Summer 2017 Elements Honors Chemistry

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Please fill out the chart using the periodic table on the bottom of this paper. You will need to have all the information on the table memorized by the first day of school. Spelling counts

Element Name Symbol Atomic Number (not the decimal number)

Element Name Symbol Atomic Number (not the decimal

number) Aluminum Lead

Argon Lithium Barium Magnesium

Beryllium Mercury Boron Neon

Bromine Nickel Calcium Nitrogen Carbon Oxygen

Chlorine Phosphorous Copper Potassium Fluorine Silicon

Gold Silver Helium Sodium

Hydrogen Sulfur Iodine Tin Iron Uranium

Krypton Zinc

Units of Measure

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How were sailors able to measure the depths of seas? Back in the days before all the electronic gadgets for measuring depth and locating undersea objects existed, the "fathom" was the unit of measurement for depth. A rope was knotted every six feet and the end was dropped over the side of the ship. You could tell how deep the water was by how many knots went under the water before the rope hit bottom. Today, we just turn on an instrument and read the depth to a high level of accuracy. Length and Volume

Length is the measurement of the extent of something along its greatest dimension. The SI basic unit of length, or linear measure, is the meter (m). All measurements of length may be made in meters, though the prefixes listed in various tables will often be more convenient. The width of a room may be expressed as about 5 meters (m), whereas a large distance, such as the distance between New York City and Chicago, is better expressed as 1150 kilometers (km). Very small distances can be expressed in units such as the millimeter or the micrometer. The width of a typical human hair is about 20 micrometers (μm). Volume is the amount of space occupied by a sample of matter. The volume of a regular object can be calculated by multiplying its length by its width by its height. Since each of those is a linear measurement, we say that units of volume are derived from units of length. The SI unit of volume is the cubic meter (m3), which is the volume occupied by a cube that measures 1 m on each side. This very large volume is not very convenient for typical use in a chemistry laboratory. A liter (L) is the volume of a cube that measures 10 cm (1 dm) on each side. A liter is thus equal to both 1000 cm3 (10 cm × 10 cm × 10 cm) and to 1 dm3. A smaller unit of volume that is commonly used is the milliliter (mL – note the capital L which is a standard practice). A milliliter is the volume of a cube that measures 1 cm on each side. Therefore, a milliliter is equal to a cubic centimeter (cm3). There are 1000 mL in 1 L, which is the same as saying that there are 1000 cm3 in 1 dm3. To determine the volume of a liquid, usually in a graduated cylinder, you look at the bottom curve which is called the meniscus, the curve seen at the top of a liquid in response to its container. When you read a scale on the side of a container with a meniscus, such as a graduated cylinder or volumetric flask, it's important that the measurement accounts for the meniscus. Measure so that the line you are reading is even with the center of the meniscus. For water and most liquids, this is the bottom of the meniscus.

Units of Measure

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Mass and Weight How is he floating? One of the many interesting things about travel in outer space is the idea of weightlessness. If something is not fastened down, it will float in mid-air. Early astronauts learned that weightlessness had bad effects on bone structure. If there was no pressure on the legs, those bones would begin to lose mass. Weight provided by gravity is needed to maintain healthy bones. Specially designed equipment is now a part of every space mission, so the astronauts can maintain good body fitness. Mass is a measure of the amount of matter that an object contains. The mass of an object is made in comparison to the standard mass of 1 kilogram. The kilogram was originally defined as the mass of 1 L of liquid water at 4°C (volume of a liquid changes slightly with temperature). In the laboratory, mass is measured with an electric balance which must be calibrated with a standard mass so that its measurements are accurate. Other common units of mass are the gram and the milligram. A gram is 1/1000th of a kilogram, meaning that there are 1000 g in 1 kg. A milligram is 1/1000th of a gram, so there are 1000 mg in 1 g. Mass is often confused with the term weight. Weight is a measure of force that is equal to the gravitational pull on an object. The weight of an object is dependent on its location. On the moon, the force due to gravity is about one sixth that of the gravitational force on Earth. Therefore, a given object will weigh six times more on Earth than it does on the moon. Since mass is dependent only on the amount of matter present in an object, mass does not change with location. Weight measurements are often made with a spring scale by reading the distance that a certain object pulls down and stretches a spring.

Temperature and Temperature Scales Touch the top of the stove after it has been on, and it feels hot. Hold an ice cube in your hand and it feels cold. Why? The particles of matter in a hot object are moving much faster than the particles of matter in a cold object. An object’s kinetic energy is the energy due to motion. The particles of matter that make up the hot stove have a greater amount of kinetic energy than those in the ice cube. Temperature is a measure of the average kinetic energy of the particles in matter. In everyday usage, temperature indicates a measure of how hot or cold an object is. Temperature is an important parameter in chemistry. When a substance changes from solid to liquid, it is because there was an increase in the temperature of the material. Chemical reactions usually proceed faster if the temperature is increased. Many unstable materials (such as enzymes) will be viable longer at lower temperatures.

Units of Measure

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Temperature Scales The first thermometers were glass and contained alcohol, which expanded and contracted as the temperature changed. The German scientist, Daniel Gabriel Fahrenheit, used mercury in the tube. The Fahrenheit scale was first developed in 1724 and tinkered with for some time after that. The main problem with this scale is the arbitrary definitions of temperature. The freezing point of water was defined as 32°F and the boiling point as 212°F. The Fahrenheit scale is typically not used for scientific purposes.

Daniel Gabriel Fahrenheit The Celsius scale of the metric system is named after Swedish astronomer Anders Celsius (1701-1744). The Celsius scale sets the freezing point and boiling point of water at 0°C and 100°C respectively. The distance between those two points is divided into 100 equal intervals, each of which is one degree. Another term sometimes used for the Celsius scale is “centigrade” because there are 100 degrees between the freezing and boiling points of water on this scale. However, the preferred term is “Celsius.” Anders Celsius

The Kelvin temperature scale is named after Scottish physicist and mathematician Lord Kelvin (1824-1907). It is based on molecular motion, with the temperature of 0 K, also known as absolute zero, being the point where all molecular motion ceases. The freezing point of water on the Kelvin scale is 273.15 K, while the boiling point is 373.15 K. Notice that here is no “degree” used in the temperature designation. Unlike the Fahrenheit and Celsius scales where temperatures are referred to as “degrees F” or “degrees C,” we simply designated temperatures in the Kelvin scale as kelvins.

Lord Kelvin As can be seen by the 100 kelvin difference between the two, (boiling points and freezing point), a change of one degree on the Celsius scale is equivalent to the change of one kelvin on the Kelvin scale. Converting from one scale to another is easy, as you simply add 273 to go from Celsius to Kelvin or subtract 273 to go from Kelvin to Celsius.

