Secondary & College Biology Students' Misconceptions About

Secondary & College Biology Students' MisconcepoonsAbout Diffusion & Osmosis

ArthurLouis Odom

T he diagnosisof students'misconceptions and 2. To determine whether students differ in their the identification of reasons for those miscon- understanding of diffusion and osmosis conceptions is a prerequisiteto developing lessons cepts. that result in conceptual change. In recent years, 3. To determine whether males and females differ research on students' misconceptions has been of in their understanding of diffusion and osmosis considerable interest to science educators and cogni- concepts. tive psychologists. It is now generally agreed that 4. To determine if there is any interactionbetween Downloaded from http://online.ucpress.edu/abt/article-pdf/57/7/409/47314/4450030.pdf by guest on 30 September 2021 every student brings to science class his/her concep- class (secondary, nonmajorand major)and gen- tions of the world, and because of students' wide der with regard to understanding diffusion and variety of experiences, each concept will hold a osmosis concepts. somewhat different meaning. Further, many of the conceptions will be different from those generally accepted by the scientific community. In this article Methods & Procedures the term misconception refers to students' ideas that The Diffusion and Osmosis Diagnostic Test are different from those generally accepted by scien- (DODT)was used to detect misconceptions (Odom & tists. Barrow,in press). The diagnostic test was developed Diffusion and osmosis are widely taught in many using procedures that have been used in earlier secondary and college biology curriculums.There are researchby Treagust (1985), Peterson (1986), Haslam several reasons why we should focus on diffusion and Treagust(1987), Gorjanc-Barthel(1989), and Kio- and osmosis concepts in biology. Diffusion and os- kaew (1989). mosis are key to understanding many important life Items for the diagnostic instrument are based on processes. Diffusion is the primary method of short the two-tier, multiple-choice format. The first tier distance transport in a cell and cellular systems. An consists of a content question with two, three or four understanding of osmosis is key to understanding choices. The second tier consists of four possible water uptake by plants, water balance in aquatic reasons for the first part: three alternative reasons creatures, turgor pressure in plants, and transportin and one desired reason. The alternativereasons were living organisms. In addition, diffusion and osmosis based on misconceptions previously detected during are closely related to key concepts in physics and a multiple-choice test with free response reason and chemistry such as permeability and the particulate interview sessions. nature of matter (Friedler,Amir & Tamir 1987). The content boundaries of the final instrument were defined by a list of propositional knowledge Purpose statements (Figure 1). A specification grid (Figure2) Because of the diversity of diffusion and osmosis was constructed to determine the face validity and concepts and their importance in understanding whether the test questions matched all of the vali- science/biological systems, an evaluation of biology dated content specified by the propositional knowl- students' understanding is needed so more effective edge statements. Two major questions were ad- teaching methods can be developed. The purpose of dressed while determining face validity: this study was to determine the following among 1. Does the question assess the content as defined secondary biology students, college nonbiology ma- by the validated propositional jors and biology majors: knowledge statements? 1. To identify students' misconceptions about dif- 2. Is the question at a level of sophisticationappro- fusion and osmosis. priate for college freshman biology students? If the above criteria were not met, then the item ArthurLouls Odom is AssistantProfessor of Science Educationat was dropped. All 22 propositional knowledge state- the Universityof Missouri,5100 RockhillRd., Kansas City, MO 64110-2499. ments were matched to the items on the Diffusion and Osmosis Diagnostic Test.

DIFFUSION& OSMOSIS 409 1. All particles are in constant motion. Propositional 2. Diffusion involves the movement of particles. Item KnowledgeStatement 3. Diffusion results from the random motion and/or collisions of particles (ions or molecules). 1 2,4 4. Diffusion is the net movement of particles as a result 2 2, 4, 5, 6, 7, 12 of a concentrationgradient. 3 2,3,4,11,12 5. Concentrationis the number of particlesper unit 4 5 volume. 5 4,5,6,8 6. Concentrationgradient is a differencein concentration 6 1,2,3,8 of a substance across a space. 7 9, 10 7. Diffusion is the net movement of particles from an 8 14, 19, 21 area of high concentrationto an area of low 9 15, 16, 17, 18 concentration. 10 14, 19, 22 8. Diffusion continues until the particles become 11 13, 20 uniformly distributedin the medium in which they 12 21, 22 are dissolved. 9. Diffusion rate increases as temperatureincreases. Figure2. Spec,ificationgrid of the propositionalknowledge 10. Temperatureincreases motion and/or particle statements matched with items in the Diffusion and Osmo-

