You will become familiar with speed (and velocity, acceleration, and more…) in your university physics class. The SI unit for speed is derived from two other SI units. Speed is defined as distance/time. The SI unit for distance is meters and the SI unit for time is seconds: therefore, the SI unit for speed is meters/second (Ebbing and Gammon 2009).
Units can be derived in many different ways. Volume is given by a measurement of length cubed. In SI units, this is meters cubed. The density of an object is a very common derived unit, and it is a very important concept in chemistry because density helps us identify an object. Density is a characteristic of a substance. Density is defined as the mass per unit volume of an object, and is written as d = m/V, where d is the density, m is the mass, and V is the volume. Given that the SI units for for mass and volume are kilograms and meters, respectively, the SI unit for density is kilograms/meters cubed (Ebbing and Gammon 2009).
Sometimes, you will be faced with problems that are not written in SI units, and may be written in units of grams for mass and centimeters cubed for volume, respectively. I will go over briefly how to do proper unit conversions in these cases, in a separate post. However, soon I will also have the first MCAT review question up for you, so look out for that as well.
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