Metric System

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Many properties of matter are quantitative; that is, they are associated with numbers. When a number represents a measured quantity, the unit of that quantity must always be specified. To say that the length of a pencil is 17.5 is meaningless; however, saying it is 17.5 cm specifies the length. The units used for scientific measurements are those of the metric system. The metric system was developed in France during the late 1700s and is the most common form of measurement in the world. There are a few countries, The United States of America, that do not follow the metric system; we use the English system. Over the years the use of the metric system has become more common; just look at a can of soda, there are indications of the metric system. Metric Prefixes Conversions between metric system units are straightforward because the system is based on powers of ten. For example, meters, centimeters, and millimeters are all metric units of length. There are 10 millimeters in 1 centimeter and 100 centimeters in 1 meter. Metric prefixes are used to distinguish between units of different size. These prefixes all derive from either Latin or Greek terms.

The tables above lists the most common metric prefixes and their relationship to the central unit that has no prefix. There are a couple of odd little practices with the use of metric abbreviations. Most abbreviations are lower-case. We use “m” for meter and not “M”. However, when it comes to volume, the base unit “liter” is abbreviated as “L” and not “l”. So we would write 3.5 milliliters as 3.5 mL. As a practical matter, whenever possible you should express the units in a small and manageable number. If you are measuring the weight of a material that weighs 6.5 kg, this is easier than saying it weighs 6500 g or 0.65 dag. All three are correct, but the kg units in this case make for a small and easily managed number. However, if a specific problem needs grams instead of kilograms, go with the grams for consistency.

Can of Soda showing both English (oz) & Metric (mL) units

Metric System

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Converting (Dimensional Analysis) How can a number of track laps be converted to a distance in meters? You are training for a 10-kilometer run by doing laps on a 400-meter track. You ask yourself “How many times do I need to run around this track in order to cover ten kilometers?” (More than you realize & one of the many reasons I don’t run). By using dimensional analysis, you can easily determine the number of laps needed to cover the 10 k distance Conversion Factors Many quantities can be expressed in several different ways. The English of system measurement of 4 cups is also equal to 2 pints, 1 quart, and 0.25 of a gallon.

4 cups = 2 pints or 1 quart or 0.25 gallon

Notice that the numerical component of each quantity is different, while the actual amount of material that it represents is the same. That is because the units are different. We can establish the same set of equalities for the metric system:

1 meter = 10 decimeters or 100 centimeters or 1000 millimeters The metric system’s use of powers of 10 for all conversions makes this quite simple. Whenever two quantities are equal, a ratio can be written that is numerically equal to 1. Using the metric examples above: 1m = 100cm = 1m = 1 100cm 1000mm 1m The 1 m/100 cm is called a conversion factor. A conversion factor is a ratio of equivalent measurements. Because both 1 m and 100 cm represent the exact same length, the value of the conversion factor is 1. The conversion factor is read as “1 meter per 100 centimeters”. Other conversion factors from the cup measurement example can be: 4 cups = 2 pints = 1 quart = 1 2 pints 1 quart ¼ gallon Since the numerator and denominator represent equal quantities in each case, all are valid conversion factors. Scientific Dimensional Analysis Conversion factors are used in solving problems in which a certain measurement must be expressed with different units. When a given measurement is multiplied by an appropriate conversion factor, the numerical value changes, but the actual size of the quantity measured remains the same. Dimensional analysis is a technique that uses the units (dimensions) of the measurement in order to correctly solve problems. Dimensional analysis is best illustrated with an example.

Metric System

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Set-Up # unit looking for = Given x Unknown = 1 Conversion factor The unit you are looking for MUST match the unit for your unknown. The unit for your given MUST match the unit on the conversion factor Sample Problem 1: How many seconds are in a day? Step 1: List the known quantities and plan the problem. Known • 1 day = 24 hours • 1 hour = 60 minutes • 1 minute = 60 seconds Unknown • 1 day =? seconds The known quantities above represent the conversion factors that we will use. The first conversion factor will have day in the denominator so that the “day” unit will cancel. The second conversion factor will then have hours in the denominator, while the third conversion factor will have minutes in the denominator. As a result, the unit of the last numerator will be seconds, and that will be the units for the answer. Step 2: Calculate # secs = 1 day x 24 hours x 60 min x 60 sec = 86,400 sec 1 day 1 hour 1 min Applying the first conversion factor, the “day” unit cancels and 1 x 24 = 24. Applying the second conversion factor, the “hour” unit cancels and 24 x 60 = 1440. Applying the third conversion factor, the “min” unit cancels and 1440 x 60 = 86,400. The unit that remains is “s” for seconds. Step 3: Think about your result. Seconds is a much smaller unit of time than a day, so it makes sense that there are a very large number of seconds in one day.

Metric System

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Metric Unit Conversions The metric system’s many prefixes allow quantities to be expressed in many different units. Dimensional analysis is useful to convert from one metric system unit to another. Sample Problem 2: A particular experiment requires 120 mL of a solution. The teacher knows that he will need to make enough solution for 40 experiments to be performed throughout the day. How many liters of solution should he prepare? Step 1: List the known quantities and plan the problem. Known • 1 experiment requires 120 mL • 1 L = 1000 mL Unknown • L of solution for 40 experiment Since each experiment requires 120 ml of solution and the teacher needs to prepare enough for 40 experiments, multiply 120 by 40 to get 4800 mL of solution needed. Now you must convert ml to L by using a conversion factor. Step 2: Calculate # L = 4800 mL x 1 L = 4.8 L 1000 mL Note that conversion factor is arranged so that the mL unit is in the denominator and thus cancels out, leaving L as the remaining unit in the answer. Step 3: Think about your result. A liter is much larger than a milliliter, so it makes sense that the number of liters required is less than the number of milliliters.

Metric System

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Two-Step Metric Unit Conversions Some metric conversion problems are most easily solved by breaking them down into more than one step. When both the given unit and the desired unit have prefixes, one can first convert to the simple (un-prefixed) unit, followed by a conversion to the desired unit. An example will illustrate this method. Sample Problem 3: Two-Step Metric Conversion Convert 4.3 km to cm. Step 1: List the known quantities and plan the problem. Known • 1 m = 100 cm • 1 km = 1000 m Unknown • 4.3 cm =? km You may need to consult a table for the multiplication factor represented by each metric prefix. First convert cm to m, followed by a conversion of m to km. Step 2: Calculate # of cm = 4.3 km x 1000 m x 100 cm = 430,000 cm 1 km 1 m Each conversion factor is written so that unit of the denominator cancels with the unit of the numerator of the previous factor. Step 3: Think about your result. A centimeter is a smaller unit of length than a kilometer, so the answer in centimeters is larger than the number of kilometers given.

