3rd year OHSP LESSON 1: CHEMISTRY: ITS BEGINNING AND IMPORTANCE - TopicsExpress



          

3rd year OHSP LESSON 1: CHEMISTRY: ITS BEGINNING AND IMPORTANCE TO HUMAN LIFE Chemistry is a branch of science that helps us understand all forms of matter. Like all other sciences, chemistry began in the prehistoric era and flourished in the modern time. The Origins of Chemistry: Where It All Began Time Line in Chemistry Date Person Event 600 B.C. Thales Idea that water is the main form of matter 546 B.C Anaximenes Idea that air is the main form of matter 450 B.C. Empedocles Idea that the four elements – earth, air, fire and water combine in different proportions 420 B.C. Leucippus and Democritus Idea of the atom or the Age of Atomism 1661 Robert Boyle The Sceptical Chymist 1766 H. Cavendish Discovery of hydrogen 1775 A. Lavoisier Discovery of the composition of air 1800 John Dalton Proposed the Atomic Theory 1820 John Jacob Berzelius Devised the modern symbols of elements 1869 Dmitri Mendeleev Periodic Law and designed the Modern Periodic Table of Elements 1886 Eugene Goldstein Naming of cathode rays and discovery of proton 1897 J.J. Thomson Proposed the structure of the atom; discovery of electron 1911 E. Rutherford Proposed the nuclear atom; discovery of a nucleus 1913 Niels Bohr Proposed the energy levels in atoms; Robert Boyle, The Forerunner of Modern Chemistry The modern age of Chemistry dawned in 1661 when Robert Boyle, an English chemist, published his book The Sceptical Chymist. His idea opposed the alchemists’ belief. Instead he proposed that scientists must start from basic principles and that theories about the world have to be proven by a series of experiment. He formulated the law relating volume and pressure. If Robert Boyle laid down the basic definition of an element, a French chemist Antoine Laurent Lavoisier laid down the basic definition for testing whether a substance fitted its definition. Antoine Lavoisier, The Father of Modern Chemistry Innovative and scientific approaches paved the way for the rapid development of chemistry. In 1770, Antoine Lavoisier gained wide recognition when he refuted the then prevalent belief that water is converted into earth by repeated distillation. By carefully weighing both the earthy residue and the distilling apparatus, he demonstrated that the solid matter came from the glass vessels and not from the water. Speculating on the nature of the traditional four elements—earth, water, air, and fire, he began to investigate the role of air in combustion. On November 1, 1772, he stated that when burned sulfur and phosphorus increased in weight because they absorbed “air”. On the other hand, the metallic lead formed when litharge was heated with charcoal weighed less than the original litharge because it had lost “air.” He gave phlogisticated air the name oxygen, or “acid producer” He explained phlogiston theory as the result of the combination of the burning substance with oxygen. This theory was later revised and now known as the theory of combustion. On June 25, 1783, he also explained that water was the product formed by the combination of hydrogen and oxygen. An English chemist named Henry Cavendish opposed this idea and later was able to produce quantities of hydrogen, called “inflammable air,” by decomposing water into its constituent gases. Because of Lavoisier’s findings, chemists tasted the first sound understanding of the nature of chemical reactions. His experiments paved the way for the flourishing of modern chemistry. Thus, he became known as the Father of modern chemistry. Soon after, chemists like Joseph Priestly, John Dalton, Niels Bohr, Ernest Rutherford, the Curies and other scientists made new advancements in chemistry. These advancements led to many distinct branches of chemistry. Branches of Chemistry 1. Organic Chemistry is the study of the compounds of carbon. This branch of chemistry is important to the petrochemical, pharmaceutical and textile industries. All living organisms have traces of carbon. 2. Inorganic Chemistry is the study of chemical elements and their compounds except carbon. 