Lab 1 Measurement

Lab 1: Measurement Post-Lab Questions 1. (a) Which tool was the easiest to utilize for measuring LENGTH? WHY? (Hint: These are opinion questions. Your answers are based on personal preference.) (b) How precise is the tool you chose? Explain. (Hint: You need to cite all relevant data to justify your answer. Use standard deviation precents from Table 1.2.) a. The measuring tape was the easiest to utilize for measuring length, because you can easily lay the tape on to the table and has numbers to read for measurement. b. The measuring tape is the most precise tool compared to the other two tools. This can be proven because the measuring tape’s percent standard deviation is 0.3% while the sticks was 6.3% and the hand was 26.1%. 2. (a) Which tool led to the greatest variability in measurement of VOLUME? Explain. (Hint: You need to cite all relevant data to justify your answer. Use range from Table 1.4. Large range means greater variability). (b) Speculate why this tool might have yielded the greatest variability compared with the other tools used. a. The graduated cylinder led to the greatest variability in measurement of volume. Since the percent error was 12.2% compared to the 6.6% error for the transfer pipette and the O% for the micropipette. b. This tool might have yielded the greatest variability compared with the other tools used due to the use of both the transfer pipette and the graduated cylinder to measure the volume as there can be user error within one or both tools. Compared to the single use of the micropipette or the transfer pipette when they calculated volume. 3. (a) Which tool provided the most accurate measurement for VOLUME? Explain. (Hint: Cite data from your percent error calculation.) (b) What was the true or theoretical value we used for the volume activity? (Remember accuracy is how close the measurement is to the true value.) a. The tool that provided the most accurate measurement for volume was the micropipette. This can be concluded through the comparison of the percent error of the 3 tools which is 0% for the micropipette, 6.6% for the graduated cylinder, and 12.2% for the transfer pipette. b. The theoretical value that we used for the volume activity was 5.00grams. 4. Metric practice: Read the tables below and THINK! Refer to these tables when answering 4a-c. Prefix Kilo (K) centi (c) milli (m) micro (u or mc)** nano (n) Relation to base unit of gram/liter/meter 1000 (of base unit) 0.01 (1/100 of base unit) 0.001 (1/1000 of base unit) 0.000001 (1/millionth of base unit) 0.000000001 (1/billionth of base unit) **In medicine, the abbreviation "mc" is used but in biology we use "u" for micro. [Technically the symbol for micro in biology is the lower-case Greek letter 'mu' which is our letter 'u' with a tail on it. You will see micro abbreviated both ways: 'u' with a tail or 'u' without a tail.] Examples: Answers: 56 Kg = _?_ g 56 Kg = 56,000 g (Kilo is 1000 of base unit; multiple by 1000) 215 ml = 0.215 l (milli is 1/1000 of base unit; divide by 1000) 47.8 ug = 0.0478 mg (micro is smaller than milli by factor of 1000; divide by 1000) 47.8 ug = 47800 ng (micro is larger than nano by factor of 1000; multiply by 1000) 5.4 cm = 54 mm (centi is larger than milli by factor of 10; multiple by 10) 215 ml = _?_ l 47.8 ug = _?_mg 47.8 ug = _?_ ng 5.4 cm = _?_ mm (a) An average cheek (epithelial) cell is about 50 micrometers in diameter. Convert this to millimeters: 50um = 0.05 mm (b) Red blood cells are the smallest cells in our body averaging about 8 micrometers in diameter. Convert this to nanometers: 8 um = 8000 nm (c) The egg is the largest human cell at 0.1mm in diameter. Convert this to micrometers: 0.1 mm = 100 um 5. Micropipette practice: a) You are told to pipette 8 ul. What should the numbers in the window of the P10 read? Write the numbers from left (top) to right (bottom). b) You are told to pipette 50 ul. Which micropipette should you use (P1000 or P100 or P10) and what should the numbers in the window read? Write the numbers from left (top) to right (bottom). c) How many microliters (ul) are in one milliliter (ml)? You are told to pipette 0.5 milliliter (ml). Which micropipette do you use and what should the numbers in the window read? Write the numbers from left (top) to right (bottom). [HINT: Convert 0.5 ml to ul first.] a. Told To Skip b. The micropipette I should use is the P100 since the P100 is between 10100 where 50 is between these numbers. The numbers in the window would read 0, 5, 0. c. There are 1000 microliters in 1 milliliter. Since 0.5 ml produces 500 ul you should use the P1000 micropipette since it varies from 100-1000, and the window should read 0,5,0. Laboratory 2: General Principles of Chemistry Pre-Lab Questions 1. What is the difference between an ionic and covalent bond? [Do NOT obtain your answer from the internet! Use your lab book or textbook!] The difference between an ionic and covalent bond is that an ionic bond transfers electrons from one atom to another while a covalent bond shares electrons between atoms. 2. Define hydrophilic and give 2 examples of hydrophilic molecules from lecture class or the lab book. (Do NOT use the internet! Use your lab book or textbook!) Hydrophilic describes molecules that contain ionic and/or polar covalent bonds and will dissolve in water. 2 examples of hydrophilic molecules are bleach and ammonia. 3. Define hydrophobic and give 2 examples of hydrophobic molecules from lecture class or the lab book. (Do NOT use the internet! Use your lab book or textbook!) Hydrophobic describes molecules that do not have partial charges, and thus not attracted to water molecules. 2 examples of hydrophobic molecules are oil and hydrocarbons. 4. Why does gel electrophoresis NOT WORK to separate molecules that are neutral— that have no charge? (THINK!) Gel electrophoresis does not work to separate molecules that are neutral in charge because for the molecules to move through the agarose pores involved in gel electrophoresis it requires the application of an electrical field which neutrally charged particles cannot because they have no electric charge. 5. Why do small molecules move faster than large molecules through the agarose gel? (THINK!) Small molecules move faster than large molecules through the agarose gel because the gel matrix contains pores so, the smaller the molecule the easier it is to move through the pores and thus run through the agarose gel.