Metric System

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The Magic Sentence There are many tools that can be used to make your life in chemistry easier; one is the magic sentence to learn the metric prefixes and their values. And it goes like this:

King Hector Died Monday Drinking Chocolate Milk

King (kilo) Hector (hector)

Died (deca/deka) Monday (meter/gram/liter)

Drinking (deci) Chocolate (centi)

Milk (milli)

Scientific Notation How far is the Sun from Earth? Astronomers are used to really big numbers. While the moon is only 406,697 km from earth at its maximum distance, the sun is much further away (150 million km). Proxima Centauri, the star nearest the earth, is 39, 900, 000, 000, 000 km away and we have just started on long distances. On the other end of the scale, some biologists deal with very small numbers: a typical fungus could be as small as 30 μmeters (0.000030 meters) in length and a virus might only be 0.03 μmeters (0.00000003 meters) long. Scientific Notation Scientific notation is a way to express numbers as the product of two numbers: a coefficient and the number 10 raised to a power. It is a very useful tool for working with numbers that are either very large or very small. As an example, the distance from Earth to the Sun is about 150,000,000,000 meters –a very large distance indeed. In scientific notation, the distance is written as 1.5 x 1011 m. The coefficient is the 1.5 and must be a number greater than or equal to 1 and less than 10. The power of 10, or exponent, is 11 because you would have to multiply 1.5 by 1011 to get the correct number. Scientific notation is sometimes referred to as exponential notation. When working with small numbers, less than zero, we use a negative exponent. So 0.1 meters is 1 x 10-1 meters. Note the use of the leading zero (the zero to the left of the decimal point). That digit is there to help you see the decimal point more clearly. The figure 0.01 is less likely to be misunderstood than .01 where you may not see the decimal. When working with large numbers, greater than zero, we use a positive exponent. So 10 meters is 1.0 x 101. The exponent represents the number of places the decimal point moves, not the number of zeroes in the number. If you move the decimal place to the left you add to the exponent the same number of places you moved; if you are moving the decimal to the right you subtract from the exponent the same number of places you moved. This is often referred to as LARS, (left – add and right – subtract).

Summer 2017 Metrics Honors Chemistry

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Working with SI (metric) Units For each of the following commonly used measurements, indicate its symbol.

_____ liter

_____ milliliter

_____ meter

_____ centimeter

_____ kilometer

_____ millimeter

_____ gram

_____ kilogram

_____ centigram

_____ milligram

_____ second

_____ milliseconds Use the symbols to complete the following sentences with the most appropriate unit.

1. The mass of a bowling ball is 7.25 _____.

2. The lung capacity of an average man is about 4.8 _____.

3. The length of a housefly is about 1 _____.

4. The average length of time it takes to blink is about 2 _____.

5. One teaspoon of cough syrup has a volume of 5 _____.

6. The length of a human’s small intestine is about 6.25 _____.

7. The mass of a paperclip is about 1 _____.

8. When resting, the average adult’s heart beats once every 1.2 _____.

9. The mass of a flea is about 0.5 _____.

10. The distance between San Antonio and Dallas is approximately 440 _____.

Write the abbreviation for the following common metric prefixes:

1. Kilo ___________ 2. Hecto _________ 3. Deca/Deka ___________ 4. Meter ___________ 5. Gram ___________ 6. Liter ____________ 7. Deci _____________ 8. Centi ___________ 9. Milli ____________

Summer 2017 Metrics Honors Chemistry

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Dimensional Analysis

Convert the following 1. 35 daL = _________________dL

2. 950 g = __________________ kg

3. 275 mm = ________________cm

4. 1,000 L = _________________ kL

5. 1,000 mL _________________ L

6. 0.17 cm = ________________ hm

7. 2.65 km = ________________ dm

8. 1.0 km = __________________ mm

9. 18 dag = __________________ cg

10. 4,500 mg __________________ g

11. 25 cm = __________________ mm

12. 0.005 kg = ________________ dag

13. 0.075 m = _________________ cm

14. 15 g = ____________________ mg

15. 0.987 kL = _________________ hL

16. 1.281 mm = _________________m

17. 12.07 hg = __________________ dag

18. 1625.0 cm = _________________ m

19. 3017.36 mg = ________________ dg

20. 71.18 L = ____________________ cL

Summer 2017 Scientific Notation Honors Chemistry

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Write the number(s) given in each problem using scientific notation. Don’t forget the unit.

1. The human eye blinks an average of 4,200,000 times a year. _________________________________________

2. A computer processes a certain command in 15 nanoseconds. (A nanosecond is one billionth of a second.) In decimal form, this number is 0. 000 000 015 ____________________________________________

3. There are 60,000 miles (97,000 km) in blood vessels in the human body. _____________ miles ___________km

4. The highest temperature produced in a laboratory was 920,000,000 F (511,000,000 C) at the Tokomak Fusion Test Reactor in Princeton, NJ, USA. _______________________ oF _______________________________oC

5. The mass of a proton is 0.000 000 000 000 000 000 000 001 673 grams. _____________________________

6. The mass of the sun is approximately 1,989,000,000,000,000,000,000,000,000,000,000 grams.______________

7. The cosmos contains approximately 50,000,000,000 galaxies. _______________________________________

8. A plant cell is approximately 0.00001276 meters wide. ____________________________________________

Write the number(s) given scientific notation in standard form. Don’t forget the unit.

9. The age of earth is approximately 4.5 X 109 years. _________________________________________________________________________________________

10. The weight of one atomic mass unit (a.m.u.) is 1.66 x 10-27 kg. _________________________________________________________________________________________

Uncertainty in Measurement

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How do police officers identify criminals? After a bank robbery has been committed, police will ask witnesses to describe the robbers. They will usually get some answer such as “medium height.” Others may say “between 5 foot 8 inches and 5 foot 10 inches.” In both cases, there is a significant amount of uncertainty about the height of the criminals. Measurement Uncertainty There are two types of numbers in the scientific world, exact numbers and inexact numbers. Exact numbers are numbers whose values are known exactly. For example, there are 12 in a dozen and 1000 grams in 1 kg. Inexact numbers have values with some uncertainty. If you give 10 students each a dime and tell them to use a triple beam balance to obtain the mass of their dime, you will slightly varying masses. The reason for the differences may be due to equipment error, the balances not being calibrated equally, or human error, reading the balance wrong. Uncertainties always exist in measured quantities. The amount of uncertainty depends both upon the skill of the measurer and upon the quality of the measuring tool. While some balances are capable of measuring masses only to the nearest 0.1 g, other highly sensitive balances are capable of measuring to the nearest 0.001 g or even better. Many measuring tools such as rulers and graduated cylinders have small lines which need to be carefully read in order to make a measurement. The figure to the left shows two rulers making the same measurement of an object (indicated by the arrow). With either ruler, it is clear that the length of the object is between 2 and 3 cm. The bottom ruler contains no millimeter markings. With that ruler, the tenths digit can be estimated and the length may be reported as 2.5 cm. However, another person may judge that the measurement is 2.4 cm or perhaps 2.6 cm. While the 2 is known for certain, the value of the tenths digit is uncertain.

The top ruler contains marks for tenths of a centimeter (millimeters). Now the same object may be measured as 2.55 cm. The measurer is capable of estimating the hundredths digit because he can be certain that the tenths digit is a 5. Again, another measurer may report the length to be 2.54 cm or 2.56 cm. In this case, there are two certain digits (the 2 and the 5), with the hundredths digit being uncertain. Clearly, the top ruler is a superior ruler for measuring lengths as precisely as possible.