collisions. sis Diagnostic Test. Downloaded from http://online.ucpress.edu/abt/article-pdf/57/7/409/47314/4450030.pdf by guest on 30 September 2021 11. Diffusion rate increases as the concentrationgradient increases. 12. Increased concentrationincreases particle collisions. 13. Diffusion occurs in living and nonliving systems. Subjects 14. Osmosis is the diffusion of water across a The DODT was administered to 116 secondary semipermeablemembrane. 15. Tonicity refers to the relative concentrationof particles biology students, 123 nonbiology majors, and 117 on either side of a semipermeablemembrane. biology majors. The secondary students attended a 16. A hypotonic solution has fewer dissolved particles suburbanhigh school located in a large metropolitan relative to the other side of the membrane. area in the Mqidwest.Each student was enrolled in 17. A hypertonic solution has more dissolved particles either Biology I or Biology II. The grade levels ranged relative to the other side of the membrane. 18. An isotonic solution has an equal number of dissolved from 10th to 12th grade. The college nonbiology and particles on both sides of the membrane. biology majors attended a large Midwestern univer- 19. Osmosis is the net movement of water (solvent) sity. The nonbiology majorswere enrolled in a course across a semipermeablemembrane from a hypotonic specifically designed to meet the general education solution to a hypertonic solution. science requirements for nonscience majors. The bi- 20. Osmosis occurs in living and nonliving systems. 21. A semipermeablemembrane is a membrane that ology majors were enrolled in a first year general selectively allows the movement of some substances biology course for science/biology majors. Prior to across the membrane while blocking the movement of administrationof the test, each type of student par- others. ticipatedin seven differentlaboratory exercises based 22. Cell membranes are semipermeable. on the propositional knowledge statements that de- Figure 1. Propositionalknowledge statements requiredfor fined the content boundaries of the DODT. The understanding diffusion and osmosis. exercise included activities on the following:

1. Diffusion-of a solid in a liquid The DODT consists of 12 items (Appendix A, pp. 2. Effect of temperatureand concentration on dif- 414-415). The conceptual areas covered by the test are: fusion rates the particulate and random nature of matter, concen- 3. Diffusion through membranes tration and tonicity, the influences of life forces on 4. Osmosis diffusion and osmosis, the kinetic energy of matter, the 5. Consequences of osmosis in a closed system process of diffusion, and the process of osmosis. 6. Water uptake by plant cells An item was scored correct on the DODT if both 7. Observations of the central vacuole in Elodea the desired content and reason answer were selected. Items were evaluated for both correct and incorrect (Summers 1988). The labs were followed by discus- response combinations selected. Table 1 is an exam- sions. ple of an item that tests understanding of the partic- All of the students who participatedin the study ulate and random nature of matter. The desired were selected' with a random number table. The content answer was selected by 63% of secondary secondary students were taught by a secondary biol- students, 62% nonbiology majors, and 74% of biology ogy teacher wzhowas also a Presidential Awardee. majors, while only 35%, 21% and 40%, respectively, The university students were taught by graduate selected the desired content answer and reason com- teaching assistants in the laboratory sections and bination. biology professors in the lecture sections.

410 THEAMERICAN BIOLOGY TEACHER, VOLUME 57, NO. 7, OCTOBER1995 Table 1. The percentage of secondary biology students, nonbiology majors and biology majors selecting each response combinationfor item 3 on the Diffusion and Osmosis Diagnostic Test. As the differencein concentrationbetween two areas increases, the rate of diffusion: (a) Decreases (b) Increases Reason (a) There is less room for the particles to move. (b) If the concentrationis high enough, the particleswill spread less and the rate will be slowed. (c) The molecules want to spread out. (d) The greater likelihood of random motion into other regions. Reason Choiceon first tier a b c d Total Secondary Biology a 9.5 19.8 5.2 2.6 37.1 b 8.6 5.2 13.8 35.3* 62.9

Nonbiology Majors a 8.9 18.7 4.9 5.7 38.2 Downloaded from http://online.ucpress.edu/abt/article-pdf/57/7/409/47314/4450030.pdf by guest on 30 September 2021 b 8.9 4.1 27.6 21.1* 61.8 Biology Majors a 5.1 12.8 5.1 2.6 25.6 b 1.7 3.4 29.1 40.2* 74.4 * Correctchoice and reason

