real science for today's homeschooler

Separating Colors with Chromatography

Separating Colors with Chromatography

What is Chromatography?

Chromatography is the process of separating a mixture into its individual components. The easiest way to show this process to children is by using chromatography to separate inks. Waterproof inks in permanent markers and ball point pens require a chemical solvent, but the ink in washable markers can be separated with water, making for an easy and safe experiment.

Materials:

washable markers, coffee filters, pie pan

Procedure:

1. Flatten a coffee filter so that it can be written on.

2. Using washable markers, put small dots of different colors around the outside of the filter, about ½ to 1 inch from the outside edge. (Smaller dots work best. It is hard for the colors to really separate if there is too much ink on the paper.)

3. Put water in the bottom of the pie pan, using just enough to cover the bottom completely.

4. Arrange the filter so that it is back in its original shape with the pleats all neat, etc.

5 Place the filter upside down into the pie plate so that the outer edges are in the water. (It is very important that the dots be above the surface of the water in the pan. If the dots touch the water, the ink will dissolve into the water and the chromatography won’t work!)

6. Allow the water to creep up through the filter. As the water reaches the dots, the ink will begin to spread out and separate. This will take some time, but eventually the water will reach the top.

7. When the filter is completely wet, carefully remove the filter and allow it to dry.

8. Examine the results to see which colors make up each of the inks tested.

How it works:

The process of using paper chromatography to separate inks is pretty simple. Most colors of inks are actually made of more than one pigment, or color. Each of those pigments has different properties. Some are heavier than others. When a solvent passes through the ink, it picks up the different pigments and begins to carry them along. The lighter the weight of the pigment, the faster and farther it will travel. As each pigment continues to travel at a different speed, they become separated from each other, allowing you to see the individual colors that make up the original ink.

 

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Popsicle Science – Turn a Summer Snack into a Science Lesson!

Popsicle Science - Turn a Summer Snack into a Science Lesson!

Do you make popsicles for your kids during the summer? Involve them in the process and turn it into a science lesson!

Materials:

juice, plastic cup, ruler, waterproof marker, popsicle stick (or plastic spoon), index card

Procedure:

1. Fill a small plastic cup about ½ full of juice. (Cups with the straightest sides work best.)

2. Cut a slit in the middle of an index card and place it over the cup. Insert a Popsicle stick or plastic spoon through the card and into the liquid, holding it upright with the index card.

3. Make a mark on the outside of the plastic cup at the top of the juice.

4. Measure the height from the bottom of the cup to the mark. Record.

5. Place the cup in the freezer and leave undisturbed until frozen.

6. Remove from the freezer and measure the height of the frozen juice. Record.

7. If age appropriate, calculate the change in height and record.

8. Ask the question, “Why is there more juice in the cup when it is frozen?”

How it works:

Juice contains a large amount of water. Water is one of the only substances on earth that expands when it freezes. Most liquids contract as they get colder as the molecules slow down and get closer together. Water does contract as it cools all the way down to 4°C. But between 4°C and 0°C (the freezing point of water), the water molecules actually begin to spread farther and farther apart. Solid water (ice) is less dense than liquid water because the molecules in ice are spread farther apart than in water. That’s why ice floats in water.

 

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