Bio211 Lab Midterm Review

Osmosis is a passive type of transport

true

During the Biomolecules lab, you will use test tubes to set up chemical reactions. It is very common for students to inadvertently drop the tubes. In a laboratory setting, where does the broken glass go?

'Sharps' waste

Osmosis depends on a concentration gradient. When this gradient is present, molecules go from the most concentrated to the least concentrated medium. This means that, when osmosis occurs, the salts from a hypertonic solution travel, through a membrane, to a hypotonic solution.

false

Osmosis utilizes the cell's ATP

false

Reducing sugars are small molecules (monosaccharides, disaccharides). Therefore, all small sugar molecules are reducing.

false

If you wished to do a statistical test comparing the respiration rates of fish and elodea, you would have more replicates, then compare the averages of respiration rates by

t-test

When you are titrating a basic solution (the analyte), the following event indicates that you should stop adding the acidic solution (the titrant):

the analyte changes color

If a cell vacuole is isotonic in relationship to the solution where it is immersed, the following happens:

the cell has no net gain of water or solute

You compared the respiration rate of fish to that of the aquarium plant elodea by titrating the water in which these organisms were allowed to do respiration. What was the purpose of the third, empty beaker?

account for the fact that the pH of water is below 8.2 (note that 8.2 is the pH at which phenolphthalein turns pink)

Solutions with pH = 5 are considered ____and have hydrogen ion concentration of ___M

acidic , 10^-5

Assume the pH of water to be around 7.0. After the fish and the elodea have respired in it, the water became ___ and ___ will be used to neutralize the solution.

acidic; base

Suppose you do not have access to a pH meter. You tested the pH of a solution using bromocresol green as your pH indicator. Bromocresol green is yellow at pHs below 3.8 and blue at pHs above 5.4 . You tested your solution with bromocresol green, and it looked yellow. You conclude that the solution is acidic, and wish to know now acidic - whether the pH is closer to 1.0 or to 3.7. If you do a titration, should you use a basic or an acidic solution as your neutralizing solution? For which end of the spectrum (pH 1 or pH 3.7) will you use more of the neutralizing solution?

basic; 1

Why is it impossible to observed osmosis in an animal cell, using solutions in the following order: 0% NaCl, 1% NaCl, and 5% NaCl

because at 0% NaCl, the cell intakes so much water, that it explodes, preventing you from observing osmosis at the other salt concentrations

Why should you measure the volume of the different organisms when you are trying to compare their respiration rates?

because by dividing by their volumes, you eliminate the error of comparing, for example, the respiration rate of a huge plant against the rate of a tiny fish.When you divide the respiration rates by the organisms' volumes, you are normalizing the data (making the comparison fair)

Why was it necessary to keep the elodea in the dark for this respiration experiment?

because in the light, the plant would do photosynthesis, which utilizes CO2, therefore underestimate its respiration rate

Data from multiple students will be combined for statistical analysis. Why can't you compare the measurements you made (diffusions of a large and a small molecules) to make conclusions about the influence of molecule size on diffusion rates?

because you need replicates to exclude chance from the outcome you observed

You performed the experiment in which you breathed into one erlenmeyer flask with phenol red solution, and did not breath into the second flask. Why were you instructed to NOT exhale in the second one?

because you needed to keep one solution undisturbed, so that you had something against which to compare the solution you disturbed

Consider two molecules with different sizes, small and large. Now consider a sieve whose pores are three times larger than the size of the large molecule. The diffusion of these molecules through the sieve will certainly occur at different rates.

false

Copy of If the calculated p-value was higher than the critical p-value, the experiment failed.

false

Even before you set up an experiment, you already know that the following hypothesis is true: the smaller the molecule, the more quickly it diffuses.

false

For diffusion to occur, the cell must utilize ATP

false

Glycolysis only occurs in the presence of oxygen

false

If the calculated p-value is higher than a established threshold (critical p-value), then this is said to be statistically significant

false

If the p-value calculated for an F-test is large, then the p-value for a t-test will also be large.

false

If the p-value calculated for an F-test is large, then the p-value for a t-test will be small.

false

If the p-value calculated for an F-test is small, then the p-value for a t-test will also be small

false

If the p-value calculated for an F-test is small, then the p-value for a t-test will be large.