Precision and Accuracy The terms precision and accuracy are often used in discussing the uncertainties of measured values. Precision is the measure of how closely individual measurements agree with one another. Accuracy refers to how closely individual measurements agree with the correct or “true” value. Refer to figure above for a visual representation of precision and accuracy.

Uncertainty in Measurement

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Significant Figures

How fast do you drive? As you enter the town of Jacinto City, Texas, the sign below tells you that the speed limit is 30 miles per hour. But what if you happen to be driving 31 miles an hour? Are you in trouble? Probably not, because there is a certain amount of leeway built into enforcing the regulation. Most speedometers do not measure the vehicle speed very accurately and could easily be off by a mile or so (on the other hand, radar measurements are much more accurate). So, a couple of miles/hour difference won’t matter that much. Just don’t try to stretch the limits any further unless you want a traffic ticket.

The significant figures in a measurement consist of all the certain digits in that measurement plus one uncertain or estimated digit. In the ruler illustration below, the bottom ruler gives a length with 2 significant figures, while the top

ruler gives a length with 3 significant figures. In a correctly reported measurement, the final digit is significant but not certain. Insignificant digits are not reported. With either ruler, it would not be possible to report the length as 2.553 cm as there is no possible way that the thousandths digit could be estimated. The 3 is not significant and would not be reported.

When you look at a reported measurement, it is necessary to be able to count the number of significant figures. The table below details the rules for determining the number of significant figures in a reported measurement. For the examples in the table below, assume that the quantities are correctly reported values of a measured quantity.

Significant Figure Rules

Rule Examples

1. All nonzero digits in a measurement are significant

A. 237 has three significant figures. B. 1.897 has four significant figures.

2. Zeroes that appear between other nonzero digits are always significant.

A. 39,004 has five significant figures. B. 5.02 has three significant figures

3. Zeroes that appear in front of all of the nonzero digits are called left-end zeroes. Left-end zeroes are never significant

A. 0.008 has one significant figure. B. 0.000416 has three significant figures.

4. Zeroes that appear after all nonzero digits are called right-end zeroes. Right-end zeroes in a number that lacks a decimal point are not significant.

A. 140 has two significant figures. B. 75,210 has four significant figures.

5. Right-end zeroes in a number with a decimal point are significant. This is true whether the zeroes occur before or after the decimal point.

A. 620.0 has four significant figures. B. 19.000 has five significant figures

Uncertainty in Measurement

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It needs to be emphasized that to say a certain digit is not significant does not mean that it is not important or can be left out. Though the zero in a measurement of 140 may not be significant, the value cannot simply be reported as 14. An insignificant zero functions as a placeholder for the decimal point. When numbers are written in scientific notation, this becomes more apparent. The measurement 140 can be written as 1.4 × 102 with two significant figures in the coefficient. For a number with left-end zeroes, such as 0.000416, it can be written as 4.16 × 10−4 with 3 significant figures. In some cases, scientific notation is the only way to correctly indicate the correct number of significant figures. In order to report a value of 15,000,000 with four significant figures, it would need to be written as 1.500 × 107. The right-end zeroes after the 5 are significant. The original number of 15,000,000 only has two significant figures. Adding and Subtraction Significant Figures For addition and subtraction, look at the decimal portion (i.e., to the right of the decimal point) of the numbers ONLY. Here is what to do:

1. Count the number of significant figures in the decimal portion of each number in the problem. (The digits to the left of the decimal place are not used to determine the number of decimal places in the final answer.)

2. Add or subtract in the normal fashion.

3. Round the answer to the LEAST number of places in the decimal portion of any number in the

problem. Multiplying and Dividing Significant Figures The following rule applies for multiplication and division:

1. The LEAST number of significant figures in any number of the problem determines the number of significant figures in the answer.

2. This means you MUST know how to recognize significant figures in order to use this rule.

Uncertainty in Measurement

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Density

One of the ways a scientist identifies a substance is by calculating its density. Density is defined as the mass of an object in a given unit of volume. This means that the property of density tells how tightly matter is packed in a substance. You have probably heard of the famous riddle, “Which weighs more, a pound of feathers or a pound of lead?” At first many people say, a pound of lead. But the answer is that they weigh the same (one pound each). This riddle illustrates the physical property of matter called density. The density of lead is much greater than the density of feathers. A pound of lead would be a small cube, while a pound of feathers would be in a much larger box. Another way of saying this is that lead has more matter packed in a smaller space than the feathers have. What is Density? The idea of density can be expressed in mathematical terms. The formula for density is: density = mass divided by volume (d = m/v). So, density is found by dividing mass of an object by its volume. The units for density are usually grams per cubic centimeter (g/cm3) or grams per milliliter (g/mL). Mass is the amount of matter in an object, measured with a balance in the base unit of grams; however volume is the amount of space an object occupies and is measured in the liquid base unit as milliliters (mL) and solid base unit of cubic centimes (cm3) . One milliliter is equal to one cubic centimeter. For example, the mass of an object is 30 grams and its volume is 15 milliliters. We find the density of the object by dividing 15 into 30. The density would be recorded as 2 grams per milliliters or 2 g/mL.

Here is the same example using the proper set up and math:

D = m V D = ? D = 30 g . m = 30 g 15mL V = 15 mL D = 2.00 g/mL

Uncertainty in Measurement

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Water Displacement Many of the solid objects we measure in class have unusual or small shapes. Therefore, we use a method called water displacement to measure the objects volume. The process of this method requires a graduated cylinder to be filled with a set volume of water, the object is then carefully slid into the graduated cylinder, and the difference in water is recorded as the volume of the object. For example, the graduated cylinder is filled to 50 milliliters, the object is added and the water moves to 100 milliliters. We find the object’s volume by subtracting the initial volume of water, 50 mL, from the volume of the water with the object, 100 mL; the objects volume is 50 mL. Using conversions, you can determine the object as having a volume of 50 cm3. Uses of Density The density of any particular substance is always the same, regardless of the size of the object being measured. Because of this, density is used to identify substances. For example, gold has density of 19.32 g/cm3, copper has a density of 8.9 g/cm3, and water has a density of 1 g/mL. So, how can this be used? An example can be seen with the two metals, silver and polished aluminum. They both look alike and have many common properties, so how can we tell them both apart? We measure their densities by first finding their mass and volumes and plugging them into our formula for density and then comparing our answer to the known densities of the metals. Aluminum has a density of 2.7 g/cm3and silver has a much heavier density. You can also use density to determine the amount of gold found in a piece of jewelry. Gold alone is too soft to use in the making of jewelry so it is often mixed with copper to make it stronger. This mixture is called an alloy. The gold alloy is not worth as much as pure gold. To determine how much copper is in the gold alloy, you must first find the mass of the jewelry. Then, measure the volume of the jewelry using the water displacement method due to its irregular shape. When the mass is divided by volume, density can be determined. If a piece of jewelry is 50% copper and 50% gold, its density would be 12.22 g/cm3. If its density is less than this, it would have more copper in it than gold and the value would be lower. If its density is more than this, it would have more gold in it than copper and the value would be higher. The densities of liquid can show how much matter is dissolved in them. For example, the liquid in a car battery is a mixture of water and sulfuric acid. The density of this liquid is about 1.3 g/mL. When a car battery is in good condition, the liquid is at its highest density. As the battery ages and loses its ability to produce electricity, the density of the water drops. The condition of the battery can be determined by measuring the liquid's density. The higher the density, the better the battery's condition. Service stations have a tube with a float in it called a hydrometer. This device measures the density of the battery liquid. There is a rubber bulb on one end of the tube that the attendant squeezes to draw battery liquid into the device and the float floats in the liquid. In a more dense liquid, more of the float remains above the surface. The float rides deeper in less dense liquids. Marks on the float tell what the liquid's density is. Low density would suggest a bad battery. Hydrometers can also be used to determine the densities of other liquids such as milk sugar, alcohol, or pollutants in water.