3. Other branches: a. Physical Chemistry deals with the relations between the physical properties of substances and their chemical formations along with their changes. b. Biochemistry is a science that fused biology and chemistry. It is concerned with the composition and chemical reactions that occur in the formation of living species. c. Analytical Chemistry deals mostly with the composition of substances. It seeks to improve means of measuring chemical composition of natural and artificial materials. In medicine, this is the basis for clinical laboratory tests for disease diagnosis. The nutritional value of the food we eat is determined through chemical analysis. Analytical chemists analyze many household products. Importance of Chemistry Chemistry plays a very important role in different areas of life. Some people view chemistry as a very technical subject that deals with formulas and mind-boggling computations. This may be true, but if you will try to look at things around you, you will begin to appreciate its importance. The products of chemistry and technology are highly useful. For example, when you go to a beauty saloon and ask the hair stylist to straighten or curl your hair, she/he needs to use a correct solution, or else it will not come out right. Chemistry also plays a very important role in medicine, engineering, agriculture, photography and other related fields. LESSON 2: SCIENTIFIC METHOD OF SOLVING PROBLEMS 1. STATE/IDENTIFY THE PROBLEM – Identify the problem you want to solve. Break it into smaller parts. Carefully plan how to proceed in getting as much information as possible about the problem. 2. GATHERING OF DATA – Collect information or data concerning the problem through observation. 3. FORMULATE THE HYPOTHESIS – Hypothesis is an educated guess. Forming this would help you find out what the answer to your problem might be. 4. TEST THE HYPOTHESIS – Do further experiment to verify your hypothesis. 5. RECORDING AND ANALYZING DATA – interpret and evaluate the information gathered. Do calculations if needed to come up with your conclusion. 6. STATING A CONCLUSION – this answers the problem stated. If the problem is still unsolved, try a new approach or perform another experiment. Repeat the steps from the beginning until a solution may become clear. LESSON 3. SCIENTIFIC MEASUREMENT Chemistry is an experimental and a quantitative science. The development of its principles is based on carefully designed experiments carried out under controlled conditions. At the heart of any quantitative experiment in our surroundings and in laboratories is the performance of operations called measurements. Measurements are made nearly everyday, not only in the laboratory but in every establishment and even at home. This lesson will take you to the world of scientific measurements. Read this lesson and learn to appreciate its importance. METRIC – The Universal Language of Scientific Measurement Measurement is the process of comparing a known quantity like a measuring device to an unknown quantity or the things or objects to be measured. It is the process of determining how many times a certain quantity is contained in a standard measuring device. The scientific system of measurement is called the metric system. The metric system is often referred to as the International System of Units, or SI. Scientists throughout the world use the metric system of measurement. The two subdivisions of the metric system are the mks (meter-kilogram-second) and cgs (centimeter-gram-second). It is based on units of ten. SI consists of three classes of units that form coherent set base units, derived units and supplementary units. There are seven basic or fundamental units considered in the SI. Fundamental Quantities are quantities that can be measured directly using measuring devices. Basic Types of Physical Quantities 1. Mass (m) is a basic property of matter. It is the measure of the amount of matter it contains. The standard unit of mass is the kilogram, kg. One kilogram (kg) is the mass of 1 liter (L) of water at 4C and a pressure of 1 atmosphere (atm). The mass of an object remains the same even if the position of the object is changed with reference to the earth’s center. It is measured using the triple beam balance or the equal arm balance. 2. Length (l) is a distance between two distinct points. It is measured by using a metric ruler. Width (w) is also a length, and height (h), is the vertical distance. The basic unit is the meter (m). 3. Time (t) is the regular interval between two successive points. The standard unit of time is the second. The second was originally defined in terms of the motion of the earth, but it was revised and instead compared to vibrations of cesium atoms. 4. Temperature (T) is the measure of the hotness or coldness of an object. It is technically defined as the measure of the average kinetic energy of a body. Kelvin (K) is used as the basic unit. 5. Electric current (I) is the measure of the flow of electrons or charges. An ammeter is used to measure current expressed as Ampere (A). 6. Luminous intensity (E) is the amount of illumination received by an object. The unit of measure used to describe this is candela (cd). 