LearningForward

Kent Chesnut's technology in education blog.

My youngest son’s 7th grade Science class just finished a chapter on cell division and DNA.  DNA Replication is a key concept in cell division.  Each strand of DNA divides into 2 half-strands (which are not identical).  Then each half reconnects with free bases within the cell to for 2 new strands of DNA which are identical to the original strand.

Key Concepts:

• There are 4 bases the are used to make the rung of the DNA double helix “ladder”.
• 2 bases combine to form each rung.
• The 4 bases are Adenine (A), Thymine (T), Guanine (G), and Cytosine (C).
• Adenine binds only with Thymine (A-T or T-A) to form a rung.
• Guanine binds only with Cytosine (G-C or C-G) to form a rung in the DNA ladder.

 My goal with this project was to consider what type of a constructivist / constructionist project a 7th grade student could generate to help them understand the concept of DNA replication.  I utterly failed at this - instead ended up investigating the capabilities of Scratch to build a game like activity to illustrate DNA replication.

A screenshot of the project is shown at the right.  Run the project by clicking here.  Download the project file here.

OK, so the project does make an activity that students could use to practice DNA replication and, hopefully, understand how the DNA strand can replicate itself.  But why was the project a failure?  Because it’s way too difficult for a 7th grader!

I believe the following parts of the program to be much too difficult for a typical 7th grader:

• Checking to see if the strand is reconstructed correctly.  Have a look at the “when I receive Checkit” block in each of the Rightx sprites.
• The concept of constructing the bases as generic left and right, each one having a state (essentially the base type T,A,C,G) controlled by a variable.
• Randomizing the DNA strand each time the program is run requires the state concept above and is beyond the reach of most 7th graders.

Suppose a 7th grader actually wanted to create a project like this?  What could (s)he make?  I’m speculating here - but I suggest that such a project created by a 7th grade Science student in a reasonable time (say 2 hours) could have the following attributes:

• Starts with a full DNA strand that looks something like the one in my project.
• Rips the DNA strand apart leaving the right side as 9 separate sprites that retain their type (T,A,C,G).
• Allow the user to drag the right sprites onto the left strand.
• Provide instructions for the user to follow to check to see if the DNA strand has be replicated properly.

I want to consider here the great constructivist / instructivist debate.  Which is more valuable for the student when trying to learn the basics of DNA replication?

A. Practice DNA replication a few times by running a more automated activity like I created  (Instructivist approach).

• Very efficient in terms of time… student can practice the process many times in the 2 hours that it would take build the simpler project himself.
• The puzzle nature of the activity will be engaging to some students.
• There’s no guarantee that running the program even a large number of times will result in the student attaching biological meaning to what he is doing.
• Probably the better approach if the instructional objective is for the student to be able to fill in a DNA chain on a test.

B. Create the less capable project… essentially having to learn the DNA replication process to be able to build the project (Constructivist approach) and having the project available as an artifact to discuss / explain DNA replication (Constructionist approach).

• Students may get too bound up in the Scratch implementation to really think about what is happening biologically.
• Will take longer than simply running the activity.
• Students who complete the project will probably have a better understanding of DNA replication than those who ran the program.  I believe this is true and that the main cause of the better understanding would be the thinking and planning that go into building an interaction to illustrate DNA replication.
• Probably the better approach if the instructional objective is for the student to be able to describe to others how DNA replication works.

I’d be really interested in any reader response to this analysis.  What do you think?  And if you’re a teacher, which would you rather have (the instructivist activity or the constructivist project) and why.

Oops!  I apologize for the misspellings in the project file… I think I fixed them in the post.

One of the things I would really like to achieve in my lifetime is to improve the educational outcomes for a significant number of kids.  To this end I read and study educational theories.  I teach informal educational classes (like the Scratch Class last week).  But I’m not making the impact I’d like to have.  So I continue to look for groups who have similar / compatible goals - maybe I could work with them???