false

If you are using a microscope that has only one 10x ocular lens, and are using a 40x objective lens, then the total magnification is 400x. If, however, you are using a microscope that has one 10x ocular lens for each eye, then while using the 40x objective, the total magnification will be 4,000x

false

If you are using a microscope that has only one 10x ocular lens, and are using a 40x objective lens, then the total magnification is 400x. If, however, you are using a microscope that has one 10x ocular lens for each eye, then while using the 40x objective, the total magnification will be 4,000x.

false

If you wish to determine whether or not the molecule size played a role in diffusion you can do a t-test comparing the diffusion of the small molecule at 20C, against the diffusion of the large molecule at 56C.

false

If your data agree with your hypothesis, then your hypothesis has been proven.

false

If, after titration, one of the solutions is a darker shade of color (in this experiment's case, pink) than the other two an error is introduced. For the pinker beaker, the respiration was underestimated

false

Lugol's iodine detects starch. Starch is a carbohydrate. Therefore, Lugol may be used to detect glucose.

false

A p-value quantifies the probability that

the data collected for two treatments are different solely due to chance

From experiment 2, you concluded that the cylinder that had the largest SURFACE AREA was

the largest plug

From experiment 2, you concluded that the cylinder that had the largest VOLUME was

the largest plug

You used titration to determine whether the fish or the elodea respires more. This was possible because

the more respiration, the more acidic the water, and the higher the volume of NaOH necessary for titration

Obligatory aerobic organisms cannot live in oxygen-deprived environments because

they need oxygen do to the citric acid cycle and the electron transport chain of cellular respiration

name of the technique we will use to compare acidities of different water samples

titration

'Diffusion' and 'diffusion rate' are not the same. 'Diffusion rate' is the amount of diffusion per amount of time.

true

A burette looks like a long pipette, with a valve on the bottom. It is generally used for titration.

true

As you increase the magnification your sample, each ocular space measures fewer and fewer units.

true

Benedict's test not only detects reducing carbohydrates as a yes/no answer, but also how much reducing sugar is present in the solution.

true

By taking data at several time intervals, you were able to see if the amount of diffusion per time remained the same or if it changed over time.

true

Colors are given by the wavelengths of light that are reflected by an object. Therefore, it is easier to see a microscopy sample that has color than one that is colorless.

true

Consider an aquatic organism: you can indirectly measure its ATP production by measuring the amount of base necessary to neutralize a solution that became acidic thanks to the CO2 released by respiration.

true

Diffusion depends on existence of a concentration gradient.

true

Even large organisms are composed by small cells. Cells need to be small because a lot of the transport of substances in and out of cells is done by diffusion.

true

Examples of molecules that go inside of the cell without using any energy: carbonic gas, oxygen, water, and glucose

true

For experiment 1, you measured the diffusion at each 30 minutes. If you were not interested in the change in diffusion rate over time, all you would need to do is to make the measurements at 90 minutes.

true

For the respiration experiment with the elodea and the fish: if you had not included the empty beaker as a control, the amount of respiration performed by the fish and by the elodea would be overestimated, since the whole volume of NaOH used for titration would be attributed to the acidity generated by respiration.

true

Glycolysis occurs both at aerobic cellular respiration and at fermentation

true

High p-values mean that most of the difference you see between averages of two different treatments are due to randomness.

true

Hypertonic is a term that compares the concentration of salts between two solutions.

true

If the critical p-value adopted is 0.10, you will more easily detect statistically significant differences than if you had adopted 0.05 as the critical p-value.

true

If you had not included in your experiment an empty beaker as a control, you would have attributed the total volume of titrant NaOH to the respiration of the fish or the plant. In reality, only part of the volume of NaOH used was to neutralize the acidity caused by respiration.

true

In Experiment One, you studied the rate of diffusion of two different-sized molecules, the phenol red molecule (C19H14O5S) and the hydronium ion (H3O+). To test if heat increases the rate of diffusion, you heat up a system and measure diffusion of a certain molecule AND do the same diffusion system, with a NOT heated up system. The not-heated-up system is your control.

true

In class, the reason we did the F-test was to figure out if, for the t-test, we should use "equal variances" or "unequal variances".

true

Isotonic means that the concentration in a medium is the same as the concentration in its surroundings.

true

Often times, ratios express more valuable information than absolute values

true

Osmosis requires a concentration gradient to occur

true

Percentages, by definition, express a ratio

true

Suppose that the calculated p-value of your statistical test was 0.04. If the critical p-value adoped was 0.05, then the difference between treatments IS statistically different. If, however, you adopted a critical p-value of 0.01, then the difference observed is NOT statistically different.