Results of diffusion and osmosis concepts. Secondary stu- 12 The split-half reliability of the DODT among the dents scored 75% on one out of items, nonmajors sample population was 0.74. Majors had fewer mis- scored above 75% on two out of 12 items, and majors conceptions than nonmajors and secondary students scored above 75% on three out of 12 items on the on the DODT. A two-way analysis of variance indi- DODT. cated a significant difference between classes [sec- Major misconceptions were detected in six of the ondary students, nonbiology majors and biology ma- seven conceptual areas covered by the test: the par- jors (p = 0.000)]. There was no significant difference ticulate and random nature of matter, concentration between gender and no interaction between gender and tonicity, the influences of life forces on diffusion and class. A post hoc-Tukey test of significance and osmosis, the process of diffusion, and the pro- indicated that there was no significant difference cess of osmosis. Table 3 is a list of the most common between secondary students and nonbiology majors misconceptions detected by the DODT. (p = 0.961). There was a significant difference between biology majors and secondary/nonbiologyma- Table 2. Percentages of secondary biology students, jors (p = 0.000). college nonbiology and biology majors selecting the According to Gilbert (1977), if a multiple-choice desired content choice and combination content choice item has four to five distractors, understanding is and reason on the Diffusion and Osmosis Diagnostic considered satisfactory if more than 75% of the stu- Test. dents answer the item correctly.In a typical multiple- Secondary Nonbiology Biology choice test with four possible selections, there is a 25% chance of guessing the correct answer. For a DODT Biology Majors Majors Item content reason* content reason* content reason* two-tier item with two selections on the first tier and four selections on the second tier, there is a 12.5% 1 78.4 59.5 72.5 52.8 80.3 58.1 chance of guessing the correct answer combination. 2 86.5 38.8 90.2 22.0 89.7 23.1 The range of correctanswers for the first tier of the 3 62.9 35.3 61.8 21.1 74.4 40.2 4 81.0 35.3 89.9 50.4 92.3 64.1 test was 36% to 87% for secondary students, 36% to 5 39.7 34.5 37.4 34.1 37.6 36.8 98% for nonbiology majors, and 38% to 96% for 6 83.6 50.0 88.6 65.9 94.0 76.1 biology majors (Table2). When both tiers were com- 7 85.4 75.0 97.6 95.9 94.0 92.3 bined, the correctresponses were reduced to a range 8 67.2 33.6 51.2 14.6 64.1 28.2 of 32%to 75%for secondary students, 15%to 81%for 9 72.4 45.7 69.9 44.7 89.7 83.8 10 84.5 43.1 80.5 40.7 95.7 70.9 nonbiology majors, and 23% to 92% for biology 11 36.2 31.9 35.8 31.7 55.6 52.1 majors. 12 84.5 71.6 95.1 81.3 95.7 92.3 The DODT results suggest that students at all * content and reason combination levels did not acquire a satisfactory understanding