A few weeks ago I read about e-Learning for Kids.  The following quote is from the e-Learning for Kids about us page…

“In today’s complex world, children’s futures are determined by their ability to master the basics of reading, science, math and computers. Yet costs, class sizes and other issues often prevent children access to quality online learning that can support and reinforce these essential skills.

Our vision is to be the source for childhood learning on the Internet – available from anywhere and without charge. Established in late 2004, e-Learning for Kids is a global, nonprofit foundation dedicated to fun and free learning on the Internet for children ages 5 - 12.”

Wow!  Global vision.  Improved educational outcomes for significant numbers of kids.  On the surface, this group appears to be working in the direction I’d like to pursue. 

I’ve worked through 6 - 8 of the short (20 - 30 minute) courses available on the website.  The lessons appear to be pretty well designed, very supplantive (all of the instructional strategy appears to be built into the lesson itself - as opposed to a generative strategy), and supply very little user control (some do allow user to select the order that information is encountered, but some basically lead the user through the material).

 For example, the featured course at this time is “Science - States of Matter” about solids, liquids and gases.  The lesson is designed as a pretty straightforward concept lesson.  The lesson proceeds as follows:

• Objectives are listed and read by a narrator.
• Professor Beaker introduces himself.  Professor Beaker narrates the remainder of the course.
• The student signs in with his name and age.
• The lesson proceeds along a path, encompassing: “What is Matter?”; ”Changing States of Matter.”;  and “Identifying States of Matter.”  The lesson will progress through these sequentially - or you can jump to a different section at any time.  I’ll assume you allow the lesson to proceed along sequentially.
• What is Matter?  The student is presented with examples of solids, liquids, gases.  The student is not specifically given a list of criteria for determining the state of each example, but hints are given… for example, it is noted that the example liquids will run through your fingers.
• Changing States of Matter.  The student drags a beaker of water to a freezer and then onto a burner to observe it changing states.
• Identifying States of Matter.  The student practices identifying states of matter by dragging items into Solid, Liquid, or Gas category.  When the student presses submit, he is shown the incorrect classifications and allowed to try them again.  When all the items are categorized correctly, the program proceeds to the Summary.
• Summary.  A short summary of what the student has accomplished is presented.

Analysis

• If you’ve read this blog, you know I lean toward constructivism / constructionism.  I would like to see students creating projects that are personally meaningful.  I would like to see students pursuing authentic real world tasks in their studies.  (See my about page here for more details.)  I really don’t think the e-Learning for Kids courses I’ve viewed do this very well.  But is it possible to pre-package such projects and authentic tasks when considering the widely varying cultures of the world?  Or are projects even practical in individualized (no feedback from peers or instructor) eLearning?  I’ll need to do some thinking and investigating on this topic.
• Would such a group even be interested in my participation?

Conclusion

I’ll forgo any decision about instructivism vs. constructivism in the e-Learning for Kids courses for now.  I’d like to see the group’s course development criteria for information / direction on this.

I’ve e-mailed the e-Learning For Kids organization to inquire about their course development criteria.  I assume if they would be interested in my participation, they’ll provide some documetation on how their development process works. 

Note for XO users - OLPC is listed as an NGO Partner on the e-Learning for Kids website.  All of the courses I’ve worked through are Flash based.  I’ve tried several on the XO Laptop.  In most of the courses I’ve tried, the animations are too slow on the XO.

Good grief, where’s the ed tech?  Another reflective post?  What’s up with this? 

Last week, I read and commented on Clay Burrell’s post “How Freedom Can Depress Students“.   Clay discusses research that indicates that “good” school experiences (where students are provided autonomy to make decisions about how they learn and how they demonstrate their learning) may actually be bad for students since such experiences are few and far between.  The premise is that the “normal” classes that will inevitably come will prove depressing.

I personally agreed with the depressing part… but argued that the good experiences are good…  I’ve copied my comment below.

“Clay,
Great article!

What a deal! One of the things I want most for my kids… an educational setting that provides the freedom to allow their intrinsic motivation and love of learning to flourish will make them depressed when that is taken away.

