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# BIOL Exam I - Ex. 1

### Laboratory Equipment and Procedures

science the human effort to understand the history of the natural world and how the natural world works, based on physical evidence obtained through observation and/or experimentation
What are the three important properties of the natural world? - patterns - order - regularity
What is the process of science? - generate a hypothesis - design an experiment - collect data - interpret data - then repeat
How can we state the results of observations (4)? - qualitative (verbal) - quantitative (tables) - graphical (graphs) - mathematical (formulas)
control group - not exposed to the independent variable - the dependent variable in the absence of the treatment is also recorded
experimental group - exposed to the independent variable being tested - the dependent variable is observed and recorded
independent variable - a variable that stands alone and isn't changed by the other variables you are trying to measure - ex: someone's age (what somebody eats or how much TV they watch won't change their age)
dependent variable - something that depends on other variables - ex: a test score (could change depending on how much they studied, how much sleep, etc.)
The ___ variable causes a change in the ___ variable. - independent - dependent
positive control group - control group where the conditions guarantee a positive result (a response SHOULD occur) - used to show the experiment is working as planned
negative control group - control group where conditions produce a negative outcome (a response should NOT occur) - used to help identify outside influences which may be present that were not accounted for, such as contaminants
Using the formula weight of Tris (FW = 121.1), how much (to the nearest 0.01 g) is needed to prepare 50 mL of a 0.50 M solution? 3.03 g
What is the definition of pH? Negative log of the H+ concentration of a solution
Considering that micropipetters are most accurate when delivering volumes of 50-100% of their total capacity, which micropipetter(s) would you choose to MOST ACCURATELY dispense a volume of 125µL? P200
Where do you place used glass 10-mL pipets? The pipet wash container located at the back of the room
What is the proper character to indicate the start of a formula in Microsoft Excel? =
List the steps you would take if you were to break a beaker with a pH 9 solution. - report break to lab instructor - use chemical spill kit to clean - neutralize base - add absorbent to spill - dispose of in correct container
A graduated cylinder, Erlenmeyer flask, and beaker were used to measure a 60-mL volume. Which of these devices seems to be the least accurate for measuring a 60-mL volume? The most? - E. flask (followed by beaker) - graduated cylinder
What is percent error of mean? How do you calculate it? - the difference between approximate and exact values, as a percentage of the exact value - calculated avg. volume - actual volume, divided by the actual volume, then timed by 100%
What is a buffer? What does it mean when a solution is pH buffered? - substance that minimizes changes in the [H+] and [OH-] ions - it can resist changes in pH
How do you make a dilution? - obtain a stock solution of known concentration - decide on volume and concentration of diluted solution wanted - calculate volume of stock solution needed (using C1 * V1 = C2 * V2)
null hypothesis an assumption or proposition where an observed difference between two samples of a statistical population is purely accidental and not due to systematic causes
What is the H+ concentration of a solution with a pH of 9? ...a pH of 7? Of these two solutions, which of these solutions is more acidic? What is the difference in acidity between the two solutions? - pH = -log10[H+] - pH of 9 -> 10^-9 M - pH of 7 -> 10^-7 M - pH 7 more acidic because there are more H+ in the solution - pH 7 is 100 times more acidic than pH 9 (10*10)
What is a ‘Tris’ solution? Why is it extensively used in cellular and molecular biology laboratories? - one that contains Tris(hydroxymethyl)aminomethane, an organic compound - when the solution’s pH is between 7-9, it is called a “Tris buffer” - it is affordable, a good buffer, and not very reactive
Explain how the Bicarbonate Buffer System helps to maintain blood pH. - it regulates the pH in human blood via chemical equilibrium (the reaction constantly shifts) - when blood gets acidic, bicarbonate ions remove [H+] ions to form carbonic acid; when blood gets alkaline, carbonic acid dissociates
wet laboratory a room equipped with lots of running water and drains, high benches, floors that are easily mopped, surfaces that are relatively inert to chemical agents, and cabinets for storing glassware and chemical substances
fume hood - a ventilated work area - effectively carries away noxious fumes and fine powders - protects against exposure to dangerous chemical agents
liquid solution contains a liquid (usually water or ethanol) with one or more substances (such as sugar or salt) dissolved into it
solvent the liquid which constitutes most of the molecules of a solution
solute the dissolved substances within a solution
aqueous solution a solution with water as the solvent
How do you make a solution? dissolve a predetermined amount of solid material in water
What is the molar (M) unit? What does it equal? - the unit of molecular concentration most commonly used - one molar concentration equals one mole of dissolved substance per liter of solution (M = mol/L)
mole 6.02x10^23 units (molecules, atoms, ions) of a substance
A 1.0 M solution of sucrose is equivalent to ___. 6.02x10^23 molecules of sucrose per liter of solution
Sucrose (C12H22O11) has a molecular weight of 342.3 grams, so 342.3 grams of sucrose contains ___ mole(s) of sucrose molecules. 1
How would you make one liter of a 1 M aqueous solution of sucrose (FW=342.3 g)? - add some dH2O to a container - stir in 342.3 grans of sucrose until it dissolves - add a sufficient volume of water to make 1 L of total volume (after all of the sucrose is dissolved and homogeneously mixed)
What weight of sucrose (FW=342.3 g) would have to be dissolved into water to make 150 mL of a 0.50 M solution? 25.7 g sucrose
acid donates a hydrogen ion (proton) to solution and lowers the pH
base accepts a proton (or donates a hydroxide ion, OH-) to solution and increases the pH
How much CaCl2 would you need to make 200 mL of a 0.1 M stock solution? 2.94 g
What is the general equation for dilution? "concentration times volume of the stock solution equals concentration times volume of the desired final solution" (C1 * V1 = C2 * V2)
Created by: jessica.gvc