DIFFUSION& OSMOSIS 411 Table 3. Percentages of responses by secondary biology students, college nonbiology and biology majors with specific misconceptions detected by the Diffusion and Osmosis Diagnostic Test. Secondary Nonbiology Biology Misconceptions Biology Majors Majors Item TheParticulate & RandomNature of Matter 1. Particlesmove from high to low concentrationbecause: a. They tend to move until the two areas are isotonic and then the particles stop moving. 22.4 32.5 33.3 2 b. There are too many particles crowded into one area, therefore they move to an area with more room. 18.9 31.7 26.5 2 2. As the differencein concentrationincreases between two areas, rate of diffusion: a. Increases because the molecules want to spread out. 13.8 27.6 29.1 3 b. Decreases because if the concentrationis high enough, the particles will spread less and the rate will be slowed. 19.8 18.7 12.8 3 3. When a drop of dye is placed in a containerof clear water the: a. Dye molecules continue to move around because if dye molecules stopped, they would settle to the bottom of the container. 26.7 13.0 6.0 6 Downloaded from http://online.ucpress.edu/abt/article-pdf/57/7/409/47314/4450030.pdf by guest on 30 September 2021 b. Dye molecules continue to move around because this is a liquid; if it were solid the molecules would stop moving. 3.5 6.5 11.1 6 Concentration& Tonicity 1. A glucose solution can be made more concentratedby adding more glucose because the more water there is, the more glucose it will take to saturate the solution. 26.7 22.0 20.5 4 2. Side 1 is 10%salt solution and side 2 (15%salt solution). a. Side 1 is hypotonic to Side 2 because water moves from high to low concentration. 19.8 15.4 6.0 9 b. Side 1 is hypertonic to Side 2 because the water moves from high to low concentration. 7.8 10.6 3.4 9 TheInfluence of LifeForces on Diffusion& Osmosis 1. If a plant cell is killed and placed in a salt solution, diffusion and osmosis will not occur because the cell will stop functioning. 25.0 26.8 22.2 11 TheProcess of Diffusion 1. The process responsible for a drop of blue dye becoming evenly distributed throughout a container of clear water is: a. Diffusion because the dye separates into small particlesand mixes with water. 17.2 18.7 20.5 1 b. Osmosis because there is movement of particlesbetween regions of differentconcentrations. 11.2 14.6 5.1 1 2. When sugar is added to water, after a very long period of time the sugar will be more concentratedon the bottom of the containerbecause: a. There will be more time for settling. 10.3 25.2 7.7 5 b. The sugar is heavier than water and will sink. 26.7 22.0 40.2 5 c. Sugar dissolves poorly or not at all in water. 11.2 8.9 12.8 5 TheProcess of Osmosis 1. Two columns of water are separated by a membrane through which only water can pass. Side 1 contains dye and water; Side 2 contains pure water. After two hours, the water level in Side 1: a. Will be higher because water will move from the hypertonic to the hypotonic solution. 13.8 22.0 16.2 8 b. Will be higher because water moves from low to high concentration. 18.9 13.0 15.4 8 c. Will be lower because water will move from the hypertonic to hypotonic solution. 12.1 14.6 14.5 8 d. will be the same because water will become isotonic. 1.7 17.1 13.7 8 2. If a freshwater plant cell was placed in a beaker of 25% salt water solution, the central vacuole would decrease in size because salt absorbs the water from the central vacuole. 31.9 35.8 19.7 10