I totally agree that this is true… and have seen it in one of my own children. After a school [year] with some really good experiences, the next year was pretty pathetic.

However, I view the good experience as a good thing… my child now knows what it is like to really enjoy learning. She may not get to enjoy it right at this moment, but she knows that given the right environment she will! She also seems to have a better understanding of what is going on when classes are not any fun… she doesn’t blame herself anyway.

Just my 2 cents… keep up the great articles.
Kent”

As I thought about this a little more, I became disturbed that both Clay and I seemed to accept that the kids are powerless in this situation.  This powerlessness was also portrayed in my prison metaphor in a recent post called “Fix the Kids“.

I’m pretty resolved to the fact that I can’t fix the schools.  So the other alternative is to empower the kids… with a love of learning on their own!  When school is good… that’s great.  When it’s lousy… they will adapt.  When it’s over, they’ll be lifelong learners.  Maybe they’ll be able to fix the schools of the future!

The purpose of this post is to consider this question:

“What can I do, within the school or apart from the school, that can help my children (and others I’m in contact with) develop a love and passion for learning?”

Unfortunately, I don’t have good answers.  But I think the answers will include some of these elements:

• Working with them on interesting projects outside of school (learning Scratch or Logo, building animated stories for Children’s Worship lessons, trying to figure out how to get that PSP to ???, encouraging investigation of constructive software).  The goal is for them to understand that learning can be engaging and relevant, even if school is not.

• Working with them and encouraging them with school projects (science fairs, in class demonstrations, homework, …)

• Being honest… When a class is being taught poorly (highly structured, teacher centered, repressive), let the child know.  When a class is being taught well (learner centered, relevant, cooperative), let them know that too!  (This may not be appropriate for younger students - especially those that might relay your comments to their teacher!!… but how young is too young?)

• Treating school as important… but being careful to make sure that they know their value is not tied to school performance.  And making sure that they know that there is plenty of valuable learning that takes place outside of school.

I’ll be considering this further… but would love to hear any ideas a reader might have.

This week I was asked to serve as a “harsh reader” for a grant application for a  local school.  Although I don’t know anything about grant applications (and I explained this to the requester), I did think it would be interesting to read one… so I read through and provided input where I thought it might help (I only hope I wasn’t too harsh ;-).

This was Wednesday.  By Thursday I was thinking about the grant application and its assumptions.  I certainly can’t describe the whole grant, but I’ll give an overview.  A couple of junior high schools in this district have significantly higher rates of suspension and performance gaps than the state average.  The grant proposal is to hire a graduation coach for each of these 2 schools.  The purpose of the coach will be to identify students who (according to certain criteria) are likely to be drop outs before graduation, design and implement intervention and incentive programs to keep them in school.  These at-risk students were described as disengaged in school and having behavioral problems and numbered somewhere between 13% - 25% of the schools’ populations.

It all seemed so reasonable… until I started thinking about the underlying assumptions.  These students don’t see any value in school, they haven’t been successful there, school has no relevance to them, they are going to be stuck in school for several more years with no way out,  and they cause problems.  So let’s hire a couple of guys to fix the kids! 

Why not fix the schools to make them relevant and engaging?!?   No, that doesn’t seem to be in the plan.  Instead, we’ll identify and target these at-risk kids with a series of behavioral modification techniques (as I would perceive intervention and incentive programs) to try to get them to fit in with the way school is done.

To think about… 

• Are the other 80% of the students in school engaged, enthusiastic learners?  Or are a great majority simply “doing their time” with the hopes of being released when their sentences are up (i.e. finish 12th grade)?
• Are students that are strongly engaged (at least trying to get good grades and not causing trouble) well served by the schools as they are?
• How many of the classes that your child(ren) are in (or have been in) have caught their imagination, engaged them to learn (not just get a good grade), and have motivated them to work their hearts out for the love of the subject?  In my case, there have only been a very few - but it it’s great to see my children motivated in this way.  What would school be like if only 2 - 3 classes each semester reached this level of engagement?  I’m afraid the school atmosphere would be so disrupted that somebody would put a stop to it!   

