Lesson 2: Laboratory Apparatus and Techniques PDF

REVIEW: ACCURACY AND PRECISION high accuracy high accuracy low accuracy low accuracy high precision low precision high precision low precision  R Y APPA TO R A Y GUI...

REVIEW: ACCURACY AND PRECISION high accuracy high accuracy low accuracy low accuracy high precision low precision high precision low precision  R Y APPA TO R A Y GUI R AT ET BO US, CHN DE SAF A LINE L TE LESSON 2 Y D R N T S M IS A I Q HE UE C S, slides by sir dave  OBJECTIVES Identify common laboratory apparatus and explain when and how they should be used Describe and perform basic techniques in the laboratory Demonstrate and comply with safety practices in the laboratory Acquire the necessary laboratory skills and knowledge needed to safely and correctly conduct and interpret experiments and researches  COMMON CHEMISTRY LABORATORY APPARATUS LESSON 2.1  BEAKER A cylindrical glass container with a flat bottom and open top, commonly used for holding, mixing, and heating volumes of liquids or solids. ERLENMEYER FLASK A conical-shaped glass container with a flat base and narrow neck, often used for mixing, heating, or storing liquids. The shape allows for effective swirling and prevents splashes. VOLUMETRIC FLASK A precision glass container with a narrow neck and flat bottom, used for accurately preparing and measuring a specific volume of liquid solution. FLORENCE FLASK A round-bottomed glass flask with a long neck, used for uniform heating of liquids and distillation processes.  WATCH GLASS A round, shallow glass dish used to cover beakers or to evaporate small amounts of liquid, preventing splashes and contamination.  SPATULA A flat, scoop-like tool made of metal or plastic, used for transferring solid chemicals or scraping substances from surfaces.  FUNNEL A cone-shaped tool typically made of glass or plastic, used to channel liquids or fine-grained substances into containers with smaller openings.  STIRRING ROD A slender glass or plastic rod used to mix substances or aid in transferring liquids. GRADUATED CYLINDER A tall, narrow glass tube with calibrated markings used to measure and dispense specific volumes of liquids. GRADUATED PIPETTE A calibrated glass or plastic tube used to transfer precise volumes of liquid, with markings for measuring various volumes. VOLUMETRIC PIPETTE A precision pipette designed to deliver a single accurate volume measurement, often used for preparing standard solutions.  ASPIRATOR A device used to create a vacuum by drawing air or liquids through a system, often used for pipettes.  PASTEUR PIPETTE A small glass or plastic tube with a bulb at one end, used to transfer and dispense small amounts of liquids. TEST TUBE AND RACK A small cylindrical glass tube used for holding and mixing small quantities of substances, typically placed in a rack for stability  CORK A stopper made of natural or synthetic material, used to seal containers such as test tubes, and prevent leaks or contamination.  SPOT PLATE A porcelain plate with small depressions on the surface used to perform and study reactions on a small amount of chemicals  THERMOMETER An instrument for measuring temperature, often containing a bulb filled with a temperature-sensitive liquid, such as mercury, that expands or contracts with temperature changes. ACID-BASE BURETTE A calibrated glass tube with a stopcock, used for precise delivery of an acid or base solution during titration experiments. SEPARATORY FUNNEL A conical-shaped glass container with a stopcock, used for separating immiscible liquids based on differences in density.  REAGENT BOTTLES Containers for storing chemicals, usually made of glass with a stopper or cap, to protect and preserve reagents.  VIALS Small glass or plastic containers with a secure closure, used for storing and transporting small amounts of liquids or solid samples.  WASH BOTTLE A plastic bottle with a nozzle used to dispense a controlled stream of water or solvent for rinsing lab equipment or adding reagents, or diluting. OTHER EQUIPMENT IN OUR LABORATORY TRIPLE BEAM BALANCE An instrument used to measure mass. It consists of three beams, each of which is provided with a single sliding weight that has a size corresponding to the graduations of the notched scale on each beam. ANALYTICAL BALANCE A balance designed to measure small mass in the sub-milligram range. The measuring pan is inside an enclosure with doors to prevent dust and air from interfering.  