final volume of water

with object 100 mL

object

difference in the water’s volume

before and after the object

is 50 mL

initial volume of water 50 mL

Uncertainty in Measurement

15

Another use of density can be found in the sports gym. An athletic trainer can determine the percentage of body fat in an athlete's body. The mass of the athlete is first determined on a scale. He or she is then immersed in a tub of water to determine their volume. The density of the athlete is calculated. If the percent of the body fat is too high, the trainer will recommend a diet and exercise program. Densities also show which objects will float in various liquids. An object that can float is often called buoyant. Buoyancy is a simple way of relating the density of one object to another, since the object with greater density will sink and the object with the smaller density will float. In other words, the rule is objects of lower density will float on liquids of higher density. For example, most dry wood is less dense than water, since it has many air pockets. A block of dry wood will, therefore, float in water. If the wood becomes water soaked, the air in the wood is replaced with water. The wood then becomes denser than water and will sink. Density applies to all forms of matter. Seawater is denser than fresh water. Cold air is denser than warm air. Mercury, a liquid, is denser than steel a hard, tough, solid. As you can see, density is an important physical property of matter.

Summer 2017 Significant Figures Honors Chemistry

5

1. State the number of significant figures in each

measurement. a. 734 grams b. 82.400 meters c. 92,000°C d. 0.003 second e. 607 liters

f. 1 × 10-4 hertz

2. Round the number in the first column to the number of significant figures stated in each column.

Number Four significant figures

Three significant figures

Two significant figures

One significant figure

84.631 0.94500 7.95310

2,058,268 3. Perform the following operations. Round the answers to the appropriate number of significant figures.

Label the units. a. 8.2 cm × 6.08 cm × 15.0 cm

b. 34.8 meter / 3.048 seconds

c. 23.4°C – 8.4°C

d. 65.48 g + 3.0 g + 0.882 g + 26.46 g

4. Write the following numbers to 3 significant figures; round or convert to scientific notation if needed

34,534 m 0.2323 m 3,004 m 0.320 m

4,000 m 0.0033 m 400.1 m 0.0001 m

300.0 m 15.04 m 30.00 m 0.000004 m

Classification of Matter

13

Physical Properties of Matter Let’s begin our study of chemistry by examing some fundamental ways in which matter is classified and described. There are two principle ways of classifying matter: its physical state and its composition (chemical).

Both of these men are skiing, but the man on the left is skiing on snow while the man on the right is skiing on sand. Snow and sand are both kinds of matter, but they have different properties. What are some ways snow and sand differ? One difference is the temperature at which they melt. Snow melts at 0°C, whereas sand melts at about 1600°C! The temperature at which something melts is its melting point. Melting point is just one of many physical properties of matter. Extensive and Intensive Properties How much is twenty dollars really worth?

I agree to mow someone’s lawn for twenty dollars (it’s a fairly big yard). When they pay me, they give me a $20 bill. It doesn’t matter whether the bill is brand new or old, dirty, and wrinkled – all these bills have the same value of $20. If I want more $20 bills, I have to mow more lawns. I can’t say, “This particular bill is actually worth more than $20.” To have more money, I have to put in more work. Extensive Properties Some properties of matter depend on the size of the sample, while some do not. An extensive property is a property that depends on the amount of matter in a sample. The mass of an object is a measure of the amount of matter that an object contains. A small sample of a certain type of matter will have a small mass, while a larger sample will have a greater mass. Another extensive property is volume. The volume of an object is a measure of the space that is occupied by that object.

The figure below illustrates the extensive property of volume. The pitcher and glass both contain milk. The pitcher holds approximately two quarts and the glass will hold about 8 ounces of milk. The same milk is in each container. The only difference is the amount of milk contained in the glass and in the pitcher

Classification of Matter

14

Intensive Properties The electrical conductivity of a substance is a property that depends only on the type of substance. Silver, gold, and copper are excellent conductors of electricity, while glass and plastic are poor conductors. A larger or smaller piece of glass will not change this property. An intensive property is a property of matter that depends only on the type of matter in a sample and not on the amount. Other intensive properties include color, temperature, density, and solubility. The copper wire shown in the picture below has a certain electrical conductivity. You could cut off the small end sticking out and it would have the same conductivity as the entire long roll of wire shown here. The conductivity is a property of the copper metal itself, not of the length of the wire. Physical Properties of Matter Why are drag car standards constantly reinforced?

Drag racing is a highly competitive (and expensive) sport. There are a variety of classes of vehicles, ranging from stock classes (depending on car weight, engine size, and degree of engine modification) all the way up to the Top Fuel class with weights of over two thousand pounds and capable of top speeds of well over 300 miles/hour at the end of the quarter-mile. The standards for each class are well-defined and frequent checks are made of engine dimensions and components to insure that the rules are followed.

A physical property is a characteristic of a substance that can be observed or measured without changing the identity of the substance. Silver is a shiny metal that conducts electricity very well. It can be molded into thin sheets, a property called malleability. Salt is dull and brittle and conducts electricity when it has been dissolved into water, which it does quite easily. Physical properties of matter include color, hardness, malleability, solubility, electrical conductivity, density, melting points, and boiling points.

For the elements, color does not vary much from one element to the next. The vast majority of elements are colorless, silver, or gray. Some elements do have distinctive colors: sulfur and chlorine are yellow, copper is (of course) copper-colored and elemental bromine is red.

Density can be a very useful parameter for identifying an element. Of the materials that exist as solids at room temperature, iodine has a very low density compared to zinc, chromium and tin. Gold has a very high density, as does platinum.

Hardness helps determine how an element (especially a metal) might be used. Many elements are fairly soft (silver and gold, for example) while others (such as titanium, tungsten, and chromium) are much harder. Carbon is an interesting example of hardness. In graphite (the “lead” found in pencils) the carbon is very soft, while the carbon in a diamond is roughly seven times as hard.