Alfie Kohn has a couple of good articles on this subject, “Constant Frustration and Occasional Violence: The Legacy of American High Schools” and “Choices for Children: Why and How to Let Students Decide”.  I recommend them both if you want to think further about these issues.  Gary Stager’s article about working with kids in the Main Youth Center (juvenile detention center), “Constructive Technology as the Key to Entering the Community of Learners”, is also great (and fits in with my prison metaphor).

After my son, Zach, was diagnosed with type 1 (juvenile) diabetes in 2005, I discovered that I wouldn’t be able to take care of it all at home.  We needed the school personnel responsible for him to know what danger signs to look for - and how to respond to emergencies at school.  I put together an instructional program called Diabetes @ School to help school personnel responsible for him understand type 1 diabetes and the role they could play in helping us keep Zach healthy and happy during the school day.

The program was written in Adobe (previously Macromedia) Authorware.  Authorware allows delivery on both CD-ROM or over the internet.  I always provided the program to school personnel on CD-ROM, but I’ve made it available now on the g4classes Moodle here.  The Main Menu of the program is shown in the screenshot to the right.

I attempted to provide both the information teachers would need along with a personal appeal for them to actually work with us (Zach’s parents).

 The introduction included a video of me describing the week prior to Zach’s diagnosis and a quiz.  Type 1 diabetes is much different than type 2… but people know much more about type 2 since it is much more prevalent.  Unfortunately, I felt knowledge of type 2 would actually interfere with a teacher’s understanding of type 1.  Therefore, the quiz was designed to highlight the differences between the two types and make the teacher score poorly.  I hoped that this would motivate them to work through the rest of the program.

The screenshot to the right is typical of the introduction screen for a section.  I provide a video, a narrated slideshow, or an audio clip designed to highlight the need for the section.  Then a preview of the section is provided. 

 >

 >

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 >

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  Each section consistes of 5 to 7 screens.  The screenshot at right is a typical information screen.  Information and  a multiple choice question are included on each screen.

Most of the questions are factual information from the screen.  A few are application requiring the teacher to really think through what is going on. 

Feedback is provided as soon as one of the answers is selected.

I believe the Diabetes @ School program provides the information that school personnel need to care for Zach during the school day.  I believe that the videos and slideshows help make the instruction personal. 

I do see, however, 3 serious problems with the instruction:

1. I don’t think any of Zach’s teachers actually work through the instruction.  Teachers are very busy (just like the rest of us) and most already know people with type 2 diabetes.  They may not see a need for this instruction.  The quiz in the introduction was supposed to “grease the skids” by helping the teacher understand that what they think they know about diabetes is very likely associated with type 2 diabetes and not applicable to type 1.  However, if they won’t do the introduction, there’s no chance that this can work.
2. The instructional strategy is not very motivational or fun.  The program provides important information, but does not provide for any student (actually, the students are teachers, in this case) control and does not really provide any motivational elements in the actual instruction (I might be able to argue that the intro sequences for some of the sections are motivational). 
3. Authorware delivery on CD-ROM is straightforward.  And installation of the web player over the internet is automatic.  However, some institutions have their networks locked down so tight that normal users may not be able to install the player.  I’m not sure why schools would fall under the “super secure” category, but I know the Christian school that Zach attends has their network locked down pretty tight.  For example, I have a flash based web program we used 1 year for communication of Zach’s blood sugar at lunch.  The teacher’s password wouldn’t even allow for the installation of the flash player!

So, why am I reflecting on all of this here?  As the new school year approaches I’d like to revamp and update the Diabetes @ School program.  In doing so I plan to try to address the 3 problems I’ve discussed above.  I’ll probably discuss the changes in the next few posts on this site.  If you have any suggestions on how to address the problems (or if you’ve looked through the program online and have any comments or suggestions), I’d love to hear them.