true

Suppose you are titrating three acidic solutions. If you add too much base to one of them, you can still rescue your experiment by adding more base to the other two solutions, trying to achieve the same shade of color in all of your treatments. As long as saturation has not occurred, the experiment should still work.

true

Suppose you have a data point on column "A", and a data point on column "B". Column "C" holds the result of the division of "A" by "B". If you want column "D" to hold the result of the division of "B" by "C", you can drag the formula horizontally. The spreadsheet will correctly calculate this.

true

The F-test compares variances whereas the t-test compares averages

true

The best predictor of diffusion rate is a combination of surface area and volume. Each of these variables, when utilized alone, do not make a reliable comparison.

true

The coarse focus is used to find a sample, and the fine focus is used to improve resolution

true

The diffusion rate of hydronium was measured by the change of color of the phenol-red/agar plates.

true

The intensity of light in microscopy: sometimes less is more

true

The iodine in Lugol gets trapped in the long helical structure of starch. This changes how light reaches the iodine molecule, and the solution becomes dark.

true

The lower the critical p-value, the harder it is for the data to support the hypothesis that treatments are statistically different.

true

The most reliable titration data are produced when the shades of color of all treatments are the same, as long as the solution is not saturated.

true

The structure of onion cells is more easily seen when you use a dye than when you use water for the wet mount.

true

The surface-area-to-volume ratio is the result of the division of a surface area by a volume.

true

Titration is the name of a technique that allows you to calculate the concentration of a chemical "A", provided that you know the concentration of chemical "B", that "A" and "B" react with each other, and that there is a visible end-point to the reaction.

true

Two replicates are not considered a large enough sample size for statistical analysis.

true

Typical critical p-values are 0.01 and 0.05. It is more difficult to claim significant statistical difference when the critical p-value is 0.01 than when it is 0.04.

true

When a solution has carbohydrate in it, the copper in Benedict's gets reduced.

true

When a solution has protein in it, the Biuret in the solution turns purple.

true

When a substance is "reduced" it means that its valence has decreased. One of the tests you performed makes cupric ions (Cu+2) be reduced to cuprous ions (Cu+). After donating electrons to copper, the donating substance becomes oxidized.

true

When you did the experiment of changing the color of phenol red by the products of your respiration, you used, as a control, a solution that was left undisturbed. The experimental design was not the best, because the controls do not address the formation of bubbles. A better design would have been to pump a gas, other than CO2, into the control solution.

true

When you place a sample on the microscope stage, you should place the slide AGAINST the specimen holder, so that the slide is secure, but will move when you use the X-Y control translational knobs.

true

When you test a solution for presence of proteins, you use a reagent called Biuret

true

Convert 100 mg to µg

100000

How does Biuret reagent detect protein in a solution?

Biuret detects peptide bonds

The random movement of molecules caused by their kinetic energy is called

Brownian

When an organism is obligatory aerobic, its glycolysis needs O2 to occur.

false

When you intend to DRAW a solution using a micropipette, you push the plunger until the _____ stop.

First

You will use copper-based solutions in the Biomolecules lab to detect sugars and proteins. Cupric sulfate in high amounts can be toxic. For your reference: the LD50 (the lethal dose that kills 50% of the population), tested in rats, is 300mg/kg. Copper should be discarded in...

Specific container

What happens if you push the micropipette plunger until the second stop when you are trying to DRAW solution?

The volume you draw is larger than the volume set

If the calculated p-value was higher than the critical p-value

the difference between data sets is not significant

Why do scientists use those plastic tips on the micropipettes?

To prevent contamination of chemicals. Each time a different chemical is pipetted, the tip is changed

Benedict's test is both qualitative (presence OR absence) and quantitative (how much).

