Untitled

If you have taken a pre-AP chemistry course in school, this chapter should serve as a review. We assume that you know about the scientific method, elements, compounds, and mixtures. We will not spend a lot of time discussing elementary chemistry topics. Take your textbook with you when you use this book. Review your textbook if we mention a topic that doesn't sound familiar. Topics that are on the AP exam will be covered by us. There is a lot of good information in your text that is not covered on the AP exam, so if you want more, read your text.

The format that is used on the test has been tried as much as possible.

The majority of chemistry calculations involve a number and a unit. If your units have been canceled and the desired unit written with the number, be sure to complete the calculation.

The metric system is related to the system of units used in chemistry. There are units for length and mass. Since most of us don't think in these units, it's important to be able to convert back and forth from the English system to the SI system.

Knowing the others will allow you to simplify your calculations, although they are useful.

Most of the world measures temperature in Celsius, but we in the United States think of temperature in Fahrenheit.

The scale is used by chemists in working with gases.

In chemistry, the density of a substance is calculated. Density is independent of the quantity of matter and can be used for identification. g/ cm3 is the most common unit for density in chemistry.

There are two types of numbers in chemistry. By definition, exact values are just that. There is no uncertainty about them. There are 12 items in a gross. Because of the limitations of our measuring instruments, measured values have uncertainty associated with them. The answer must reflect the combined uncertainty by the number of significant figures that are reported in the final answer. The certainty in the answer is greater when significant figures are reported.

Carry as many as possible until the end and then round off the final answer as the measurement may contain different numbers of significant figures. Significant figures reported in the final answer will be determined by the least precise measurement.

Zeroes between zero and zero are significant.

The first non-zero digit has zeroes to the left of it.

Zeroes to the right of the last non-zero digit are not significant if there is no decimal point.

Rule 4 is a convention that many of us use, but some teachers or books may use alternative methods.

6 significant figures would be contained in 230,500, but only 4 would be.

The number of significant figures in a number can be expressed in scientific (exponential) notation. The number of significant figures is shown. 2.305 x 10-5 contains 4 significant figures. You might need to review it.

Round off the answer to the same number of significant figures in the measurement with the least significant figures.

The factor label method is a method for setting up mathematical problems. The units associated with the numbers are canceled when only the unit of the desired answer is left. The final answer can be calculated and rounded off to the correct number of significant figures after the mathematical operations are done.