This week we did four labs to help us understand chemical and physical changes. In the first lab we did, we observed a lighted candle. Before the candle was lit, we looked at the physical properties of the candle. It was white, hard, and spiral. After the candle was lit, we looked at the physical and chemical properties. The physical properties were that the wick on the candle was burned, and the top of the candle was smooth where the wax had melted. The chemical properties were the fire that was burning, and the smoke that the fire created. From this lab I learned that physical properties are easier to determine because you can always see them unlike chemical properties.
In the second lab that we did, we also lit a candle. Fire can't burn without oxygen, so we made a mixture where the gas that came from it was carbon dioxide. The mixture had vinegar and baking soda in it. We then poured the gas over the flame, and the fire went out. I learned from this lab that this reaction was chemical because the gas it what put the fire out. In the third lab we did, we had a small marshmallow, a large marshmallow, and a Bunsen burner. We ripped the small marshmallow in half, (which was a physical change) and then ate it. It tasted sweet, and really sugary. Then we put the large marshmallow on a skewer, and turned the Bunsen burner on. We burned a part of the marshmallow, and then ate it. It didn't taste as sweet as before, and it tasted ashy and gross. When we burned the marshmallow, it was a chemical change because the fire was gas, and it burned the marshmallow. The marshmallow was a solid, because it had a definite shape, and the molecules were packed closely together. I learned from this lab that after we burned the marshmallow, it didn't taste good because the sugar was gone.
The fourth and final lab that we did included sugar cubes, a glass of water, a test tube, and a Bunsen burner. We crushed up two of the sugar cubes, and then put them in the glass of water. We stirred the mixture until the sugar dissolved. At his point, we couldn't see actual grains of sugar, but the water was still a little foggy, so we knew the sugar was still present. I also knew the sugar was still present because when I drank the water, it tasted very sweet. After that, we cut up two sugar cubes, so they could fit in the beaker. After putting on our safety googles, we turned on the Bunsen burner, and put the test tube with the sugar in it ove the flame. The sugar quickly melted, and then turend brown. Then, it turned black and started rising to the top. We removed the test tube from the flame, and then we waited for it to cool. After it was cool, the test tube was broken, and we tasted the substance inside of it. It did not taste sugary, but like the marshmallow, it tasted burnt, and ashy. I learned form this lab that the sugar wasn't there anymore because the substance had melted into carbon. These labs showed me how the physical and chemical changes occur in real life.
Pictures from:
No comments:
Post a Comment