True

One of the main principles of the scientific method is Replication

True

The value for the length of each ocular-reticle unit does not change as you change the magnification power.

false

Where does glycolysis occur?

cytoplasm

Biomolecules are generally polymers. What is the name of the reaction that allows formation of such polymers?

dehydration

The t-test is a statistical test that compares

differences between averages of TWO treatments

Did higher temperature promote significantly faster diffusion? You could figure this out by comparing

diffusion of the small molecule at 20C versus diffusion of the small molecule at 56C

Choose the BEST answer. When you blew into the solution, you produced CO2 and bubbles. Your control was an undisturbed flask with the same solution as the one into which you exhaled. Without any prior knowledge of the phenomenon that explains the color change of phenol red, and considering the experimental control utilized, which of the following options would be plausible?

either the formation of bubbles or the chemical reaction between CO2 and water

Suppose you had a strong suspicion of a certain outcome for your experiment. However, after performing the statistical tests, the conclusion did not follow your prediction. The careful scientist will

examine the raw data, to look for possible mistakes on data collection look at the size of the error bars--large error bars indicate that measurements were 'all over', distant from the mean. Conclusions made on data sets with large error bars are not very reliable

Consider two cylinders, a small and a large. You wish to measure the percentage of each cylinder that has had a compound diffusing into it. The larger cylinder will have a higher percentage of diffusion because it has a larger surface area than the small cylinder.

false

You incubate the aquatic plant elodea in water, let it respire, then use titration to determine its respiration rate. If you incubate a big sprig of the plant in one beaker and, in a separate beaker, you incubate only 10 leaves of the same plant, theoretically, the volume of NaOH for titration would be

greater for the treatment with the big sprig than for the 10-leaf treatment

Increasing the temperature increases diffusion because

it increases the kinetic energy of molecules, making them vibrate more vigorously, and therefore collide with each other more often and more strongly

In which phase of the cellular respiration was the CO2 you blew into the solution produced?

krebs cycle

Which of the following is ok to clean the lenses with?

lens paper

When a plant cell is immersed in a hypertonic solution, the cell will

lose water, and its vacuole will shrink

The reason why you measure the radial distance at 30-min intervals was to

measure if the diffusion rate remained constant

Which of the following microscopy images is the most appropriate, according to what you learned about what you should include in your microscopy drawings?

metal foam (The best microscope images are those where you can see a size-bar standard and the magnification used.)

Dye that stains nucleic acids:

methylene blue

Where does the Krebs cycle occur?

mitochondria

Where does the electron transport chain occur?

mitochondria

Osmosis

movement of liquid, due to a CONCENTRATION gradient; involves a membrane

Convection

movement of molecules through liquid or gas; commonly used for TEMPERATURE gradient

Diffusion

movement of molecules through liquid, gas, or solid, due to a CONCENTRATION gradient

You observed osmosis on a plant cell, using a isotonic, a hypotonic, and a hypertonic solutions. The responses you saw were

no change; inflation of the vacuole; shrinking of the vacuole

If you put a penny onto a slide, with the Lincoln Memorial facing up, are you likely to be able to see the memorial in detail? Why or why not?

no, because light cannot pass through the penny and reach the eyes of the person looking into the microscope's ocular lenses

Light microscopes typically have a set of three lenses, with different magnifying powers, that can be used to examine a sample. Those lenses are called

objectives

You were instructed to exhale into a solution containing phenol red. What was the goal of this experiment?

observe evidence of formation of CO2 during respiration: the CO2, when combined with water, produced carbonic acid (H2CO3), and made the water more acidic

suppose that a new drug is being tested, and its efficacy is measured by the number of degrees it lowers a patient's fever. The subjects tested are 200 people that already have fever. To half of them, you give the new drug. To the other half, you give a placebo. In the treated group (new-drug takers), the variation of fever reduction was from 1 to 3 degrees. In the control group (the placebo), the fever was reduced by 1.5 to 2.5 degrees. Even without having the raw data, you can predict that

p-value for the t-test was not significant (the averages of one group and the other were not different, suggesting that the drug does not have an effect over fever)

Bromocresol green, when in contact with acetic acid, turns yellow. Bromocresol green is

pH indicator

What is the name of the substance that changes color when the pH changes?

pH indicator

Prepare for next week's lab: one technique utilized to separate compounds in a solution is

paper chromatography

The actions below include some of the steps that you should follow when using a microscope. Match the procedure with the order you should follow.

1. Put sample on microscope slide 2. Put cover slip on 3. Place prepared slide on microscope stage, against (not under) the stage clips 4. Use lowest-power objective to locate your sample 5. Get better resolution of your sample, using the fine-focus knob

In the lab, you learned how the ocular reticle is calibrated: you compare one scale against another one. For example: for 4 ocular spaces, there were 10 stage spaces. Now, let's apply the same concept to comparing two other scales: Celsius and Fahrenheit. Water freezes at 0C = 32F, and it boils at 100C = 212F. Therefore, in one scale, there is a variation of 100 points, while in the other, the variation is 180 points. Use this information to calculate: how many degrees Fahrenheit increase if the temperature increased from 20C to 21C?

