Beginning of Year Material Chemistry 1-2 and Honors Chemistry 1-2

What is chemistry? Chemistry is the study of matter and its changes. Chemistry has five major divisions and they are: organic chemistry is the study of essentially all substances that contain carbon, inorganic chemistry concerns substances that do not have carbon, analytical chemistry is concerned primarily with the composition of substances, physical chemistry is concerned with the theories and experiments that describe the behavior of chemicals, and biochemistry is the study of the chemistry of living organisms.

What is the scientific method? The scientific method is an approach to the solution of scientific problems. This method begins with an observation of a phenomenon. Then, scientists must propose an explanation or hypothesis, which is a proposed reason for what is observed. Scientists must test their hypothesis through experiments. Scientists can prove a hypothesis true if it explains what they observe during multiple experiments. If experiments prove the hypothesis wrong then scientists must revise their hypothesis and test it again.

If the hypothesis can explain experimental observations then it rises to the level of a theory. A theory is a thoroughly tested explanation of why experiments give certain results. Theories can change over time if new evidence comes along. Before publishing anything, scientists must allow their work to be peer reviewed where other scientists scrutinize their work and try to reproduce their results (hence why they must provide a procedure in their article) Scientific Laws explain natural phenomenon but do not try to explain them.

Famous Scientists who used the scientific method.

What are physical and chemical properties? Physical properties are the qualities or conditions of a substance that can be observed or measured without changing the substance’s composition (such as change of state, density). A physical change alters a substance without changing its composition. Chemical properties are the ability of a substance to undergo chemical reactions and to form new substances. Chemical changes alter the composition of a substance.

Physical Change

Chemical Change

What are significant figures? Signficant figures in a measurement include all the digits that are known precisely plus one last digit that is estimated. Any non-zero digit is significant. Zeros that are after or between any non-zero digit are significant. Zeros that come before a non-zero digit are not significant.

How many sig figs do the following measurements have? x

How do we use sig figs in calculations? Addition and Subtraction: The answer to an addition or subtraction calculation should be rounded to have the same number of decimal places as the measurement with the least number of decimal places. Multiplication and Division: The answer is rounded off to the number of significant figures in the number with the least significant figures.

Complete these problems Answer the following and round to the correct number of significant figures: 7.21 x 6.3= =

What is scientific notation? In scientific notation a number is written as the product of two numbers: a coefficient and a power of 10. If numbers are > 1 then you move the decimal place to the left until there is only one number in front of the decimal. The number of times that you move to the left equals the positive exponent. If numbes are <1 then you move the decimal place to the right until there is only one number front of the decimal. The number of times that you move to the right equals the negative exponent.

You do the opposite to get numbers out of scientific notation. What will the following numbers be in scientific notation? Convert out of scientific notation: 2.5 x 10 3, 3 x 10 -6

Do the following calculations: (3 x 10 8 ) x (5 x ) (3 x 10 8 ) / (5 x )

What are the metric units? Length= meters (m) Temperature= Celsius (C) Volume (the amount of space that an object occupies)= Liters (L) Mass (the amount of matter in an object)= Grams (g) Weight= Newtons Time=seconds Amounts in metric units are based on prefixes. Look on pg. 39 (pg. 8 for honors chem) for those prefixes. They are there for length but you can apply them for any metric units. In honors chem book, pg. 14 has metric and English unit conversions)

What are conversion factors? Conversion factors are ratios of equivalent measurements. In order to write conversion factors, we must use an equivalency (such as 1000 m = 1 Km). We place one of those units on top and the other on the bottom. We flip that order to get the second conversion factor. Each equivalence gives two conversion factors. Write conversion factors for the following equivalence: 1 m = 1000 mm

How do we convert between units? We use conversion factors in order to convert between units. The number that we are given goes outside of the conversion factor. The units that we want (from the equivalence) go on top of the conversion factor while the units that we want to cancel (from equivalence) to on the bottom of the conversion factor. You multiply the given number by what is on top and divide by what is on the bottom.

Problems Convert 20 lbs. To kilograms (2.2 lbs=1Kg). Convert 2 L to mL (1L=1000 mL).

How do we do two-unit conversions? Two unit conversions involve two units (like a distance over time problem). We must convert each unit, one at a time, in order to complete two unit conversions. The first conversion will convert one unit while the second conversion will convert the other unit.

Convert 20 m/s into mi/hr. 1 hr=3600 s and 1610 m =1 mi Lake Powell spillways let out water at a rate of 5000 L/s. Convert this to gal/min. 1 gal=3.68 L and 60 s= 1 min

What is density? Density is a physical property of a substance that describes the amount of matter in a given volume of a substance. Substances that are less dense than water will float while substances that are more dense than water will sink. You can apply this logic to any substance. Density= mass (g)/ volume (mL)

Ice is less dense than water

Problems Substance X has a volume of 3 mL in 6 grams of mass. What is its density? Water has a density of 1 g/mL. Would substance X float in water? Gold has a density of 19.3 g/mL. What is the volume of 12 g of gold?

What are elements? What are compounds? Elements are the simplest forms of matter than can exist under normal laboratory conditions. Element symbols are either one to two letters long. The first letter is always capitalized. The second letter is always lower-case Compounds are substances that can be separated into simpler substances only by chemical reactions. Compounds are made of multiple atoms of the same element or two or more elements.

Element Compound

What can compounds tell us? Compounds can tell us the numbers of each element, in the compound, based on the formula. Subscript numbers written to the right of an element apply to that element only. If there is just one of that element then we write nothing next to it. Subscript numbers that are outside of parentheses affect the elements within the parentheses (the numbers of each are multiplicative). Coefficients, the numbers that are in front of the compound, affect all the elements within the compound.

Problems Classify each as an element of compound. Name the elements present and if it is a compound then tell how many of each element is present. CuCO 2 NaNO 3 Mg(NO 3 ) 2 2Ca 3 (PO 4 ) 2