pH PEN A device used to measure the acidity or basicity of a solution expressed as pH (generally 1-14)  CENTRIFUGE A device used to separate particles suspended in a liquid according to particle size and density, viscosity of the medium, and rotor speed.  FUME HOOD A local ventilation device that is designed to limit exposure to hazardous or toxic fumes, vapors, or dusts. BASIC LABORATORY TECHNIQUES LESSON 2.2 BASIC LABORATORY TECHNIQUES A. MEASUREMENT OF SAMPLES 1. Using a top-loading balance (solids) When weighing solid reagents (such as powders or pellets), use a watch glass and not a piece of paper as holder. A spatula may be used to transfer the solid to the balance. A heaping spatula-full contains 0.10 to 0.15 g of solid.  USING A TOP-LOADING BALANCE 1. Make sure balance is clean and calibrated. 3. 5. 7. 0.00 5.00 g 6. 20.00 TARE 4. 8. 2. on/off  USING A TRIPLE BEAM BALANCE beam scales: 100 g 500 g 10 g riders beams pointer zero 0 & zero adjustment mark knob  USING A TRIPLE BEAM BALANCE 1 Make sure balance is clean and calibrated. 7 Add the values of all three beams to determine the mass of the solid. 2 *do the same for the topmost rider as in #3 4 3 0 6 5 BASIC LABORATORY TECHNIQUES A. MEASUREMENT OF SAMPLES 2. Using a top-loading balance (liquids) Use a glassware or any clean container to measure the mass of a liquid on a balance. Measure the mass of the empty glassware first then subtract it from the mass of the glassware with the liquid. BASIC LABORATORY TECHNIQUES A. MEASUREMENT OF SAMPLES 3. Using a graduated cylinder (volume of solids) Fill a graduated cylinder partially with water. Take note of the volume. Submerge the solid (must be denser than the water) fully. Take note of the new volume. Subtract the final and initial volumes to get the volume of the solid. BASIC LABORATORY TECHNIQUES A. MEASUREMENT OF SAMPLES 4. Using a pasteur pipette (liquids) One standard drop of a solution is 0.05 mL; 1 mL = 20 drops. A “few drops” means 1-2 drops while “several drops” means 3-6 drops. BASIC LABORATORY TECHNIQUES A. MEASUREMENT OF SAMPLES 5. Using graduated/volumetric pipettes (liquids) a. Insert the tip of the pipette into the beaker of solution so that it is about 1/4” from the bottom. Do not press the tip against the bottom of the container. b. Hold the pipette in your dominant hand, leaving your index finger free to place over the top of the pipette. BASIC LABORATORY TECHNIQUES A. MEASUREMENT OF SAMPLES 5. Using graduated/volumetric pipettes (liquids) c. With your non-dominant hand, squeeze the aspirator then press it firmly over the top of the pipette. d. Release the pressure on the aspirator and allow the solution to flow into the pipette until it is above the volume mark. Do not allow the solution to reach the aspirator. BASIC LABORATORY TECHNIQUES A. MEASUREMENT OF SAMPLES 5. Using graduated/volumetric pipettes (liquids) e. Quickly remove the aspirator and place your index finger firmly over the top of the pipette. Slowly roll you finger to one side and allow the liquid to drain until the desired volume mark. f. Press your index finger firmly on the top of the pipette before pulling it out of the solution. BASIC LABORATORY TECHNIQUES A. MEASUREMENT OF SAMPLES 5. Using graduated/volumetric pipettes (liquids) g. To transfer the solution, place the tip of the pipet against the wall of the receiving container at an angle of 10-20 degrees. Slowly allow the liquid to drain from the pipet. Keep the flow slow so that no droplets cling to the inside of the pipette.  5 4 TWO TYPES OF 6 GRADUATED 5 PIPETTE 7 6 8 7 MOHR SEROLOGICAL DO NOT EMPTY OUT EMPTY OUT Leave liquid after the 10 mL mark. 9 8 The 10th mL is after the 9 mL mark. 10 9 THERE IS LIQUID LEFT IN THE SEROLOGICAL PIPETTE AFTER DISPENSING. DO I BLOW IT OUT WITH THE ASPIRATOR? Two rings Frosted band DON’T BLOW-OUT AFTER BLOW- DISPENSING OUT LIQUID Liquid left already For pipettes with taken into account rings or frosted bands Note: both are now serological pipettes BASIC LABORATORY TECHNIQUES A. MEASUREMENT OF SAMPLES 5. Using graduated/volumetric pipettes (liquids) When observing volumes in graduated pipettes or cylinders, read the point on the scale that coincides with the bottom of the meniscus of the liquid at eye level. Never dip the pipette directly out of the reagent bottle to avoid contamination. Transfer to a clean, dry beaker first.  