COFFEE FILTER CHROMATOGRAPHY

Chromatography is one method of investigating the different components (ingredients) that make up a solution. In this case, the ingredients are different ink colors and the solution is black marker ink.

What you need:

  • black non-permanent markers/ felt pens (try a few different brands, only some will work)
  • coffee filter
  • scissors
  • small glass or bowl
  • water

Directions:

  1. Cut your coffee filter into strips (try to make them about 1 inch thick).
  2. Draw a horizontal line onto the middle of the strips with each marker (one line/marker per strip). Try to note which markers you use on each strip!
  3. Fill your glass/bowl with a small amount of water.
  4. Put your strips into the water, so that just the bottoms are touching the water—you want your line to be above the water.
  5. The coffee filter strips will slowly suck the water up to and past the lines, and it will take parts of the ink with it.  The lighter components of the ink will be drawn up more quickly (and rise higher). The heavier parts of the ink will stay where they are.
  6. Remove your strips from the water and let them dry.
  7. Observe how the different markers make different patterns.

LEAK-PROOF BAG

 What you need:

  • Zip-top bag
  • Water
  • Sharp pencils

 Directions:

  1. Fill the zip-top bag about halfway with water and close the zip so that the bag is sealed.
  2. Hold the bag over the sink and poke a pencil straight through both sides (but leave it so that at least an inch of pencil sticks out on either side.
  3. Keep adding pencils for as long as you like.
  4. The bag will not leak.
  5. When you’re done, remove the pencils over the sink.

 The Science Behind the Experiment (from Naked Science by Steve Spangler) Plastic bags are made out of polymers, chains of molecules that are flexible and give the bag its stretchiness. When the sharp pencil pokes through the bag, the stretchy plastic hugs around the pencil, creating a watertight seal around the pencil…and the bag doesn’t leak.

TWO POINT DISCRIMINATION TEST

Different areas of your skin are more sensitive than others. Your fingertips are highly sensitive, while the skin on your thighs is less so. The reason for this is that more sensitive skin contains more special cells that can sense pressure. Try it out for yourself!

 What you need:

  • A paperclip
  • A pen and paper
  • A ruler
  • A friend

Directions:

  1. Straighten out the paperclip and bend it into a U shape.
  2. Have your friend close their eyes.
  3. Arrange the ends of your U paperclip so that they are about 1 cm apart.
  4. Touch both ends gently (and simultaneously) onto your friend’s forearm.  Does he/she feel like there are two separate points touching his/her arm or just one?
  5. If he/she only feels one point, separate the ends of your U a bit farther apart; if he/she feels two points, try bringing the ends closer together. Gently touch them again.
  6. Write down the different distances that you try. The closer the ends of the paperclip are together when your friend can still tell that there are two points, the more highly sensitive the skin in that area is.
  7. Now try the same thing on different parts of the body- palm, fingertips, upper arm, legs, back of the hand, neck, back, nose, bottoms and tops of your feet.

Which body part did you discover has the most sensitivity? The least? Why do you think this is?

Below are some typical distances that you might find:

Fingers | 2-3mm
Upper lip | 4-5mm
Cheek | 6mm
Nose | 7mm
Palm | 10mm
Forehead | 35mm
Foot | 20mm
Belly | 30mm
Forearm | 35mm
Upper arm | 39mm
Shoulder | 41mm
Thigh | 42mm
Calf | 45mm

MAKE YOUR OWN INVISIBLE INK

Try out your skills as a spy by writing secret messages to your friends in your own home-made invisible ink!

What you need:

  • A lemon
  • Water
  • Spoon
  • Bowl
  • Cotton swab
  • White paper
  • Lamp or light bulb

Directions:

  1. Squeeze the lemon juice out into the bowl and add about a teaspoon of water. Stir.
  2. Dip the cotton swab into the mixture and use it to write a message onto the paper.
  3. Wait for the juice to dry- you shouldn’t be able to see any writing on the page.
  4. When you want to reveal your message, hold your paper up to a light bulb or other heat source. Your message should magically appear!

SUGAR CRYSTALS

Also known as rock candy! These crystals are relatively easy to grow (and they’re delicious too!)

 What you need:

  • 1 cup water
  • 3 cups granulated
  • clean glass jar
  • pencil, stick, or butter knife
  • string or yarn (don’t use nylon string)
  • sauce pan
  • spoon
  • (optional) food coloring

 Directions:

  1. Tie the string to your pencil. The string should hang into the middle of the jar without touching the bottom or sides. Get the string damp and roll it in some dry sugar to coat it (this allows the crystals to attach and grow better).
  2. Boil the water in your sauce pan. Ask an adult to help you while using the stove!
  3. Stir in the sugar one spoonful at a time. You lots of sugar in the solution, but not so much that it doesn’t all dissolve. If there is some undissolved sugar, the crystals may start growing onto those instead of the string!
  4. Add a few drops of food coloring if you want your candy to be colored.
  5. Carefully pour the solution from the pan into your clean glass jar. Make sure it’s clean—if there are any leftover food or dirt particles inside, the crystals may grow here rather than the string.
  6. Balance the pencil or butter knife (with the string tied to it) on the mouth of the jar and let the string hang into the solution.
  7. Place your jar in a place where it won’t get disturbed.
  8. Check on your sugar crystals after a few hours and/or the next day to see how they’re growing.
  9. You can let the sugar crystals continue to grow as long as you like. When you feel they are large enough (or if they stop growing), take them out, dry them off, and enjoy!

EGG IN A BOTTLE

 What you need:

  • Peeled hardboiled eggs
  • Bottle with a mouth that is somewhat smaller than the circumference of the egg.
  • Matches
  • Paper
  • Scissors
  • Birthday candles

 Directions:

  1. Cut your paper into long strips.
  2. Carefully use a match to light the paper at one end and quickly drop it into the bottle.
  3. Immediately (while the paper is still burning), set your hardboiled egg on the mouth of the bottle.
  4. The egg will start too slowly-- and then more quickly-- squish itself through the mouth of the bottle and drop to the bottom.  The paper will extinguish itself as this occurs.

 Try it upside down!

  1. Push a birthday candle (or two) into your hard boiled egg.
  2. Light the candle(s).
  3. Place your bottle over the egg so that the candles are inside, but hold it so that air can still get in for a few seconds.
  4. After about 5 seconds, push the bottle down gently so that it is closed off by the egg.
  5. Your egg should squeeze itself up into your bottle as the candles go out.