Dark Stains Evaporation Dried Spill
The science behind coffee rings.
|
|
|
|
|
|
This Week's Experiment - #290 Coffee Rings
Before we hit the road, we always do some housecleaning, so that things will
be neat when we get back home. In cleaning the counters, I noticed a coffee
spill that had dried. It had formed a dark ring, with almost no coffee stain
in the center. This reminded me of an article that I have read on the
science behind coffee rings, giving me the idea for this week's experiment.
You will need:
a light colored counter top
a little bit of coffee or tea
Put a few drops of coffee onto the counter in a place where they will not be
in the way. Wait about half an hour and then look at them carefully. What
do you see? Each drop now has a dark ring around the edge.
Let the drops continue to dry, observing them now and then to see what is
happening. Wait until the drops are completely dry. What do you notice?
The original dark ring is still there and even darker. The area inside the
ring has very little stain. Why?
You probably expected that the entire area would wind up with a fairly even
stain, instead of the ring that you got. Lets think about what happened?
The liquid part of the drop (water) began to evaporate. There was more of
this evaporation at the edges than in the middle. Why? Think about the
shape of the drop. In the center, the surface is flat. At the edge, the
surface curves down to the counter. There is more surface area in the part
of the drop at the edge than in the center. More surface area means more
evaporation. The contact between the drop and the counter gives a place for
the solid parts of the coffee to be deposited. This deposited coffee is what
formed the original ring that you saw.
The ring also gives the liquid coffee a rough spot to stick to. Water is a
very sticky substance, and it tends to cling to many things, including dried
coffee. Because it sticks to this ring, the drop does not get smaller as the
liquid evaporates. Instead of getting smaller, it gets shorter. Since the
drop continues to evaporate faster at the edges, more and more of the coffee
moves there, making the ring darker. At the end there is only a thin film of
coffee left inside the ring, which produces very little stain in the center.
When you finish, be sure to clean the counter. Otherwise, we might both get
into trouble for making a mess.
From Robert Krampf's Science Education Company
PO Box 60982
Jacksonville, FL 32236-0982
904-388-6381
krampf@aol.com
|
|
|
|
Nicholas Academy Index
|
|
Artists, wars, armour, castle games, recipes, geography, quizzes, fashions, pictures of weapons, music, old world maps, women of medieval times, medicine, language, and more.
|
Arabic, German, Japanese, Spanish, French, Italian, Latin, Russian. Games, free software downloads, free online lessons, newspapers, discussion groups, articles, history, culture, quizzes.
|
Play language arts games, improve your vocabulary, create customized puzzles, make your own book! Download free software in the form of shareware, freeware, and demos.
|
Math games, quizzes, fun websites, printable charts, coloring books, tools. Algebra, geometry, fractions, multiplication.
|
Play music games, take free music lessons, explore music theory and history, find great posters.
|
|
Explore animation, filmmaking, build online cities, create and share works of art, write stories, create your own web site, read creativity articles.
|
Science games and quizzes, fun science websites, posters, coloring books, kits, experiments, forensics labs and more.
|
Coloring books, countries of the world, games and quizzes, software downloads, posters, computer jigsaw puzzles, printables.
|
Science can be fun and understandable. Free Experiment of the Week, featuring experiments that are unusual, safe, dramatic, cheap, and fun. From Robert Kramp's Science Education Co.
|
Fun and affordable space items for kids, including toys, games, kits, food products, and more.
|
|
Educational science kits kids will love! Early science kit, DNA explorer kit, robot challenge, forensic lab, volcano kits, crystals.
|
All in one project labs, light kits, sound kits, motion and metal detectors, clap on/off kit, nerve tester and shocker.
|
Civil rights, African American writers, parts of speech, medieval, periodic table of elements, music, astronomy, world maps with flags, literature, poetry, dinosaurs, biology, cats, Japanese anime.
|
Coloring books for kids and adults. Civil war, plants, animals, states, middle ages, cultures, geometric designs, puzzles.
|
Online, via email or through the regular mail. College, accredited high school, free reading and phonics courses, foreign language, history, religion, and more.
|
|
Test your knowledge with these fast, fun, and educational quizzes. Roman numeral addition, world capitals, presidents in order, the elements, world flags, and more.
|
Roman numerals, addition, multiplication, order of statehood, state and world capitals, order of presidents, chemical elements, parts of speech, spanish numbers.
|
Reading systems, loan programs, flashcard, worksheet and test makers, game creators, board games, percentage calculator, puzzle creator, timeline template.
|
SAT, GED, ACT, practice tests, exam preparation. Standardized test practice, content standards listed by state, sample items, scope and sequence, aptitude, essential skills.
|
New and used low cost books and textbooks. Websites with open source books and loan programs.
|
|
Templates, ideas for personal, educational, children's, business sites, design tips and tools, registration and hosting information, step-by-step instructions, quick and easy web page, web building just for kids.
|
Books, posters, videos, software kits, curriculum, courses. Save on teaching supplies, receive free educational materials.
|
This site map lists nearly every page on our site, along with a short description.
|
|
|
|
Educational Poster Store
Hundreds of educational posters in different subject areas. Parts of speech, medieval, solar system, biology, world maps, Einstein, Martin Luther King. Science, math, literature, art, music, english, geography, social studies. If you don't know exactly what you're looking for, this is great to browse for ideas.
|
NASA Website Links
Educational resources include worksheets such as mazes, coloring pages, shuttle model instructions, crossword puzzles, space food tray instructions and grocery list, and more. See the Space Station Sky Watch, view a NASA Astronaut Application or the Space Shuttle Launch Schedule, learn about the U.S. Space Camp and Women in Spaceflight.
|
Zoobooks
Get a free Zoobooks issue and a tiger poster. Zoobooks are the all-in-one, everything-you-wanted-to-know but-didn’t-know-who-to-ask guide to the world’s most fascinating animals, birds, reptiles, and insects. For kids five to twelve.
|
|