4 READING THE PIPETTE OR GRADUATED CYLINDER VOLUME 5 6 7 read at eye level 8 9 Parallax Error: occurs when the scale of the pipette or cylinder is not viewed from a perpendicular position BASIC LABORATORY TECHNIQUES A. MEASUREMENT OF SAMPLES ERRORS IN MEASUREMENTS: Systematic Error: consistent, repeatable error associated with faulty equipment or a flawed experiment design. Example: incorrectly calibrated balance Random Error: has no pattern; can’t be predicted & are usually unavoidable, but can be minimized through repeated trials Example: fluctuation of power supply during use of electronic balance BASIC LABORATORY TECHNIQUES B. ADDITION OF REAGENTS 1. Using pasteur pipettes (liquids) a. When getting from reagent bottles, do not allow the tip of the pipette to come in contact with anything outside the bottle. b. Hold the dropper just above the mouth of the vessel (where you will transfer the liquid) and allow the reagent to fall. Do not let the dropper touch or rest against the inside of the vessel. BASIC LABORATORY TECHNIQUES B. ADDITION OF REAGENTS 2. Using a spatula (solids) a. In getting solid reagents, transfer out the solid from the reagent bottle to a clean dry watch glass. b. Add the reagent from the watch glass to your reaction mixture by means of a clean dry spatula. BASIC LABORATORY TECHNIQUES C. MIXING 1. Using test tubes If the solution is less than half of the test tube, it can be mixed by holding the test tube upright between the palms of your hands and rolling it sufficiently for complete mixing. BASIC LABORATORY TECHNIQUES C. MIXING 2. Using a stirring rod When using a beaker, stir using a glass rod via a combination of up and down circulatory motions. Take care not to touch the sides of the beaker, as you stir the solution. BASIC LABORATORY TECHNIQUES D. HEATING SOLUTIONS When heating solutions in test tubes, a hot water bath is recommended. A water bath can be prepared by filling up a beaker with distilled water to a level that will make the level of the liquid inside the test tube lower than the level of the liquid outside. BASIC LABORATORY TECHNIQUES E. SMELLING VAPORS Chemical substances should not be inhaled or smelled, unless otherwise instructed. If a substance or solution is to be smelled, place the container of the substance or solution a few inches away from your face. Using your other hand, waft the fumes towards you. BASIC LABORATORY TECHNIQUES F. TEST FOR ACIDITY/BASICITY Place a small piece of litmus paper on a watch glass. Dip a glass rod in the test solution and moisten the litmus paper. (color change: red to blue- basic; blue to red- acidic) If a pH paper/universal indicator will be used, compare the color developed against the scale provided. BASIC LABORATORY TECHNIQUES G. FILTRATION a. Prepare either a conical or a fluted filter paper. b. Fit the filter paper into the funnel. The edge of the filter paper must be at least ½ cm lower than the lip of the funnel. c. When filtering, guide the liquid from the source beaker with a glass rod, letting the liquid flow by the thicker side of the filter paper (for conical). 1. 2. 3. 4. Cut one flap If filter paper is square, cut into a circle first. conical filter paper Open preferred if you want to collect the solid left in the filter paper after filtering  b 1. 2. 3. 