Classification of Matter

15

Chemical Properites of Matter Chemical properties are properties that can be measured or observed only when matter undergoes a change to become an entirely different kind of matter. For example, the ability of iron to rust can only be observed when iron actually rusts. When it does, it combines with oxygen to become a different substance called iron oxide. Iron is very hard and silver in color, whereas iron oxide is flakey and reddish brown. Besides the ability to rust, other chemical properties include reactivity and flammability.

Reactivity is the ability of matter to combine chemically with other substances. Some kinds of matter are extremely reactive; others are extremely unreactive. For example, the metal magnesium is very reactive, even with water. When a pea-sized piece of magnesium is added to a small amount of water, it reacts explosively. In contrast, noble gases such as helium almost never react with any other substances. The chart below shows the reactivity of several different metals. The metals range from very reactive to very unreactive.

Flammability is the ability of matter to burn. When matter burns, it combines with oxygen and changes to different substances. Wood is an example of flammable matter. When wood burns, it changes to ashes, carbon dioxide, water vapor, and other gases. You can see ashes in the wood fire pictured to the right. The gases are invisible.

Density One of the ways a scientist identifies a substance is by calculating its density. Density is defined as the mass of an object in a given unit of volume. This means that the property of density tells how tightly matter is packed in a substance. You have probably heard of the famous riddle, “Which weighs more, a pound of feathers or a pound of lead?” At first many people say, a pound of lead. But the answer is that they weigh the same (one pound each). This riddle illustrates the physical property of matter called density. The density of lead is much greater than the density of feathers. A pound of lead would be a small cube, while a pound of feathers would be in a much larger box. Another way of saying this is that lead has more matter packed in a smaller space than the feathers have. What is Density? The idea of density can be expressed in mathematical terms. The formula for density is: density = mass divided by volume (d = m/v). So, density is found by dividing mass of an object by its volume. The units for density are usually grams per cubic centimeter (g/cm3) or grams per milliliter (g/mL). Mass is the amount of matter in an object, measured with a balance in the base unit of grams; however volume is the amount of space an object occupies and is measured in the liquid base unit as milliliters (mL) and solid base unit of cubic centimes (cm3) . One milliliter is equal to one cubic centimeter. For example, the mass of an object is 30 grams and its volume is 15 milliliters. We find the density of the object by dividing 15 into 30. The density would be recorded as 2 grams per milliliters or 2 g/mL.

Classification of Matter

16

Here is the same example using the proper set up and math:

D = m V D = ? D = 30 g . m = 30 g 15mL V = 15 mL D = 2.00 g/mL Water Displacement Many of the solid objects we measure in class have unusual or small shapes. Therefore, we use a method called water displacement to measure the objects volume. The process of this method requires a graduated cylinder to be filled with a set volume of water, the object is then carefully slid into the graduated cylinder, and the difference in water is recorded as the volume of the object. For example, the graduated cylinder is filled to 50 milliliters, the object is added and the water moves to 100 milliliters. We find the object’s volume by subtracting the initial volume of water, 50 mL, from the volume of the water with the object, 100 mL; the objects volume is 50 mL. Using conversions, you can determine the object as having a volume of 50 cm3.

final volume of water

with object

100 L object

difference in the water’s

volume before and

after the bj t i 50

initial volume of water 50 mL

Classification of Matter

17

Uses of Density The density of any particular substance is always the same, regardless of the size of the object being measured. Because of this, density is used to identify substances. For example, gold has density of 19.32 g/cm3, copper has a density of 8.9 g/cm3, and water has a density of 1 g/mL. So, how can this be used? An example can be seen with the two metals, silver and polished aluminum. They both look alike and have many common properties, so how can we tell them both apart? We measure their densities by first finding their mass and volumes and plugging them into our formula for density and then comparing our answer to the known densities of the metals. Aluminum has a density of 2.7 g/cm3and silver has a much heavier density. You can also use density to determine the amount of gold found in a piece of jewelry. Gold alone is too soft to use in the making of jewelry so it is often mixed with copper to make it stronger. This mixture is called an alloy. The gold alloy is not worth as much as pure gold. To determine how much copper is in the gold alloy, you must first find the mass of the jewelry. Then, measure the volume of the jewelry using the water displacement method due to its irregular shape. When the mass is divided by volume, density can be determined. If a piece of jewelry is 50% copper and 50% gold, its density would be 12.22 g/cm3. If its density is less than this, it would have more copper in it than gold and the value would be lower. If its density is more than this, it would have more gold in it than copper and the value would be higher. The densities of liquid can show how much matter is dissolved in them. For example, the liquid in a car battery is a mixture of water and sulfuric acid. The density of this liquid is about 1.3 g/mL. When a car battery is in good condition, the liquid is at its highest density. As the battery ages and loses its ability to produce electricity, the density of the water drops. The condition of the battery can be determined by measuring the liquid's density. The higher the density, the better the battery's condition. Service stations have a tube with a float in it called a hydrometer. This device measures the density of the battery liquid. There is a rubber bulb on one end of the tube that the attendant squeezes to draw battery liquid into the device and the float floats in the liquid. In a more dense liquid, more of the float remains above the surface. The float rides deeper in less dense liquids. Marks on the float tell what the liquid's density is. Low density would suggest a bad battery. Hydrometers can also be used to determine the densities of other liquids such as milk sugar, alcohol, or pollutants in water. Another use of density can be found in the sports gym. An athletic trainer can determine the percentage of body fat in an athlete's body. The mass of the athlete is first determined on a scale. He or she is then immersed in a tub of water to determine their volume. The density of the athlete is calculated. If the percent of the body fat is too high, the trainer will recommend a diet and exercise program. Densities also show which objects will float in various liquids. An object that can float is often called buoyant. Buoyancy is a simple way of relating the density of one object to another, since the object with greater density will sink and the object with the smaller density will float. In other words, the rule is objects of lower density will float on liquids of higher density. For example, most dry wood is less dense than water, since it has many air pockets. A block of dry wood will, therefore, float in water. If the wood becomes water soaked, the air in the wood is replaced with water. The wood then becomes denser than water and will sink. Density applies to all forms of matter. Seawater is denser than fresh water. Cold air is denser than warm air. Mercury, a liquid, is denser than steel a hard, tough, solid. As you can see, density is an important physical property of matter.