I’ve just started reading Alfie Kohn’s book “What does it mean to be well educated?”  I was surprised to find that he answered the question on page 10.  Basing his definition on Dewey’s belief that the “goal of education is more education”, Kohn answered the question…

“To be well educated, then, is to have the desire as well as the means to make sure that learning never ends.”

I’m not qualified to debate this with either Mr. Kohn or Mr. Dewey.  But I do feel qualified to reflect on what this means to me.

• “to have the desire”
  • If a person associates learning with school (seems natural) and consider a continuation of school (as it has been “done to” them) an undesirable thing, he will not be likely to desire learning that never ends.***
  • This “desire” will likely have to be intrinsically motivated - as there are probably few extrinsic rewards for a lifetime of learning (obviously, specific learning objectives like an MBA may be extrinsically rewarded, but I would suggest that examples such as this are few and relatively short in comparison with a lifetime).***
• “as well as the means” implies a number of things
  •  Financial means - one must have skills and knowledge that are marketable.*** 
  • Security means - one must have their immediate needs (safety, food, shelter, medicine, …) met before one can pursue lifelong learning (read about Maslow’s Hierarchy here for more information).
  • Freedom means - one must have the basic freedom to make choices such as pursuing a learning goal.
  • Intellectual means - one must have basic learning skills such as reading, writing, etc ***
  • Intellectual means #2 - it is extremely important that one have the goal setting skills (the ability to lay out a plan for achieving a learning goal) and metacognitive skills (the ability to monitor one’s own learning and make appropriate adjustments to attain their learning goals) to be a successful lifelong learner.*** 

Wow!  Even the best schools can’t achieve all of these criteria.  But schools can certainly have an effect (either positive or negative) on those that are marked with ***.

Are our schools encouraging intrinsic motivation and creating lifelong learners? 

Are our schools helping students acquire the cognitive and metacognitive skills needed to pursue a life of learning? 

Or are our schools killing off the desire and means for one to become a lifelong learner?

One of the complaints I read about school is that it is NOT an authentic preparation for the world of the workplace.  And I’ve always agreed.  When I think about school, I think about…

• Rigid and strict authoritarian hierarchy - with the student at the bottom.
• Rigid time scheduling… Students have little input - they are told when to arrive, when to start class, when to go to the next class, when to eat lunch, when to leave, when to go to the bathroom!
• Rigid control of methods… Students have little say in what they learn, how they learn it, or how they demonstrate their learning.
• Overdependence on extrinsic rewards and punishments.
• Numerous arbitrary (and sometimes senseless) rules and assignments… no student buy-in required.   

The world of school seems totally foreign to my work life… and, of course, I consider my life to be authentic.

Then, out of the blue, it hit me.  The characteristics of school that I mentioned above ARE a completely authentic preparation for the job market - at least if you only consider the lowest-paid, lowest-skilled, and least desirable jobs our economy has to offer!

Note: I just finished reading the second essay in Alfie Kohn’s book “What Does It Mean To Be Well Educated?” titled “Turning Learning Into A Business”.  I’ve read this essay before and it is clear that the “blue” that my ideas spawned from may well have included Kohn’s writings. 

In my last post, I discussed a project that I feel would be appropriate for upper elementary students.  I noted, however, that I thought it (the car driving simulation) would probably appeal much more to boys than girls.  In this second post about Scratch as a constructive learning environment for upper elementary students, I’ve selected a project that I thought may appeal more to girls - a virtual pet simulation.

A screenshot of the project is shown to the right.  Run the project here.  Download the project file here.  As it is now, the project is not very interactive.  All you have to do is click on the egg and make sure the food doesn’t run out.

So what can an upper elementary student learn from making such a project?

• Scratch programming constructs and modular programming.  The project uses loops, conditionals, broadcasts, and sprite / edge detection.  
• Debugging and troubleshooting techniques. 
• And hopefully she will have some fun!