Discussion & Conclusions instructional approaches to hopefully correct these This study provides evidence that even following misconceptions. instruction secondary biology students, nonbiology Similarly,Zuckerman (1993) identified 12 accurate and biology majors continue to have misconceptions conceptions of osmosis. In addition, she identified about diffusion and osmosis. The identification is of eight misconceptions about osmosis held by high direct relevance for secondary and college biology school science students. It was reported that miscon- teachers since this knowledge can be used to develop ceptions about osmosis blocked problem solving of

412 THEAMERICAN BIOLOGY TEACHER, VOLUME 57, NO. 7, OCTOBER1995 osmosis-relatedquestions. Two misconceptions were ute to learning. Different students will respond specificallylinked with blocking meaningful problem to different techniques. solving: the rate of osmosis is constant, and the In conclusion, an important outcome of this re- concentrationsof water across the membranemust be search study is the extent to which biology concepts equal at osmotic equilibrium. Of the 12 accurate in diffusion and osmosis are not being comprehended conceptions, two were especially important in en- by students from secondary and university cam- abling problem solvers to generate correct answers: puses. Based on the results of this study, biology increasing the height of the column of a solution teachersappear not to be teaching for comprehension increases the hydrostaticpressure on the membrane; of diffusion and osmosis concepts, but rather for and when a solution and water are separated by a emphasizing the acquisition of facts (although there selectively permeable membrane, pressure against were no direct observations of instruction). Further, the solution side of the membrane opposes osmosis. the DODT can be a valuable tool that can aid teachers Odom and Settlage (1994) reported that formal in assessing both their teaching methodologies and reasoning played a significant role in understanding students' understanding and reasoning about diffu- diffusion and osmosis concepts. They found that sion and osmosis. formal high school students out performed pre- Downloaded from http://online.ucpress.edu/abt/article-pdf/57/7/409/47314/4450030.pdf by guest on 30 September 2021 formal high school students on five out of seven concepts related to diffusion and osmosis: particulate References and random nature of matter, concentration and Christianson,R.G. & Fisher, K.M. (1994).Analysis of student tonicity, membranes, the process of diffusion, and learningabout diffiusion and osmosisin threedifferent biology classesusing Odomand Barrow'sDiagnostic Test. Unpub- the process of osmosis. In addition, they found grade lished manuscript. level to be an insignificant covariate, and in most Friedler, Y., Amir, R. & Tamir, P. (1987). High school cases formal 10th grade students out performed pre- students' difficultiesin understanding osmosis. Interna- formal 11th and 12th grade students. Similarily,Ren- tionalJournal of ScienceEducation, 9, 541-551. Gilbert,J.K. (1977). The study of student misunderstand- ner and Marek (1988)noted that the large majorityof ings in the physical sciences. Researchin ScienceEducation, high school students were pre-formal reasoners. In 7, 165-171. their study, 90%of the 10th graders, 76%of the 11th Gorjanc-Barthel,M. (1989). High schoolchemistry students' graders, and 68% of the 12th graders were pre- misconceptionson covalentbonding and structure.Unpub- lished master's thesis, University of Missouri-Columbia. formal. The results of these two studies suggest that Haslam, F. & Treagust, D.F. (1987). Diagnosing secondary specially designed instructional approaches should students' misconceptionsof photosynthesis and respira- be used if diffusion and osmosis are going to continue tion in plants using a two-tier multiple choice instru- to be part of the secondary curriculum.Further, the ment. Journalof BiologicalEducation, 21, 203-211. Kiokaew, S. (1989). Collegefreshman's concepts of covalent approaches should include instructional strategies bonding.Unpublished doctoraldissertation, University of that allow students concrete interaction with diffu- Missouri-Columbia. sion and osmosis concepts and should follow a se- Odom, A.L. & Settlage, J. (1994). High school students' quence that focuses on the learning cycle model of understandingof diffusionand osmosisconcepts in relationto theirlevels of cognitivedevelopment. Paper presented at the instruction. annual meeting of the National Association of Research Christianson and Fisher (1994) reported that col- in Science Teaching, Anaheim, CA, March26-29, 1994. lege students in a "constructivist" course learned Odom, A.L. & Barrow, L.H. (in press). The development significantly more diffusion and and application of a two-tier diagnostic test measuring osmosis concepts college biology students' understandingof diffusion and than students in a more traditionalbiology course. It osmosis following a course of study. Journalof Researchin was suggested that motivation and learning in biol- Science Teaching. ogy could be enhanced by: Peterson, R.F. (1986). Thedevelopment, validation and appli- cationof a diagnostictest measuringyear 11 and 12 students' understandingof covalentbonding and structure.Unpub- 1. Allowing teacher-student and student-student lished master's thesis, Curtin University of Technology, discussion. Western Australia. 2. Allowing time for prediction. Once students Renner, J.W. & Marek, E.A. (1988). Thelearning cycle and elementaryschool teaching. Portsmouth, NH: Heinemann. have been presented with a body of informa- Summers, G. (1988). Laboratoryexercises in generalbiology. tion, they need opportunities to apply that in- Edina, MN: Burgess Publishing Company. formationin order to weed out misconceptions, Treagust, D.F. (1985). Diagnostictest to evaluatestudents' reinforceunderstanding, and make predictions. misconceptionsin science.A paper presented at the 58th Annual Meeting of the National Associationfor Research 3. Using concept mapping to anchor concepts and in Science Teaching. FrenchLick Springs, Indiana, April construct meaning. 15-18, 1985. 4. Using the best teaching method-a variety of Zuckerman, J.T. (1993). Accurateand inaccurateconceptions methods. Lecture, discussion, laboratory dem- aboutosmosis that accompaniedmeaningful problem solving. Paper presented at the annual meeting of the National onstration, prediction, consensus building, and Association for Research in Science Teaching, Atlanta, computer organizationof knowledge all contrib- GA, April 17, 1993.

DIFFUSION& OSMOSIS 413 Appendix A

Diffusion & Osmosis Test Directions:DO NOT WRITEON THE ASSESSMENT.This assessment consists of 12 pairs of questions that examine your knowledge of diffusion and osmosis. Each question has two parts: a multiple choice response followed by a multiple choice reason. On the answer sheet provided, please circle one answer from both the response and reason sections of each question.

