Class time required: Approximately 20 minutes of homework followed by 80 minutes of class time

Transcription

1 Activity 3: Nan Particles Key Cncept: Small particles have a greater surface area per unit mass and have increased ptential fr bilgical interactins that may lead t health prblems. Class time required: Apprximately 20 minutes f hmewrk fllwed by 80 minutes f class time Teacher Prvides: Optinal: 1 cpy f the bk Zm by Istvan Banyai (available at Als cnsider the bk Rezm by the same authr. Tear the pages ut f the bk and ask students t arrange them in rder frm largest view t smallest view. A cpy f student handut Nan Particles fr each student. Fr each team f students Zip tp clear plastic sandwich bag cntaining 8 plastic centimeter cubes per team. It is imprtant that all f the cubes in this bag are the same clr. Plastic cubes can be rdered frm Apprximate cst is $15.00 fr 500 cubes. Yu may als substitute sugar cubes fr this activity. Zip tp clear plastic sandwich bag (use gd quality bags) labeled Large cntaining 1 gram (apprx 1/3 teaspn) carse gel granules. Granules may be rdered frm Select the carse size gel granules. Apprximately cst is $6.00 fr a 12 unce (340 grams) bag. Zip tp clear plastic sandwich bag (use gd quality bags) labeled Small cntaining 1 gram (apprx 1/3 teaspn) f medium gel granules. Granules may be rdered frm Select the medium size gel granules. Apprximate cst is $6.00 fr a 12 unce (340 grams) bag. Plastic 1 ml graduated drpper fr measuring the Blue Dye slutin. Cup r beaker labeled Water that cntains at least 100 ml f tap water. Small cntainer (test tube r beaker) labeled Blue Dye that cntains at least 5 ml f 0.1% brmthyml blue slutin. Order frm (catalg number 944 V 7106). Apprximate cst f 500 ml bttle is $ Add 3 drps f husehld ammnia t each 10 ml f brmthyml slutin t keep the brmthyml frm turning green when mixed with water and gel granules. Small cntainer (test tube r beaker) labeled Acid that cntains at least 60 ml f white vinegar. Purchase vinegar at a lcal grcery stre. 50 ml graduated cylinder r 1 unce plastic medicine cup with ml markings. 1

2 Suggested Class Prcedure: Optinal: Shw selected pages frm the bk Zm (ging frm large t small) t illustrate the fact that when yu lk at smaller and smaller things, the types (r details) f prcesses yu can see change. Distribute cpies f the student handut entitled Nan Particles t each student. Distribute t each team f students. Bag labeled Small cntaining 1 gram f the medium granules. Bag labeled Large cntaining 1 gram f carse granules. Tube f Blue Dye 1 graduated (1 ml) plastic drpper Cup labeled Water that cntains tap water. 50 ml graduated cylinder r 1 unce plastic medicine cup with ml markings. Students cmplete the Intrductin. It takes abut ½ hur fr the granules t cmpletely absrb the blue dye. Yu may either have students: Cmplete the intrductin and then wait until the next class t cmplete the ther parts f this activity, OR Wrk n Part 1 and Part 2 t allw time fr the granules t absrb the blue dye. This allws time fr the granules t absrb the blue dye cmpletely befre they d Part 3. Students t read the infrmatin in Part 1 and answer the questins in Part 1 while the granules are absrbing the blue dye. Distribute t each team f students. Bag cntaining 8 plastic centimeter cubes (r sugar cubes) Students t read the infrmatin in Part 2 and answer the questins in Part 2 while the granules are absrbing the blue dye. Distribute t each team f students. Tube r cup r beaker labeled Acid that cntains white vinegar Cup labeled Water that cntains tap water. 50 ml graduated cylinder r 1 unce plastic medicine cup with ml markings. Distribute tubes f Acid (vinegar) t students. Students cmplete Parts 3. When students have cmpleted Part 3, they shuld be instructed t discard the bags cntaining fluid and gel particles int a waste cntainer. DO NOT dispse f the cntents f the gel bags in the sink. 2

3 Extensins: Ask students fr ther real-life examples in which small particles react differently than larger particles. Yu culd mdel ne answer such as yu can fit mre kindergarteners than adults int a car r fine pwdered sugar disslves mre rapidly than a sugar cube. Ask students t explain hw this activity culd be used t explain why they are made f millins f micrscpic cells rather than ne large cell. This prject was generusly funded by Science Educatin Partnership Award R25RR frm the Natinal Center fr Research Resurces. The cntent is slely the respnsibility f the authrs and des nt necessarily represent the fficial views f the Natinal Center fr Research Resurces r the Natinal Institutes f Health. 3