One of the things I like best about the project is that there are so many ways to enhance and improve it.  A student could choose to:

• make the project with any kind of pet - either from the wide array of art provided with Scrath or by drawing his own.
• If he wanted the butterfly, he could have it metamorph from a caterpillar instead of hatch from an egg - luckily, we’re not talking science here
• Keep track of the pet’s age.
• Add variables to keep track of the pet’s happiness and provide a way for the user to play with the pet to increase its happiness.
• Add the capacity for the pet to “poop” and provide an interesting way for the user to clean up after it.
• Allow the pet to start smaller and grow to full size as it ages / eats.
• Make a cage on the screen for their pet to live in.  When they are finished playing, allow the pet to escape by opening the pen and allowing the pet to find his way out and return to the wild.
• Fix the bugs in the program… where the butterfly gets caught along an edge for a while occasionally.

Would an upper elementary student find such a project engaging?  Any comments? 

On reflection, the motion in this project may make it a little too advanced for an upper elementary student.  If a student chose to attempt a project such as this, it might be better to encourage her to do it without the motion at first.  As a second step she could add very simple motion… glide to the food when the pet gets hungry.  Finally, she could add some sort of randomness to the motion.

I’ve been investigating the use of Scratch as a constructive environment for students to demonstrate their understanding of various concepts in the classroom.  In this post I’ll be making a bit of a stretch… Can students use Scratch in a constructive way to help them learn a foreign language?

So what do you do in a foreign language class?  It’s been a lot of years for me… but if I remember correctly;

• learn vocabulary and conjugation
• practice listening, speaking, reading, and writing in the language to be learned

It appears to me that one of the deficiencies in learning a foreign language in the classroom is a lack of context - a real-world situation in which to use and practice the language being learned.  I began wondering if students could use Scratch to construct simple contexts for practicing listening and reading a foreign language.  To investigate this question, I constructed a simple Scratch program to provide a context for listening and reading in a foreign language.

The assignment would be something like…

• Create a Scratch project that creates a context for the use of this week’s vocabulary words.  Use the words in phrases that make sense within the context.  Phrases should be both visible and oral.
• This could be done individually, but I think it might be more appropriate to do the exercise in small groups of 3 or 4 students.
• Students could use all the projects to practice their vocabulary words - hopefully in a realistic context (as opposed to flashcards).

The stage of the project is shown to the right.  Once the program is running (by clicking the green flag above the stage in the web browser), the student simply clicks the “Say Something!” button.  A text box appears and the student hears the short phrase in Spanish.

The student(s) creating the project get the opportunity to use the vocabulary words in a real-world context, in contextually correct phrases, and pronunciation.

Students viewing the different projects get to see and hear the vocabulary words used in a number of (hopefully) disparate contexts.

Run the project by clicking here.  The project file is available here.

This is a very simple project.  I believe a 4th or 5th grader (9 or 10 years old) familiar with Scratch could easily create such a project.

Could a constructive use of Scratch in building such projects in the context of a foreign language classroom improve student learning?  Would students be engaged by such activities?  Could such projects allow the teacher to better diagnose student learning problems?  What would be the roadblocks to such projects in the foreign language classroom?

 P.S. My 15 year old daughter in Spanish 2 has informed me that my translations and pronunciation are pretty bad.  She was particulary amused with the question about coming to play on top of my house.  “Real” students should be able to do much better!

While I’m still a big advocate of Scratch as a constructive environment for children to learn programming along with powerful ideas in mathematics and science, I have run across several limitations.

Limitations are common in engineering.  Limitations - often referred to as trade-offs - are a part of every project.  I had one coworker (Electrical Engineer) who used to say - “I can do it fast, good, cheap; pick 2 out of 3.” 

In a classroom situation using Scratch to demonstrate a concept, I suspect students will run across these limitations occasionally.  Usually, all that is needed is a creative trade-off.  I can’t figure out how to make _____, but this other idea I can do is pretty good.

In my efforts to think through ways in which Scratch could be used by kids in a classroom situation to demonstrate their knowledge of a scientific concept, I started thinking about Radiocarbon dating (OK, so I have odd thought patterns!).  Suppose the class has 20 - 25 kids and 5 computers.  What could a teacher do to make a constructive use of Scratch to help kids understand Radiocarbon dating.  The following came to mind.