1.8

ou used phenolphthalein for the titration you performed today. Suppose you had a problem with the burette valve and could not stop the titrating basic solution right when the solution changed color. Now, as you add more base, your solution does not change the shade of pink. What is the approximate pH of the solution? (For reference: phenolphthalein is colorless at pHâ s lower than 8.2, and pink at pHâ s 8.2-12.)

11

Supposed we had 12 student groups in the class, and all 12 groups collected data on both temperatures (20C and 56C), for the small molecule. How many replicates there be for the treatment "small molecule, at room temperature'?

12

What should be the three digits that appear in the pipette setting? Pipette: P-20 Volume desired: 13µl

150

You are looking at the eyepiece reticle of a microscope. Your goal? To determine the length of a plant cell that is on your microscope slide. The length of the cell is 22 units of the eyepiece. At total magnification 100x, each unit of the eyepiece measures 10um (where um = µm = micrometers). How long is the sample, in um? (Do NOT enter units in your answer.)

220

You are looking at the eyepiece reticle of a microscope. Your goal? To determine the length of a plant cell that is on your microscope slide. The length of the cell is 10 units of the eyepiece. At total magnification 400x, each unit of the eyepiece measures 2.5um (where um = micrometers). How long is the sample, in um?

25

The LD50 of cupric sulfate is 300mg/kg. If a person weighs 100kg, how many GRAMS of cupric sulfate would that person need to ingest to reach the LD50?

30

How wide (in um) is your sample if you are using total magnification 100x and the sample is 35 ocular spaces long?

350

You used phenolphthalein for the titration you performed today. Suppose you stopped titrating exactly when the color of the solution changed. What is the approximate pH of the solution at the end-point of your titration? (For reference: phenolphthalein is colorless at pHâ s lower than 8.2, and pink at pHâ s 8.2-12.)

8.2

Factual knowledge, lab skills: Match the test to the biomolecule detected Question Selected Match A. Biuret B. Benedict's C. Lugol's iodine D. brown paper

A. Protein B. Reducing carbohydrates C. Starch D. Lipids

match the type of biomolecule with an example of its representation A. C6H12O6 B. CTNA, where C = cysteine, T = threonine, N = asparagine , A = alanine (all are amino acids) C. H2N-CH-R-COOH, where "R" is a radical D. not represented (lipid, carbohydrate, amino acid, peptide)

A. carbohydrate B. peptide C. amino acid D. not represented

Suppose that the middle-sized plugs and the small-sized plugs had the same result for your measurements of diffusion: they both diffused completely. You expected to see the medium-sized plug to have less diffusion. What is a valid explanation for your observation?

The difference between plugs was negligible, so, when you compare how much of each plug got "fed", no difference was observed. In addition, acetic acid kept being diffused while measurements were being made, which minimized the differences observed for diffusion proportions.

Choose the hypothesis that correctly addresses the question you ask in this week's experiment with the blue agar plugs in acetic acid.

The higher the ratio of surface area and volume, the faster the diffusion rate.

In the beginning of the Krebs cycle, oxaloacetate combines with acetate, and form citrate. After a bunch of reactions, the compound ends up becoming oxaloacetate again. Why does the cell bother making all these conversions?

because, in the process of making the different conversions of carbon compounds, the cell generates ATP and reducing power for posterior chemical reactions

Think of the principle that makes it possible for you to see objects magnified using the microscope. Where else do you see this principle being applied?

binoculars

How do you determine the volume of an object of irregular dimensions?

by water displacement (immerse the object into water, and measure the volume change)

Suppose that many people who take drug "x" develop a headache. Your goal is to figure out whether or not the headache is a side-effect of the drug. You compare the intensity of the pain of groups who do take the drug to that of groups who do not take it. You work for the pharmaceutical company that produces the medication, and you hope that the medication is NOT causing the headache. Therefore, you hope for a low p-value.

false

Suppose you have 25 rows of data on column "A", and 25 rows of data on column "B". If you want column "C" to hold the result of the division of "A" by "B", you need to type the formula for each row (which will make you type the same formula 25 types).

false

Suppose you have a data point on column "A", and a data point on column "B". Column "C" holds the result of the division of "A" by "B". If you want column "D" to hold the result of the division of "A" by "C", you can drag the formula horizontally. The spreadsheet will correctly calculate this.