4. a c creased crease c a b Fold a to center 5. b to edge fluted filter c to center backwards unfold paper preferred if you want to collect the liquid that goes into the receiving vessel BASIC LABORATORY TECHNIQUES CALCULATING PERCENT YIELD Chemical reactions in the real world do not always go exactly as planned on paper. Besides spills and other experimental errors, there are often losses due to an incomplete reaction, undesirable side reactions, etc. Chemists need a measurement that indicates how successful a reaction has been. This is called the percent yield. BASIC LABORATORY TECHNIQUES CALCULATING PERCENT YIELD Theoretical yield is the maximum amount of product that could be formed from the given amounts of reactants (calculated stoichiometrically). Actual yield is the amount of product that is actually formed when the reaction is carried out in the laboratory. BASIC LABORATORY TECHNIQUES CALCULATING PERCENT YIELD Example: The theoretical yield of the decomposition of 1.006 g of NaHCO 3 is 0.6345 g of Na 2 CO 3. If a chemist obtained 0.434 g of Na 2 CO 3 , what is the percent yield? Answer: 68.4% Does a high percent yield always mean a successful reaction? BASIC LABORATORY TECHNIQUES CALCULATING PERCENT YIELD Predict the EFFECT of the following to the PERCENT YIELD: 1. Product spilled before weighing DECREASE 2. Insufficient drying of product INCREASE 3. Presence of chemical impurities in product INCREASE 4. Some reactants evaporate before reacting DECREASE OTHER IMPORTANT LABORATORY PRACTICES WASHING GLASSWARE a. Use tap water and a sponge with soapy water to scrub the inside of the glassware. b. Remove soapsuds with distilled water (using a wash bottle). c. If water will affect the final solution, you can rinse with the solution you're using to remove the water. d. Make sure that the glassware is dry before using again. OTHER IMPORTANT LABORATORY PRACTICES LABELLING Each container must be labeled with the identity of the chemical in it. Whenever a chemical is transferred to an unlabelled container, a new label must be created and securely attached to the container. Commonly used for labels: masking tape, price tag sticker LABORATORY SAFETY GUIDELINES LESSON 2.3  A. PREPARING FOR LABORATORY WORK 1. READ THE PROCEDURES WELL 2. PREPARE A MATERIAL SAFETY DATA SHEET (MSDS) MATERIAL SAFETY DATA SHEET (MSDS) SAMPLE When handling hazardous chemicals, MSDS must be prepared for reference inside the lab. Chemical Chemical Physical LABORATORYHazards SAFETY GUIDELINES First Aid Name Formula Properties Odor: Pungent Skin contact: can cause Skin contact: Immediately severe burns and irritation. flush skin with plenty of Color: Colorless water for at least 15 minutes Ingestion: can cause Molar Mass: severe injury to insides Ingestion: if swallowed, do 36.458 g/mol Hydrochloric NOT induce vomiting. HCl Acid Inhalation: can cause Boiling point: respiratory tract irritation Inhalation: Move to fresh air. 83 o C and shortness of breath Eye contact: Rinse or flush Freezing point: Eye contact: can cause eye exposed eye gently using -66 o C damage, even blindness water for 15-20 minutes.  LABORATORY SAFETY GUIDELINES B. PERSONAL PROTECTIVE EQUIPMENT (PPE) B. PERSONAL PROTECTIVE EQUIPMENT (PPE) NO/WRONG PPE, NO PETA!  LABORATORY SAFETY GUIDELINES C. SAFETY RULES to prevent laboratory accidents C. SAFETY RULES 1. No food, drinks, or gum inside the laboratory. 2. Never work alone. Make sure you are supervised. 3. No loitering/horseplay. Concentrate on the experiment. 4. Do not perform unauthorized experiments. 5. Read the labels. Check the formula and concentration. 6. Handle all chemicals with extreme caution. Treat all of them as potentially dangerous. 7. Never remove chemicals from the lab or stock room. 8. Be orderly and dispose wastes properly.  LABORATORY SAFETY GUIDELINES D. REPORTING TO THE TEACHER in case of accidents D. REPORTING TO THE TEACHER Immediately inform the teacher: 1. any major spills, breakages, or accidents in the laboratory; -a breakage slip must be filled out and submitted to the laboratory custodian when glassware is broken 2. all physical injuries sustained in the laboratory (such as burns and cuts) or when parts of the body get in contact with hazardous chemical -check MSDS for first aid LABORATORY SAFETY GUIDELINES E. CLEANLINESS a must E. CLEANLINESS 1. Avoid contaminating the reagents. 2. Rinse droppers and rods immediately after use. 3. Refrain from accumulating dirty glassware. Use waiting times to clean glassware. 4. Always wash or wipe off dirt from reagent bottles. 5. Clean up spills immediately even if it is only water. 6. Wash your hands thoroughly before leaving the laboratory and dry them on a clean towel.  R Y APPA TO R A Y GUI R AT ET BO US, CHN DE SAF A LINE L TE LESSON 2 Y D R N T S M IS A I Q HE UE C S, slides by sir dave