• Break kids into 5 small groups.
• Break out the basic concepts of Radiocarbon dating… I break them down as
  • How is Carbon 14 created?
  • How does Carbon 14 break down?
  • What is half-life?
  • How does the concentration of Carbon 14 change over time?
  • How does Radiocarbon dating work?
• Allow the groups to choose one of the questions to study.  Each group studies their question (with the teacher acting as a collaborator / consultant as needed) and creates a Scratch project to demonstrate the concept.
• The groups present their projects to the class and answers questions from the rest of the class.

I think such projects could let the kids assume multiple roles; researcher, designer, programmer, teacher, and mathematician (at least in 1 or 2 of the projects).  Do you think the students’ understanding of Radiocarbon dating would be enhanced by such an assignment?

OK, back to limitations.  The most mathematically complex of the questions has to do with the concentration of Carbon 14 over time, so I started thinking about how one might construct a Scratch project to demonstrate his knowledge of this concept (and teach the other classmembers).  Several ideas came to mind - and met with the limitations of Scratch.  Ideas and limitations included:

• Given a starting number of Carbon 14 atoms, calculate the number of C-14 atoms at times in the distant future.  But Scratch has limited math capabilities.  The concentration decreases as an exponential function.  Scratch has no provision for trig, logarithmic, or exponential functions. 
  Trade-off?  Increase time by half-lifes and hard code in the number of C-14 atoms at each time.
• Somehow graphically represent the  number of C-14 atoms remaining.  Well, we could draw a sprite for each C-14 atom and have them disappear or change colors as time increases.  But Radiocarbon dating is good to about 60,000 years or 11 half-lifes.  To have even 1 C-14 atom left after 11 half-lifes, we have to start with 2048 sprites.  But Scratch has limited sprite capabilities.  To manually create and place the 2048 sprites would be a tremendous amount of work. 
  Trade-off?  Maybe draw a graph of the number of atoms over time manually and have a pointer sprite move along the curve as time changes to illustrate the passage of time.  (I used Excel to do the calculations and draw the curve).

 My project looks like the picture to the right.  This project does illustrate the concept pretty good.

• Students can see that the number of C-14 atoms drops off over time.
• The concept of half-life can be explained from the project.
• Students can see why radiocarbon dating wouldn’t be good for really long periods of time (sensitivity of detection / measuring equipment becomes extremely critical).

Run the project here.  Download the project file here.

The biggest problem I have with the project is the graph… for several reasons:

• Students probably don’t learn about exponential curves until their upper High School years (anyway, my Sophomore daughter in Algebra II hasn’t yet encountered them in any meaningful way).  It’s also not clear at what age a student would have sufficient experience with both the math (exponential functions) and Excel (creating data sets and charts) to be able to create the graph.
•  Given the curve, a 6th or 7th grade student (11-12 years old) could probably create the project.  However, I doubt that the graph (with C-14 atoms / 10’s of thousands of years) will really convey the information to a student of this age.  Some sort of interaction allowing them to change the half-life or time scale interactively may be better - but beyond Scratch’s capability.
• It is likely possible to let Scratch draw the graph as a series of lines (a sprite moving between points with its pen down) at half-life intervals.  Then the student could play with several variables (starting C-14 atoms, half-life, total time, …) and get a better feel for the concept.  In my experience with other development environments, this isn’t so hard to do for a particular data set.  But if one wants to be able to change things to see what happens, one must implement some sort of auto-scaling - which would likely make the project too complex for students younger than high school.

So what can I conclude???  Scratch is a powerful environment for constructive learning.  However, it has limitations, some of which I’ve mentioned above.  As project complexity increases and knocks on the door of Scratch’s limitations, one needs to design clever trade-offs or consider moving to a constructive environment with more capability (such as NetLogo, MicroWorlds, and probably Squeak).  As always, I’d certainly appreciate any comments and suggestions.

P.S. Another limitation is that Scratch does not allow for string variables - nor does it support the methods normally available in Logo to manipulate string variables.