4 Nan Particles Intrductin In this activity, yu will use gel particles t explre hw particle size affects tw particle behavirs - absrbing and reacting. Each f the tw small plastic bags cntains 1 gram f particles. 1 gram f particles 1. Bth f the bags cntain the same mass f particles (1 gram). Which bag cntains the largest number f particles per gram large particles r small particles? Small particles 2. Use the small measuring cup t add 40 ml f water t each f the bags. Set each f the bags int cups t keep them frm falling ver. 3. Use the graduated plastic drpper t add 2 ml f blue dye t each f the bags. 1 ml mark 4. Seal the bags t prevent spills. 5. Observe the bags after 2 minutes. Which size f particles absrbed the blue dye slutin mre rapidly small particles r large particles? The small nes 6. G n t cmplete Parts 1 and 2 while yu wait fr all the particles t cmpletely absrb the blue dye. 4

5 Part 1: Particles in the air yu breathe The particles fund in air pllutin that yu inhale cme in many different sizes. The size f inhaled particles determines hw deeply they can penetrate the respiratry tract. Large particles Larger particles (10-30 micrmeters) are usually filtered by the nse and thrat. Alvelus Capillaries PM 2.5 Particles smaller than abut 2.5 micrmeters, referred t as PM 10, can mve int the trachea, brnchi and brnchiles. Nanparticles Particles smaller than 0.1 micrmeters, referred t as nanparticles, can easily mve int the alveli and the capillaries and then accumulate in ther rgans, including the brain. Research studies have shwn that inhaling PM 2.5 particles significantly increases the risks fr respiratry diseases (such as asthma, emphysema, and lung cancer) and cardivascular diseases (such as heart disease and strkes) particularly fr peple with pre-existing cnditins. Scientists are cncerned that nanparticles that are less than 100 nanmeters may be mre damaging t the respiratry and cardivascular system than PM 2.5. There is sme evidence that nanparticles can mve frm the respiratry system int the capillaries. Nanparticles culd be circulated t and accumulate in ther rgans, including the brain. Scientists pint ut that there is an urgent need fr research t determine the rle f nanparticles in cardivascular disease and respiratry disease. 1. T what des PM 2.5 refer? Particles which are smaller than 2.5 micrmeters. 2. A nanparticle is smaller than 100 nanmeters r 0.1 micrmeters. What subscript shuld yu use t express this as particulate matter size? PM 0.1 5

6 3. List at least tw cardivascular prblems and tw respiratry prblems that have been shwn t be assciated with particles smaller than 2.5 micrmeters (2,500 nanmeters), PM 2.5. Cardivascular prblems Heart attack and strke Respiratry prblems asthma, emphysema, and lung cancer. 4. List all parts f the respiratry system in which yu might find nanparticles? Hint: See the diagram n page 2. The nse, thrat, trachea, brnchi, brnchiles, alveli, and capillaries in the lungs 5. Explain hw it is pssible t find inhaled nanparticles in ther rgans f the bdy such as the brain and the liver. Nanparticles are small enugh t enter bld vessels and be circulated thrughut the bdy. 6. Why are scientists cncerned that nanparticles (particles that are less than 100 nanmeters) may be an even greater health prblem than PM 2.5 particles? There is evidence that particles smaller than 100 nanmeters can pass thrugh pass thrugh the membranes f the alveli int the capillaries and then be circulated t and accumulate in ther rgans, including the brain. 6

7 Part 2: Particle Size and Surface Area Nanparticles absrb and react mre rapidly than larger particles, because they have mre surface are per unit vlume. In this activity, yu will use plastic cubes t help yu visualize the relatinship between particle size, vlume and surface area. 1. Use the 8 small cubes t build a large cube that is 2 cm X 2 cm X 2 cm. 2 cm Each f the small plastic cubes has a mass f 1 g (gram) and has a vlume f 1 cm 3 (cubic centimeter). 1 cm Vlume = length x width x height Surface area f cube = length x width x 6 2. Cmplete nly Clumn 1 (1 Large Cube) n the data table. Yu will use the instructins and hints n the next tw page t cmplete Clumns 2 and 3. Hints: The large cube shuld be cunted as 1 particle. Use the infrmatin in the bx abve. Clumn 1 Clumn 2 Clumn 3 1 Large Cube (2 X 2 X 2 cm) 8 Small Cubes (1 X 1 X 1 cm each) 8,000 Tiny Cubes (1 X 1 X 1 mm each) Number f particles 1 8 8,000 Ttal Mass (grams) Ttal Vlume (cm 3 ) Ttal Surface area (cm 2 )

