Throughout the week, our class completed a series of labs involving chemical and physical changes. In all labs involving the Bunsen burner, the groups had worn goggles and the girls tied their hair back in order to protect ourselves.
The third lab involved tasting using marshmallows. First, we took a small marshmallow and split it in half, creating a physical change. The marshmallow was white, small, smooth, soft, fluffy, cylindrical shape, and the inside was sticky. After that, we ate the marshmallow. It tasted sweet, sticky, and it had a fluffy texture. After that, we took a large marshmallow and placed it on a skewer over a Bunsen burner. This was a chemical change because we had burnt the marshmallow when placing it over the fire. The marshmallow was brown and black, even more sticky, and in a cylindrical shape. However, the marshmallow tasted chalky, bitter (no longer sweet.) The marshmallow also had a physical change; it was that the marshmallow was melted on the inside. This lab had helped me learn that even when we make s'mores, we're using science as well.
The final lab involved burning sugar. I first concluded that we were going to make caramel. However, we were burning the sugar far beyond caramel. To start off, a sugar cube is small, a cube shape, white in color, sweet in taste, hard, and smooth in texture. We then had to crush the sugar cubes into fine sugar and this allowed us to create a physical change. We then poured the sugar into a cup of water and tasted it. This allowed us to create another physical change because the sugar was still there even though it was not visible. The sugar also still tasted sweet. This observation reminded me of the ocean because the water has salt even though we cannot see it but can taste it. The next process was to put two whole sugar cubes into a test tube and hold it over a Bunsen burner using tongs. Water started to form in the tube because the sugar was melting. Then the sides of the test tube started to turn yellow and the sugar turned into a golden brown color. Then gradually, the sugar turned black. After turning off the Bunsen burner and setting the test tube aside to cool, my group noticed a few physical changes. The sugar was no longer small, but large and the shape of the sugar was in the shape of the test tube. The color had also turned from white to black and it tasted bitter instead of sweet. The sugar was also hard and rough instead of smooth. As you can see the sugar had completely went through a chemical change. The sugar is no longer sugar, but turned into carbon. This lab has definitely showed me the significance of chemical change in such a simple substance as sugar.
As you can see, chemical and physical changes happen everywhere and not only when you intend to, like in a lab. Changes and properties help a person understand the substances in the world better and allow them to understand the reactions that occur with each other as well.
Sources:
http://www.shutterstock.com/pic-62515567/stock-photo-flame-of-a-single-birthday-candle-burning.html
http://ficklekitsch.blogspot.com/2011/05/hair-experiments-baking-soda-and.html
http://www.shutterstock.com/pic-1611432/stock-photo-marshmallow-on-a-stick-being-roasted-over-a-camping-fire.html
http://www.ehow.com/how_8220027_burn-sugar-cube.html
The first lab was one of the simplest. What was done was to observe a candle before and after it was lit. Before it was lit, the physical properties was the color (white), it was waxy, hard, bumpy, and spiral. These properties were determined by using sight and touch. However, there were no chemical properties right now because nothing has happened or changed. Then the candle was lit. When the candle was first lit, the physical changes were that it was melting and the candle looked smooth and shiny. The candle was also getting smaller in size. And the chemical changes were that it was burning and that there was smoke and a flame from the fact that it was lit. From this lab, I learned what combustion is. Combustion is the name given to a process such as burning a candle. I was surprised to find out that I used science every time a candle on a birthday cake is lit. Though this is a simple lab, this would definitely help me when making any science experiments, and I will be able to make hypotheses that will most likely be correct.
The second lab also used a candle, however it involved pouring a gas on to the candle in order to observe the chemical and physical changes. First, we lit the candle and this created both physical and chemical changes as stated above. While the candle was lit, we poured some vinegar inside a beaker and then put a spoonful of baking soda. When the vinegar and the baking soda reacted with each other, creating a gas, we put the beaker right next to the flame. And because a flame lives with carbon dioxide, the gas allowed the flame to automatically turned off; and this followed by a large cloud of white smoke. We then lit the candle again and did the same procedure observing the same reactions again. This lab helped me in learning more about how flames can live and how the can die.
As you can see, chemical and physical changes happen everywhere and not only when you intend to, like in a lab. Changes and properties help a person understand the substances in the world better and allow them to understand the reactions that occur with each other as well.
Sources:
http://www.shutterstock.com/pic-62515567/stock-photo-flame-of-a-single-birthday-candle-burning.html
http://ficklekitsch.blogspot.com/2011/05/hair-experiments-baking-soda-and.html
http://www.shutterstock.com/pic-1611432/stock-photo-marshmallow-on-a-stick-being-roasted-over-a-camping-fire.html
http://www.ehow.com/how_8220027_burn-sugar-cube.html