la. Suppose there is a large beaker full of clear 4a. A glucose solution can be made more concen- water and a drop of blue dye is added to the trated by: beaker of water. Eventually the water will a. Adding more water turn a light blue color. The process responsi- b. Adding more glucose ble for blue dye becoming evenly distributed 4b. The reason for my answer is: throughout the water is: a. The more water there is, the more glucose Downloaded from http://online.ucpress.edu/abt/article-pdf/57/7/409/47314/4450030.pdf by guest on 30 September 2021 a. Osmosis it will take to saturate the solution. b. Diffusion b. Concentration means the dissolving of c. A reaction between water and dye something. lb. The reason for my answer is: c. It increases the number of dissolved parti- a. The lack of a membrane means that osmo- cles. sis and diffusion cannot occur. d. For a solution to be more concentrated, b. There is movement of particles between one must add more liquid. regions of different concentrations. 5a. If a small amount of sugar is added to a c. The dye separates into small particles and container of water and allowed to set for a mixes with water. very long period of time without stirring, the d. The water moves from one region to an- sugar molecules will: other. a. Be more concentrated on the bottom of the 2a. During the process of diffusion, particles will container generally move from: b. Be evenly distributed throughout the con- a. High to low concentrations tainer b. Low to high concentrations 5b. The reason for my answer is: 2b. The reason for my answer is: a. There is movement of particles from a high a. There are too many particles crowded into to low concentration. one area, therefore they move to an area b. The sugar is heavier than water and will with more room. sink. b. Particlesin areasof greaterconcentration are c. Sugar dissolves poorly or not at all in more likely to bounce toward other areas. water. c. The particles tend to move until the two d. There will be more time for settling. areas are isotonic and then the particles 6a. Suppose you add a drop of blue dye to a stop moving. container of clear water and after several d. There is a greater chance of the particles hours the entire container turns light blue. At repelling each other. this time, the molecules of dye: 3a. As the difference in concentration between a. Have stopped moving two areas increases, the rate of diffusion: b. Continue to move around randomly a. Decreases 6b. The reason for my answer is: b. Increases a. The entire container is the same color; if 3b. The reason for my answer is: the dye molecules were still moving, the a. There is less room for the particlesto move. container would be different shades of b. If the concentration is high enough, the blue. particles will spread less and the rate will b. If the dye molecules stopped, they would be slowed. settle to the bottom of the container. c. The molecules want to spread out. c. Molecules are always moving. d. The greater likelihood of random motion d. This is a liquid; if it were solid the mole- into other regions. cules would stop moving.

414 THEAMERICAN BIOLOGY TEACHER, VOLUME 57, NO. 7, OCTOBER1995 7a. Suppose there are two large beakers with amounts of clear water at two different equal BEAKER1 BEAKER2 temperatures. Next, a drop of green dye is 25C 35L added to each beaker of water. Eventually the water turns light green (see Figure 1). Which Figure 1 beaker became light green first? a. Beaker 1 SIDE1 SIDE2 b. Beaker 2 DYE AND WATER 7b. The reason for my answer is: WATER a. The lower temperaturebreaks down the dye. b. The dye molecules move faster at higher MEMBRANE.A temperatures. Figure2 c. The cold temperature speeds up the molecules. SIDE1 SIDE2 d. It helps the molecules to expand. 10% 15% Downloaded from http://online.ucpress.edu/abt/article-pdf/57/7/409/47314/4450030.pdf by guest on 30 September 2021 8a. In Figure 2, two columns of water are sepa- Salt Salt rated by a membrane through which only Solution Solution water can pass. Side 1 contains dye and water; MEMBRANE, Side 2 contains pure water. After two hours, Figure 3 the water level in Side 1 will be: a. Higher b. Lower c. The same height Central Membrane 8b. The reason for my answer is: * Vacuoile Cl a. Water will move from the hypertonic to Wall hypotonic solution. * ~~~(Fresh b. The concentration of water molecules is Water) less on Side 1. Figure 4 c. Water will become isotonic. d. Water moves from low to high concentra- lla. Suppose you killed the plant cell in Figure tion. 4 with poison and placed the dead cell in a 9a. In Figure 3, Side 1 is __ to Side 2. 25% salt water solution. Osmosis and dif- a. Hypotonic fusion would: b. Hypertonic a. Not occur c. Isotonic b. Continue 9b. The reason for my answer is: c. Only diffusion would continue a. Water is hypertonic to most things. d. Only osmosis would continue b. Isotonic means "the same." llb. The reason for my answer is: c. Water moves from a high to a low. a. The cell would stop functioning. d. Thereare fewer dissolvedparticles on Side 1. b. The cell does not have to be alive. lOa. Figure 4 is a picture of a plant cell that lives in c. Osmosis is not random, while diffusion fresh water. If this cell was placed in a beaker is a random process. of 25% salt water solution, the central vacuole d. Osmosis and diffusion require cell en- would: ergy. a. Increase in size 12a. All cell membranes are: b. Decrease in size a. Semipermeable c. Remain the same size b. Permeable lOb. The reason for my answer is: 12b. The reason for my answer is: a. Salt absorbs the water from the central a. They allow some substances to pass. vacuole. b. They allow some substances to enter, b. Water will move from the vacuole to the but they prevent any substance from salt water solution. leaving. c. The salt will enter the vacuole. c. The membrane requires nutrients to d. Salt solution outside the cell cannot effect live. the vacuole inside the cell. d. They allow ALL nutrients to pass.

DIFFUSION& OSMOSIS 415