7. Amount of substance (n) is the number of moles. The basic unit is the mole or mol. The different units of measurements are used in our day-to-day activities. When you go the gas station to fill up your gas tank, the unit of measurement used is liter. In the sari-sari store or supermarket, the units used for mass are grams and kilograms. For volume, milliliters or liters are used. On road markers, the distances are measured in kilometers. The most common measurements you will be using in the laboratory are those of length, mass, volume and temperature. The Common Metric Units Length Mass 1 meter, m = 100 centimeters, cm 1 meter, m = 1000 millimeters, mm 1 meter, m = 1000 000 micrometers, m 1000 meters, m = 1 kilometer, km 1 kilogram, kg = 1 000 grams, g 1 gram, g = 1000 milligrams, mg 1000 kilograms, kg = 1 metric ton Volume Temperature 1 Liter, L = 1000 milliliters, mL 1 Liter, L = 1000 cubic centimeter, cc C = 5/9(F – 32) or C = (F – 32)/ 1.8 F = 9/5(C) +32 or F = 1.8(C) +32 Kelvin, K = C + 273 The Table of Prefixes Prefix Symbol Powers of Ten Example Deci d 0.1 =10-1 decimeter, dm Centi c 0.01 =10-2 centimeter, cm Milli m 0.001 =10-3 milligram, mg Micro 0.000001 =10-6 microgram, g Nano n 0.000000001 =10-9 nanometer, nm Deka da 101 = 10 dekagram, dag Hecto h 102 = 100 hectometer, hm Kilo k 103 = 1 000 kilogram, kg Mega M 106 = 1 000 000 Megagram, Mg Giga G 109 = 1 000 000 000 Gigameter, Gm Metric – English Equivalents Metric English 1 Liter, L 1.06 quartz, qt. 250 milliliter, mL 1 cup, c 1 kilogram, kg 2.2 pounds, lb. 28.3 grams, g 1 ounce, oz. 3.79 Liters, L 1 gallon, gal. Study the examples. 4. Convert 75 millimeters (mm) to its corresponding length in a. meters b. centimeters c. kilometers Solution: 5. Change 430 milligrams to grams From the Table of Prefixes , milli = 10-3 Change the powers of ten to a prefix. 430 x 10-3 grams By the use of scientific notation, it would be 4.30 x 102 x 10-3 The final answer is 4.30 x 10-1 6. 5 gallons of mineral is equivalent to how many liters? 7. 2 x 109 bytes is equal to 2 Gigabytes or 20 Gb 8. The normal body temperature is 37C. What is its equivalent in F and K? Formula: Solution: or 98F is equal to ____C 9. The density of water in the cgs is 1 g/cm3. What is its density in mks? SCIENTIFIC NOTATION is a compact, simple and easy way of writing down very small and very large numbers using powers of ten. The exponent tells the number of times the decimal point is moved from its original place to the right or from the original place to the left. The exponent is NEGATIVE if the decimal point is moved from left to right and POSITIVE if it is moved from right to left. Example: 1. 4 000 000 = 4.0 x 106 2. 532 000 000 = 5.32 x 108 3. 0.000000045 = 4.5 x 10-8 4. 0.0032 = 3.2 x 10-3 10. `To add and subtract numbers expressed in powers of ten, simply copy the common exponent and proceed as in addition or subtraction. (If the exponents are not the same, make them the same first before adding or subtracting) (First make the exponent the same, then add the numbers and copy the common exponent.) 11. To multiply numbers expressed in powers of ten, add the exponents. If the exponents are of different signs, meaning, one is positive and the other one is negative, add them algebraically by subtracting the smaller number from the larger number and copying the sign of the larger number. Final answer should be expressed in standard form. M.N x 10n, where M is the only digit before the decimal point, N is/are the number(s) after the decimal point, and n is the exponent. 12. To divide numbers expressed in powers of ten, subtract the exponents. If the exponents are of different signs, meaning, one is positive and the other one is negative, change the sign of the number to be subtracted and then proceed as in addition. Parallax - is the apparent shift in position of an object as it is viewed or observed at different angles. Accuracy and Precision Accuracy is a degree of agreement between a measured value and the true value. Precision is the degree of the instrument’s exactness. Significant figures – the number of digits or figures that best represents the value of a measurement. Rules in Determining the Number of Significant Figures: • All non-zero digits are significant. (1, 2, 3, 4, 5, 6, 7, 8, 9) • All zeros in between two non-zero digits are significant. 