8 3. Separate the cubes s that there are 8 small cubes. Cmplete Clumn 2 (8 Small Cubes) n the data table. Base yur calculatins n the ttal fr all eight cubes. Hint: Each small cube shuld be cunted as ne particle. Calculate the surface area fr ne cube and then multiply by Imagine that each f the centimeter cubes was cut int tiny cubes that were 1 millimeter X 1 millimeter X 1 millimeter. Yu culd fit 1,000 f the millimeter cubes int a ne small cube. Yu culd fit 8,000 f these tiny cubes int a large cube! The ttal surface area f 8,000 f these tiny cubes wuld be 480 cm 2 (Nte: the surface area f ne side f this sheet f paper is 580 cm 2 ). Use this infrmatin t cmplete Clumn 3 (8,000 Tiny Cubes) n the data table. If yu culd cut ne f the small plastic cubes int nancubes, the ttal surface area f these nancubes wuld be equal t the surface area f 4 hckey rinks!!! If yu culd cut all eight f the small plastic cubes int nancubes, the ttal surface area f these nancubes wuld be equal t the surface area f 32 hckey rinks!!! 5. What is the mst imprtant thing that yu learned frm this cube activity? Student answers will vary but shuld indicate cutting large particles int many small particles increases the surface area. 8

9 Part 3: Particle Behavir tw bags f blue particles The issue with nanparticles is nt simply hw easily they enter the bdy. Once nanparticles enter the bdy they behave differently frm larger particles f the same material. In this activity, yu will bserve and cmpare the behavir f large particles and small particles that are placed in acid. When yu add acid t the bags f blue gel granules, the blue gel granules turn yellw when they absrb and react with the acid 1. Use the small measuring cup t add 25 ml f acid t each f the bags f blue gel granules. 2. When the particles react with acid, they turn yellw. Which particles reacted mst rapidly with the acid small particles r large particles? The small particles turned yellw mre rapidly than the larger nes. 3. Use what yu learned in Part 2 (the cube activity) t explain why small particles absrbed and reacted mre rapidly. Small particles have much mre surface area fr absrbing and reacting. The blue gel particles that yu used in these experiments were large enugh t be seen with the naked eye. The small gel particles were apprximately 1 millimeter acrss. If measured in micrmeters the diameter f the small particle wuld be 1,000 micrmeters r 1,000,000 nanmeters. A nanparticle is an extremely small particle that is less than 100 nanmeters in size. Yu culd line up 10,000 nanparticles acrss the diameter f ne small particle. Small blue gel particle 10,000 nanparticles wuld fit in a line acrss the diameter f ne small gel particle 4. Yu dn t need t d the calculatins t determine the answers t these questins. Just use yur imaginatin! If yu had a bag that cntained ne gram f nanparticles, Imagine hw many nanparticles the bag wuld cntain. Millins and millins! Imagine hw rapidly the nanparticles wuld absrb the blue dye. Extremely rapidly in a fractin f a secnd! Imagine hw rapidly the nanparticles wuld react with substances arund them. Extremely rapidly in a fractin f a secnd! 9

10 EPA Air Quality Standards Air particle pllutin, als called particulate matter r PM, is a cmplex mixture f extremely small particles and liquid drplets in the air. When breathed in, these particles can reach the deepest regins f the lungs. Expsure t air particle pllutin is linked t a variety f significant health prblems, ranging frm aggravated asthma t premature death in peple with heart and lung disease. T prtect public health and welfare, the US Envirnmental Prtectin Agency (EPA) issues air quality standards fr particulate matter. Accrding t the 2006 EPA air quality standards, the cncentratin f inhalable carse particles (PM 10 ) in air shuld be less than 15 micrgrams per cubic meter. The cncentratin f fine particles (PM 2.5 ) shuld be less than 65 micrgrams per cubic meter. Sme scientists are cncerned that the EPA standards fr air pllutin, which are expressed in terms f mass (micrgrams), are nt a prper measure f the health hazards f very tiny particles such as nanparticles. They pint ut, fr example, that 1 millin nanparticles have abut the same mass as ne large particle f 10 µm diameter. These scientists suggest that particle number r particle surface area per cubic meter f air wuld be mre effective measures f the ptential fr small particles t cause health prblems. Surce: 5. Why is a micrgram (µg) f nanparticles mre likely t lead t cardivascular disease than a micrgram (µg) f larger particles? Because 1 millin nanparticles have abut the same mass as ne particle f 10 µm diameter. OR There are many mre particles (r surface area) in ne gram f nanparticles than there are in ne gram f 10 µm diameter particles. 6. What measurement standard might be a mre effective measure f the ptential fr small particles t cause health prblems? Particle number r particle surface area per cubic meter might be a mre effective measure f the ptential fr small particles t cause health prblems. 10