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Seventh Grade Science News
Skip Pendleton
Sunday, January 13, 2019

The seventh graders finished the first quarter with a microscopic study of viruses. They began the second quarter by learning about cell structures and cell processes.  Important processes they studied were osmosis, respiration, and photosynthesis.  They observed osmosis in several ways.  First, the children soaked carrots in salt water and saw how increases in the relative numbers of particles outside of a membrane can lead to the movement of water from within the cell and result in the collapse of the cell structure. 

Following this, the children observed that particles smaller than water easily pass through cell membranes. To do this the kids made models of cell membranes by filling plastic bags with cooked rice.  They immersed these bags into iodine solutions.  The microscopic particles of iodine flowed into the bags and stained the rice dark blue.  

Finally, osmosis was demonstrated in a lively and effective way in the lab called Osmosis in the Egg.  In this experiment an egg visibly gained or lost mass and volume as osmosis occurred when it was immersed in vinegar or corn syrup, respectively.  

The children learned about the complimentary processes of respiration and photosynthesis by putting a water plant in a bromothymol blue solution, a carbon dioxide/oxygen indicator, and observed how the indicator changed color depending on whether respiration or photosynthesis occurred.  

As winter progressed the kids used microscopes to see mitosis in action in plant and animal cells.  They dissected bean seeds to study the embryos within and grew the embryos for a week to see how mitosis causes growth.  By the end of the quarter the children began to study DNA.  They built paper and plastic models of this nucleic acid to help them visualize its structure and method of replication.  The children took tests on the cell and cell processes this quarter as well.