2804 has four (4) significant figures. • All zeros to the right of a decimal point but to the left of a non-zero digit are NOT significant. For example, 0.0003068 has four (4) significant figures • All zeros to the right of non-zero digit without an expressed decimal point following it are NOT significant. For example, 406,000 has three (3) significant figures, but 406,000. has six (6) significant figures because of the indicated decimal point. Graph - is a tool or mechanism to show the relationship between two variables. The two kinds of variables are the dependent variables plotted on the Y-axis or the ordinate and the independent variables plotted on the X-axis or the abscissa. LESSON 4. IDENTIFYING LABORATORY APPARATUS AND ITS USES When you think of chemists at work, you probably imagine them in a modern laboratory with test tubes, other delicate instruments, apparatus, and bottles of strange substances. You’re right! In the laboratory, you can find different laboratory apparatus. The Science laboratory is a place of adventure and discovery. Some of the most exciting events in scientific history have happened in the laboratory. The discovery of the atoms, the production of plastics for clothing, the analysis of chemicals of substances, and other discoveries were first made by chemists in a laboratory. But all these things could never have happened if there were no equipment and devices. Different laboratory apparatus served their purposes. Here are some of the laboratory equipment and their uses. Study the different apparatus grouped in each box. They are grouped according to their uses. Group I: Some apparatus used for STORING LIQUIDS Beaker Reagent bottles Florence Flask a deep wide mouthed, thin-walled, cylindrical vessel with a pouring lip used to measure large quantities of liquid; can also be used to store or contain liquid mixtures a vessel used to contain chemicals that are mixed or added with other substances to bring about chemical reactions to form new substances or compounds. a round, flat-bottomed, long necked vessel used to measure large quantities of liquid and to hold boiling liquids Group I: Some apparatus used for STORING LIQUIDS Erlenmeyer Flask Volumetric Flask Test Tubes in a Rack a cone-shaped vessel with a narrow flat bottom used to measure volume of liquid; also serves as receiver and stores liquid that is to be kept for further analysis a flat-bottom vessel with long neck container used to store liquids or solutions for observation; can also be used to measure volume of volatile liquids small, glass-tube shaped containers that are closed and round at the bottom with open end used to mix, heat and store small amounts of liquids and substances. Group II: Some apparatus used for MEASURING VOLUME Graduated Cylinder Pipette & Burette Medicine Dropper a narrow cylindrical vessel used to measure the volume of liquids and the volume of irregular solids by water displacement Pipette - used to transfer small amount of liquid of known volume to another container Burette - a glass tube with measurements marked on the side and a stopcock at the bottom, used to accurately measure the volume of liquid before releasing it in another container. a small glass or plastic tube with rubber bulb at one end that is used to suck up liquid and release it one drop at a time Group III: Apparatus used when HEATING SUBSTANCES Wire Gauze Iron Ring Iron Clamp used to protect the glassware during the heating process. used as base to hold the wire gauze and any other container to be heated used to hold the test tube, distilling flask, and other apparatus to be heated Iron Stand Bunsen Burner Clay Triangle supports the iron ring and iron clamp during heating, distillation and other extraction purposes A burner that produces hot flame by mixing flammable gas under pressure through controlled quantities of air. Supports the crucible on an iron ring when heating Crucible Tong Crucible and cover Evaporating Dish a tool used to hold hot materials or apparatus a heat resistant container with cover in which ores or materials are melted a shallow heat resistant porcelain dish in which a solution is heated and allowed to evaporate leaving a residue on its plate Group IV: OTHER LABORATORY APPARATUS Watch Glass Test Tube Brush Test Tube Holder A rounded-bottom circular plate where chemical reactions are being observed Used to clean small-mouthed containers like test-tubes Holds the test tube while heating or during an experiment Spatula Funnel Mortar and Pestle a shallow round crystal or glass dish used to hold small amounts of substances to be tested for a reaction a cone-shaped tool with large opening at the top and a small opening or tube at the bottom used to guide liquids and other substances through a small opening; used to hold filter paper during filtration Used to grind, pound and mash solid substances into powder form Double-Pan and Triple Beam Balances: Measurement of Mass The laboratory balance is an important tool in scientific investigations. You can use the balance to determine the mass of materials. Different kinds of balances are used in the laboratory. One kind of balance is the double-pan balance. Another kind is the triple-beam balance. To use the balance properly, you should learn the parts, function and location of each part of the balance you want to use. Here are the two kinds of balances. Study their parts and functions: Parts of a Double-Pan Balance and Their Functions 1. Pointer – used to determine when the mass being measured is balanced by the riders or masses of the balance 2. Scale – series of marks along which the pointer moves. 