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Discovering blood


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The other day in 4th grade we decided to inquire on blood.

We all had personal experiences to tell our friends (in English, of course) about our little and not so little accidents related with blood. At the end, we reached the conclusion that blood is a red liquid that is in our body. But… was this all? We were not really convinced, so we decided to investigate to discover more about it and there is nothing better than a hands-on activity.

The first thing we did (well… honestly the teachers did it at home the previous night) was to dye with red food coloring the cereals to make them red. In case you want to repeat the experience use A LOT of red coloring. It will make the activity much more effective.

In class, to simulate plasma, in a glass jar we added water and a drop of yellow food coloring.  Once we discussed about the fact that plasma is the responsible for the fluidity of blood, we added red cereals to simulate red blood cells. Once we did that, the yellow water-plasma suddenly turned red! At this point of our enquiry we discovered that the red blood cells are responsible for the color of our blood. Our jar was getting full, but we were still missing two fundamental elements: white blood cells and platelets.

For white blood cells we chose little white marshmallows and ¡¡¡¡¡added just a few trying to imitate the correct proportion between red and white blood cells. We explained that just like the little marshmallows are sweet and good, also white blood cells are good for us since they protect our body from infections.

The platelets were raisins, darker, harder and smaller than the other two.  These reminded us of how important platelets are to stop hemorrhages.

We really had a good time: it was fun, interesting and we could actually see the same we could have seen observing a drop of blood under a microscope.

Oh, by the way…we also ate more than one marshmallow and some raisins! Stay tuned for our next experiments!

Author: Stefania Franco, Science Teacher Colegio Privado San Luis Gonzaga

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