Classification of Matter

18

States of Matter In addition to these properties, other physical properties of matter include the state of matter. States of matter include liquid, solid, and gaseous states and they differ in simple observable properties. A liquid has a distinct volume independent of its container but has no specific shape – it can take on the shape of any container. A solid has both a definite shape and a definite volume. A gas, also called a vapor, has no fixed volume or shape; rather it conforms to the volume and shape of its container. The properties of matter can be understood at the molecular level: the figure to the right shows each state of matter at the molecular level. Composition of Matter Most forms of matter that we encounter-for example, the air we breathe (gas), the gas in our cars (liquid) and the sidewalk on which we walk (solid) – are not chemically pure. We can separate matter into different pure substances. Pure substances (substances) are matter that has distinct properties and a composition that does not vary from sample to sample. Water and table salt (sodium chloride, NaCl), the primary components of seawater, are examples of pure substances. All substances are either elements or compounds. Elements cannot be decomposed (broken down) into simpler substances. On the molecular level, each element is composed of a single type of atom. Compounds are substances composed of two or more elements; they contain two or more kinds of atoms. Water, for example, is a compound composed of the elements of hydrogen and oxygen. Mixtures are combinations of two or more substances in which each substance retains its chemical identity. Elements Currently there are 117 known elements and you have to know them all. Just kidding, only the first 20 or so. These 117 elements vary widely in their abundance. For example, only 5 elements – oxygen, silicon, aluminum, iron and calcium – account for over 90% of the earth’s crust. Also, only 3 elements – oxygen, carbon and hydrogen – account for over 90% of the human body. Some of the more common elements are listed below with their chemical symbols. Chemical symbols are abbreviations of a chemical and consist of one or two letters, with the first letter being capitilized. These symbols are mostly derivied from the English name with some from foreign names. All known elements and their symbols are listed on the periodic table of elements – this table will soon be your best friend in chemistry, please be nice.

Classification of Matter

19

Compounds Most elements can interact with other elements to form compounds. Compounds consist of two or more elements, and compounds always have the same elemental composition, that is, elements will combine in whole number ratios, and each compound has its own unique composition. For example, carbon monoxide, CO, consists of one carbon atom and one oxygen atom; whereas carbon dioxide, CO2, consists of one carbon atom and two oxygen atoms. Both carbon monoxide and carbon dioxide are composed of carbon and oxygen, but the number of each element is different. The extra oxygen on carbon dioxide is what makes it distinctly different from carbon monoxide and why CO2 won’t kill you. Mixtures Most of the matter we encounter on a daily basis are mixtures of different substances. As defined earlier, each substance in a mixture retains its own chemical identity and its own properties. In contrast to a pure substance that has a fixed composition, the composition of a mixture can change. For example, you can go into Starbucks and order a coffee black or with cream and sugar or with caramel, mocha and whipped cream, (the best way). The individual substances make up the mixture are called the components of the mixture. Homogeneous mixtures are uniform throughout – you cannot see the individual components, for example, the air you breathe or salt dissolved in water. Homogeneous mixtures are also called solutions, although we assume a solution is a liquid, it can exist in any state. Some mixtures do not have the same composition, properties, and appearance throughout and are called heterogeneous mixtures. Heterogeneous mixtures – such as wood, rocks, and trail mix – vary in texture and appearance; you can identify all the components of the mixture easily. Suspensions are heterogeneous mixtures in which some of the particles settle out of the mixture upon standing. The particles in a suspension are far larger than those of a solution, so gravity is able to pull them down out of the solution. Unlike a solution, the dispersed particles can be separated from the dispersion medium by filtering.

Separation of Mixtures Because each component of a mixture retains its own properties, we can separate a mixture into its components by taking advantage of their properties. There are several techniques we can use to separate mixtures. Magnetism If you have a mixture of sand and iron shavings, you can use a magnet to pull out the iron, leaving the sand.

Chromatography is the separation of a mixture by passing it in solution or suspension or as a vapor (as in gas chromatography) through a medium in which the components move at different rates. Thin-layer chromatography is a special type of chromatography used for separating and identifying mixtures that are or can be colored, especially pigments.

Classification of Matter

20

Distillation is an effective method to separate mixtures comprised of two or more pure liquids. Distillation is a purification process where the components of a liquid mixture are vaporized and then condensed and isolated. In simple distillation, a mixture is heated and the most volatile component vaporizes at the lowest temperature. The vapor passes through a cooled tube (a condenser), where it condenses back into its liquid state. The condensate that is collected is called distillate. In figure to the right, we see several important pieces of equipment. There is a heat source, a test tube with a one-hole stopper attached to a glass elbow and rubber tubing. The rubber tubing is placed into a collection tube which is submerged in cold water. There are other more complicated assemblies for distillation that can also be used, especially to separate mixtures, which are comprised of pure liquids with boiling points that are close to one another.

Evaporation is a technique used to separate out homogenous mixtures where there is one or more dissolved solids. This method drives off the liquid components from the solid components. The process typically involves heating the mixture until no more liquid remains. Prior to using this method, the mixture should only contain one liquid component, unless it is not important to isolate the liquid components. This is because all liquid components will evaporate over time. This method is suitable to separate a soluble solid from a liquid. In many parts of the world, table salt is obtained from the evaporation of sea water. The heat for the process comes from the sun.

Filtration is a separation method used to separate out pure substances in mixtures comprised of particles some of which are large enough in size to be captured with a porous material. Particle size can vary considerably, given the type of mixture. For instance, stream water is a mixture that contains naturally occurring biological organisms like bacteria, viruses, and protozoans. Some water filters can filter out bacteria, the length of which is on the order of 1 micron. Other mixtures, like soil, have relatively large particle sizes, which can be filtered through something like a coffee filter.

Classification of Matter

21

Changes to Matter As with the physical and chemical properties of matter, substances can also undergo changes. Matter can change in two ways – physically or chemically. A physical change to matter changes its physical appearance, but its chemical composition remains the same. A chemical change occurs with the substance is transformed into a chemically different substance, sometimes referred to as a chemical reaction.

Chemical Change Do you like to cook? Cooking is a valuable skill that everyone should have. Whether it is fixing a simple grilled cheese sandwich or preparing an elaborate meal, cooking demonstrates some basic ideas in chemistry. When you bake bread, you mix some flour, sugar, yeast, and water together. After baking, this mixture has been changed to form bread, another substance that has different characteristics and qualities from the original materials. The process of baking has produced chemical changes in the ingredients that result in bread being made. Most of the elements we know about do not exist freely in nature. Sodium cannot be found by itself (unless we prepare it in the laboratory) because it interacts easily with other materials. On the other hand, the element helium does not interact with other elements to any extent. We can isolate helium from natural gas during the process of drilling for oil. A chemical change produces different materials than the ones we started with. One aspect of the science of chemistry is the study of the changes that matter undergoes. If all we had were the elements and they did nothing, life would be very boring (in fact, life would not exist since the elements are what make up our bodies and sustain us). But the processes of change that take place when different chemicals are combined produce all the materials that we use daily. One type of chemical change (already mentioned) is when two elements combine to form a compound. Another type involves the breakdown of a compound to produce the elements that make it up. If we pass an electric current through bauxite (aluminum oxide, the raw material for aluminum metal), we get metallic aluminum as a product.

Electrolytic production of aluminum.

Summer 2017 Density Honors Chemistry

6

1. What is density? ______________________________________________________________________________

2. What is the formula for density?

3. What units are used for density?

4. How are mL and cm3 related? _____________________________________________________________________

_____________________________________________________________________________________________

5. How is density used to determine if your car battery is good? _____________________________________________

_____________________________________________________________________________________________

6. How is density used to identify substances? __________________________________________________________

_____________________________________________________________________________________________

7. If a jeweler was trying to sell you a bracelet that he said was an alloy of 50% copper, how could you be sure he was correct?