3. Zero point – center line of the scale to which the pointer moves when the mass being measured is balanced by the riders or masses of the balance 4. Adjustment knob – knob used to set the balance at the zero point when the riders are all on zero and no masses are on either pan 5. Left pan – platform on which an object whose mass is to be determined is placed 6. Right pan – platform on which standard masses are placed. 7. Beams – horizontal strips of metals on which marks or graduations appear that indicate grams or parts of grams 8. Riders – devices that are moved along the beams and used to balance the object being measured to determine its mass 9. Stand – support for the balance. How to Use the Double-Pan or the Platform Balance As the name implies, the double beam or platform balance has two beams. The beams are calibrated or marked in grams. The upper beam is divided into ten major units of 1 gram each. Each of these units is further divided into units of 1/10 of a gram. The lower beam is equal to 10 grams. The lower beam can be used to find the masses of the objects up to 200 grams. Each beam has a rider that is moved to the right along the beam. The rider indicates the number of grams needed to balance the object in the left pan. Before using the balance, be sure that the pans are empty and both riders are set to zero. If your pointer does not read zero, slowly turn the adjustment knob so that the pointer does read zero. The following procedure can be used to find the mass of an object using the double-pan balance: 10. Place the object whose mass is to be determined on the left pan. 11. Place the standard masses on the right pan. 12. Be sure that the pointer indicator should be at zero, meaning, the left pan and the right pans are balanced. 13. Count the number of standard masses. Its equivalent is equal to the mass of the objects weighed. The triple beam balance is a single-pan balance with three beams calibrated in grams. The front beam or 100-gram beam is divided into ten units of ten grams each. The middle or 500-gram beam is divided into five units of 100 grams each. The back beam or 10-gram beam is divided into 10 major units of 1 gram each. The following steps can used to find the mass of an object using a triple beam balance: 1. Place the object to be weighed on the pan. 2. Move the rider on the middle beam notch by notch until the horizontal pointer drops below zero. Move the rider back to one notch. 3. Move the rider on the front beam notch by notch until the pointer again drops below zero. Move the rider back to one notch. 4. Slowly slide the rider along the back beam until the pointer stops at the zero point. 5. The mass of the object is equal to the sum of the readings on the three beams. LESSON 5. LABORATORY SAFETY/PRECAUTIONS Science is a hands-on laboratory class. You will be doing many laboratory activities that require the use of different apparatus and hazardous chemicals. Safety in the science classroom is the number one priority for students and teachers. To ensure a safe science classroom, a list of rules has been developed. These rules must be followed at all times. The science laboratory is a safe place to work in if you are careful. Following are some safety precautions to help you protect yourself from injury in the laboratory while doing the experiment. Read and understand them to insure your safety before, during, and after doing an experiment. A. Inside the Laboratory 1. Do not eat food, drink beverages, or chew gum in the laboratory. Do not use laboratory glassware as containers for food or beverages. 2. Safety goggles and aprons must be worn whenever you work in the lab. Gloves should be worn whenever you use chemicals that cause skin irritations or when you need to handle hot equipment. 3. Observe good housekeeping practices. Work areas should be kept clean and tidy at all times. 4. Know the locations and operating procedures of all safety equipment including the first aid kit, eyewash station, safety shower, spill kit, fire extinguisher, and fire blanket. Know where the fire alarm and the exits are located. 