false

The "dependent variable" is the one that typically goes on the x axis.

false

The best approach to find your sample on a slide is to start with the highest magnification, then decrease it

false

The data on the diffusion of the small molecule were significant

false

The diffusion rate of the small molecule (the hydronium released by sulfuric acid) was the same for each 30 minutes, up to 90 minutes.

false

The largest surface area promotes faster diffusion

false

The lower the p-value, the less certain you are that the treatment in question had an effect.

false

The more light, be more easily you will be able to see your sample under the microscope.

false

The radial distance for the 60-90min interval was calculated by measuring the diameter at 90min, subtracting the size of the core you used, and dividing by 2.

false

Using more NaOH to neutralize the control water (no organism breathing in it) than for the water that had fish in it does not imply any experimental error.

false

When a solution has carbohydrates in it, the copper in Benedict's gets reduced and the solution stays blue.

false

When a solution has reducing carbohydrate in it, the Benedict's solution stays blue.

false

When preparing a wet mount for a microscope, the more sample material you place on the slide, the more likely you are to see the individual structures that compose your sample.

false

When you place a sample on the microscope stage, you should place the slide UNDER the specimen holder, so that the slide does not move

false

When you write a scientific article, you should show both: the data in table and plot generated by the data from the table.

false

You ran a Biuret test and the color of the Biuret reagent for the negative control turned purple. You know that the Biuret reagent in the negative control should not have changed its color. The right thing to do is to discard the Biuret solution, because it must be bad.

false

When a plant cell is immersed in a HYPOtonic solution, the cell will

gain water, and its vacuole will become enlarged

Not all ocular reticles are created the same. Some have the spaces between tick marks greater than others. The sizes you have calculated for the reticle spaces are for the reticles we use in this lab. Suppose you go somewhere else and you use a reticle that is different from the ones we have in the lab. You need to figure out how large (in micrometers) is each space. How would you do that?

placing a "ruler" on the microscope stage (by "ruler" here, you mean a slide that has tick marks for each micrometer) and, while looking through the ocular lens, you measure the space between the ocular-reticle tick marks

You used iodine to locate amyloplasts in potato cells. What type of molecule is stained by iodine?

starch

You design the experiment with five replicates for each treatment. This means that you will have five plants that you fertilize and five plants that you do not fertilize (your control group). After applying the treatments, waiting some time for the fertilizer to have an effect over the plants, you collected data for the following height, in meters: Fertilized: average = 1.64; Control: average = 1.18. The fertilizer seems to have had an effect on the plant height. But you can only state that more confidently if you do a t-test.

true

heat increases the kinetic energy of molecules, therefore making them more agitated

true

the increase in kinetic energy makes molecules move (or vibrate) more vigorously. Therefore, the increase in kinetic energy explains why, at higher temperatures, diffusion occurs more quickly.

true

when you do titration, you need to know the concentration of the solution that is in the burette

true

you wish to test if a certain fertilizer has effect over plant flowering. You, then, test two sets plants that are all clones (genetically identical), fertilize one set, do not fertilize the other. Each set has 20 plants. You count the number of flowers after a few months, and realize that the control group (no fertilizer) varied from 1-15 flowers. The fertilizer group varied from 13-15 flowers. The F-test will probably have a significant p-value.

true

Successful microscopy is a combination of: i, appropriate slide preparation; ii, knowledge of how to use the microscope (locate sample, put it in focus, optimize light intensity). If you are having trouble using the microscope, these two controls can help you determine what the problem is:

use commercial slides, which are pre-prepared, then looking at the slide yourself; using a slide prepared by you, and asking an experienced microscoper to assist you with locating the sample

In the Biomolecules lab, you will boil water to detect sugars using a Benedict's test. Check the best method to handle the equipment.

use forceps to avoid touching the hot surface

Consider the experiment we ran in the lab. Which operation should you do to calculate the volume of NaOH necessary to quantify the respiration of fish?

volume of NaOH for fish - volume of NaOH of water control

When a solution contains starch, the color changes from ____ to _____

yellow to bluish purple

Choose the BEST answer. For the experiment with the respiration of elodea and fish: suppose you are titrating the acidic water, you have added several milliliters of base to it, and the color of the water has not changed yet. What are possible explanations to this?

you forgot to add the pH indicator to the acidic water that is being titrated the concentration of base in the burette is really low the water is very acidic