For each problem below, write the equation and show your work. Always use units and box or circle your final answer.

8. The density of silver (Ag) is 10.5 g/cm3. Find the mass of Ag that occupies 965 cm3 of space. 9. A 2.75 kg sample of a substance occupies a volume of 250.0 cm3. Find its density in g/cm3.

Summer 2017 Density Honors Chemistry

7

10. Under certain conditions, oxygen gas (O2) has a density of 0.00134 g/mL. Find the volume occupied by 250.0 g of O2 under the same conditions.

11. Find the volume that 35.2 g of carbon tetrachloride (CCl4) will occupy if it has a density of 1.60 g/mL. 12. The density of ethanol is 0.789 g/mL at 20oC. Find the mass of a sample of ethanol that has a volume of 150.0 mL at

this temperature.

13. A rectangular block of lead (Pb) measures 20.0 mm X 30.0 mm X 45.0 mm. If the density of Pb is 11.34 g/cm3, calculate the mass of the block.

14. A cube of gold (Au) has a side length of 1.55 cm. If the sample is found to have a mass of 71.9 g, find the density of

Au. 15. An irregularly-shaped sample of aluminum (Al) is put on a balance and found to have a mass of 43.6 g. The student

decides to use the water-displacement method to find the volume. The initial volume reading is 25.5 mL and, after the Al sample is added, the water level has risen to 41.7 mL. Find the density of the Al sample in g/cm3. (Remember: 1 mL = 1 cm3.)

2017-2018 Honors Chemistry Summer Assignment

Dear Honors Chemistry Student,

Welcome to Honors Chemistry. This class will provide you with the critical thinking and problem-solving skills to be successful in your post-high school life; whether that be college or career. This year we are going to learn lots of chemistry. In order to fit all you need to know in two semesters, we are going to get a head start. Below is a general idea about the class and your summer assignment.

Chemistry is built a lot like math. Each concept we learn is the base for future concepts. It is vital that during the course of the year, you constantly study. At any point you feel lost, confused or overwhelmed, ask for help. Help can be from me, a friend who understands, or even the internet (there are some great websites to help with complicated concepts). In this class, homework is not busy work; homework is designed to help you practice the concept we are learning. The homework will have problems that review what we learned in class and prepare you for any assessment. Please complete your homework on time.

The best part of chemistry is all the labs. We will conduct labs with every unit. It is important that you complete all pre-lab material prior to entering a lab. Reading all the procedures prepares you for what to expect during the lab.

The following pages are your summer assignment for this class. Please complete each worksheet and memorize the elements on the first page (name, symbol, and atomic number) by Wednesday, August 9, 2017. You will be assessed on all summer assignment material on Thursday August 10, 2017.

If you have any questions over the semester, you can email me at Melissa.carlson@guhsdaz.org.

If you are doing your back to school shopping I would recommend the following for chemistry:

1. A thick binder (2-3 inches) 2. Pencil, pens, high-lighters 3. A calculator that can work in scientific notation 4. Spiral notebook for notes 5. Composition notebook for labs

** If you are unable to purchase any of the above items by the second day of school, please let me know so I can have extras on hand for you to use.

I look forward to having a great year with each and every one of you.

Melissa Kestle

Greenway High School

Honors Chemistry

Summer Assignment Information

Please sign up for Kestle’s Honors Chemistry Remind:

Using the phone app: rmd.at/gwhc

Using Text: @gwhc to 81010

Please log onto our Google Classroom Page: code is 51gjaj

Copies of Notes

Videos of Notes

Candle Lab Video and Directions

All Worksheets and Readings for Summer Assignment

Summer Assignment Student Information Page

This page will be placed on the top of the assignment you turn in.

You will only turn in the worksheets and lab, please keep all the readings.

Name: ___________________________________________________________________________

Hour: ____________ Date Turned In: ______________

Score for summer assignment: ________________

Score for you summer lab: _______________

5/20/2016 World's coolest molecules

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World's coolest molecules

August 21, 2014 in Physics / General Physics 

An optical cavity was used to control the wavelength of some of the lasers used for the magneto­optical trap. Credit:Michael Helfenbein

It's official. Yale physicists have chilled the world's coolest molecules.

The tiny titans in question are bits of strontium monofluoride, dropped to 2.5 thousandths of a degree above absolute zero through a laser

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cooling and isolating process called magneto­optical trapping (MOT). They are the coldest molecules ever achieved through directcooling, and they represent a physics milestone likely to prompt new research in areas ranging from quantum chemistry to tests of themost basic theories in particle physics.

"We can start studying chemical reactions that are happening at very near to absolute zero," said Dave DeMille, a Yale physics professorand principal investigator. "We have a chance to learn about fundamental chemical mechanisms."

The research is published this week in the journal Nature.

Magneto­optical trapping has become ubiquitous among atomic physicists in the past generation—but only at the single­atom level. Thetechnology uses lasers to simultaneously cool particles and hold them in place. "Imagine having a shallow bowl with a little molasses init," DeMille explained. "If you roll some balls into the bowl, they will slow down and accumulate at the bottom. For our experiment, themolecules are like the balls and the bowl with molasses is created via laser beams and magnetic fields."

Until now, the complicated vibrations and rotations of molecules proved too difficult for such trapping. The Yale team's unique approachdrew inspiration from a relatively obscure, 1990s research paper that described MOT­type results in a situation where the usual coolingand trapping conditions were not met.

DeMille and his colleagues built their own apparatus in a basement lab. It is an elaborate, multi­level tangle of wires, computers,electrical components, tabletop mirrors, and a cryogenic refrigeration unit. The process uses a dozen lasers, each with a wavelengthcontrolled to the ninth decimal point.

"If you wanted to put a picture of something high­tech in the dictionary, this is what it might look like," DeMille said. "It's deeplyorderly, but with a bit of chaos."

It works this way: Pulses of strontium monofluoride (SrF) shoot out from a cryogenic chamber to form a beam of molecules, which isslowed by pushing on it with a laser. "It's like trying to slow down a bowling ball with ping pong balls," DeMille explained. "You haveto do it fast and do it a lot of times." The slowed molecules enter a specially­shaped magnetic field, where opposing laser beams passthrough the center of the field, along three perpendicular axes. This is where the molecules become trapped.

"Quantum mechanics allows us to both cool things down and apply force that leaves the molecules levitating in an almost perfectvacuum," DeMille said.

The Yale team chose SrF for its structural simplicity—it has effectively just one electron that orbits around the entire molecule. "Wethought it would be best to start applying this technique with a simple diatomic molecule," DeMille said.

The discovery opens the door for further experimentation into everything from precision measurement and quantum simulation toultracold chemistry and tests of the standard model of particle physics.

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More information: Magneto­optical trapping of a diatomic molecule, Nature 512, 286–289 (21 August 2014) DOI:10.1038/nature13634 

Provided by Yale University

"World's coolest molecules" August 21, 2014 http://phys.org/news/2014­08­world­coolest­molecules.html