5. Be alert and proceed with caution at all times in the laboratory. Notify the instructor immediately of any unsafe conditions you observe. 6. Dispose all chemical waste properly. Never mix chemicals in sink drains. Sinks are to be used only for water and those solutions designated by the instructor. Solid chemicals, metals, matches, filter paper, and all other insoluble materials are to be disposed of in the proper waste containers. 7. Labels and equipment instructions must be read carefully before use. 8. Keep hands away from your face, eyes, mouth, and body while using chemicals. Wash your hands with soap and water after performing all experiments. Clean (with detergent powder), rinse, and dry all work surfaces and equipment at the end of the experiment. 9. If you spill acid or any other corrosive chemical on you skin or clothes, immediately wash the area with large amounts of water (remember that small amounts of water may be worse than no water at all). After this, get the teacher’s attention. The spill kit will be used for spills on floor or counter-top. 10. After doing an experiment check if: a) the main gas outlet valve is shut off b) the water is turned off c) the desk top, floor area, and sink are clean d) all equipment are cool, clean, and arranged properly. B. Clothing 11. Wear goggles or eye protector if necessary. 13. Dress properly during a laboratory activity. Long hair, dangling jewelry, and loose or baggy clothing are a hazard in the laboratory. Wear an apron. Shoes must completely cover the foot. C. Accidents and Injuries 1. Report any accident or any untoward incident to your teacher. 2. If a chemical should splash in your eye(s), immediately flush with running water from the eyewash station for at least 20 minutes. Notify your teacher immediately. D. Handling Chemicals 1. All chemicals in the laboratory are to be considered dangerous. Do not touch, taste, or smell any chemical unless specifically instructed to do so. The proper technique for smelling chemical fumes is to gently fan the air above the chemical toward your face. 2. Check the label on reagent bottles twice before removing any of the contents. Take only as much chemical as you need. Smaller amounts often work better than larger amounts. Label all containers and massing papers holding dry chemicals. 3. Never return unused chemicals to their original containers. 4. Acids must be handled with extreme care. ALWAYS ADD ACID SLOWLY TO WATER, with slow stirring and swirling, being careful of the heat produced, particularly with sulfuric acid. 5. Handle flammable hazardous liquids over a pan to contain spills. Never dispense flammable liquids anywhere near an open flame or source of heat. E. Handling Glassware and Equipment 1. Inserting and removing glass tubing from rubber stoppers can be dangerous. Always lubricate glassware (tubing, thistle tubes, thermometers, etc.) before attempting to insert it in a stopper. Always protect your hands with towels or cotton gloves when inserting glass tubing into, or removing it from, a rubber stopper. If a piece of glassware becomes "frozen" in a stopper, take it to your instructor for removal. 2. hen removing an electrical plug from its socket, grasp the plug, not the electrical cord. Hands must be completely dry before touching an electrical switch, plug, or outlet. 3. Examine glassware before each use. Never use chipped or cracked glassware. Never use dirty glassware. Do not immerse hot glassware in cold water; it may shatter. 4. Report damaged electrical equipment immediately. Look for things such as frayed cords, exposed wires, and loose connections. Do not use damaged electrical equipment. F. Heating Substances 1. SHOULD THE FLAME OF THE BUNSEN BURNER GO OUT, IMMEDIATELY TURN OFF THE GAS AT THE GAS OUTLET VALVE. If you wish to turn off the burner, do so by turning off the gas at the gas outlet valve first, then close the needle valve and barrel. Never reach over an exposed flame. Light gas burners only as instructed by the teacher. 2. Never leave a lit burner unattended. Never leave anything that is being heated or is visibly reacting unattended. Always turn the burner or hot plate off when not in use. 3. Do not point the open end of a test tube being heated at yourself or anyone else. 4. Heated metals, glass, and ceramics remain very hot for a long time. They should be set aside to cool and then picked up with caution. Use crucible tongs or heat-protective gloves if necessary. Determine if an object is hot by bringing the back of your hand close to it prior to grasping it.
Posted on: Wed, 31 Jul 2013 10:51:36 +0000

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