Physical and Chemical Changes

In class, we performed four labs that were all very alike. The purpose of these labs were to show examples of physical and chemical changes. A physical change is when the appearance of a substance changes, but the chemical composition does not change. On the other hand, a chemical change is when the chemical composition changes.

The first lab was called “Observing a Candle.” This lab was very simple. We observed a candle before and after it was lit. During this lab, I noticed a physical and a chemical change. After our teacher lit the candle, the candle wax started to melt. Melting is the process in which a solid, in this case the candle, turns into a liquid. This change is a physical change because the appearance of the candle changed. The chemical change that occured in this lab was when the candle started to burn. This would be a chemical change because the chemical composition of the candle changed. The candle caught on fire because of the way the components of the candle reacted with the fire.

The next lab our class performed was called "Pouring a Gas." In this lab, we made carbon dioxide. To do this, we had to mix vinegar and baking soda together. Once the mixture started to fizz, I knew a chemical change occurred. The combining of vinegar and baking soda is a chemical change because the chemical composition of the two components changed. The way the vinegar and baking soda reacted with one another caused a new substance to be formed -- carbon dioxide. Before making the carbon dioxide, our teacher lit a candle. To perform this lab, we had to hold the fizzing carbon dioxide over the candle. When we did this, the fire went out. This because carbon dioxide does not support fire.

The next day, our class did a lab called "Marshmallow Fun." For this lab, we were given small marshmallow and a large marshmallow. After describing the characteristics of both, we took the small marshmallow and ripped it in half. By ripping it in half, we made physical change occur. This would be a physical change because the appearance of the marshmallow changed, but the chemical composition did not change. After ripping it in half, we were allowed to eat it! After we finished using the small marshmallow, we moved on to the large marshmallow. Our teacher lit the Bunsen burner and we put the large marshmallows on on kabob sticks. We roasted the marshmallows over the burner until part of it turned black. The change that occurred in the marshmallows after I burnt it is called a chemical change because the substance changed after interacting with a different substance. Afterwards, we ate the large marshmallow. The burnt part tasted bitter and was hard and brittle. The inside of the marshmallow, however, was soft, creamy, and sweet.

The last lab we performed was a lab with sugar cubes. At the start of the lab, we took a couple sugar cubes and crushed them. This would be a physical change because the substance did not change, just the way it looked changed. Then we took the crushed up sugar and put it in a cup of water. The sugar dissolved immediately. At first, I was confused on whether this is a physical change or a chemical change. I then learned that it was a physical change because a new substance wasn't formed. The form of the sugar changed -- you could still separated the sugar from the water. Then, we put two sugar cubes in a test tube and put it over the Bunsen burner. The sugar went through different stages very fast. It melted, then became caramel, and then burnt all the way through. This would be a chemical change because it describes the way the sugar reacted with the heat. At the end of the lab, I tasted the burnt sugar. It was very bitter and very disgusting.

You can find physical and chemical changes all around you. When it is cold outside and you want to get cozy, you light the fireplace. That would be a chemical change. Another time you see a chemical change occur without even knowing is when you bake. The way the ingredient react with each other creates a whole new substance. In addition, physical changes take place all around you. For example, when comb your hair, you are making a physical change. Your hair is not changing, just the way it looks changes. Furthermore, you create physical changes when you eat. The crushing of the food in your mouth with your teeth is a physical change.

All in all, physical and chemical changes are all around us. You don't just see them in a chemistry lab. I also learned so much more about physical and chemical changes through the labs I completed. I can now tell the difference between the two and give example of both. Additionally, it was intriguing to see physical and chemical changes take place first hand.

Image Sources:

Candle

Marshmallow

Sugar

Separating Mixtures

Procedures:

1. First, remove toothpicks from heterogeneous mixture with your hands.

2. Secondly, remove the marble with the spoon.

3. Take the beans out with the spoon.

4. Then, turn the filter paper into a cone and put it into the funnel. Following this, put the funnel on top of the graduated cylinder. After this, put the beans into the funnel and pour the mixture through the funnel.

5. Once the water goes into the graduated cylinder, take the beans out with your hands and put them aside on the tray.

6. Then, use the magnet to pick up the iron fillings from the funnel. Put the iron fillings onto the tray.

7. After that, dump the sand in the filter onto the tray.

8. Next, remove the funnel from the graduated cylinder.

9. Following this, pour the remaining mixture into the Erlenmeyer flask. Then, turn the hot plate on and put the flask onto the hot plate. This will separate the salt from the water.

10. Once the water is evaporated, you should see the salt. Turn the hot plate off and use the tongs to remove the Erlenmeyer flask from the hot plate. Place the flask onto the table (not the tray!).

11. Lastly, clean up your area.

The seven parts are now separated!

Frog Dissection

Unlike most people, I found looking at a frog's insides quite "cool." Sure, while dissecting the frog I felt bad. I mean, it was a living creature. And yet, I had to take it apart. Before we started to dissect our frog, our teacher told us to get to know the frog. After taking some time to get to know our frog, we decided to name it Kermit (my teacher, "Very Original"). Later one, we discovered our frog was a girl. So we changed its name to Kermita.
The first thing my lab partners and I saw were the blood vessels. When we made the "doors" with the skin in the frog, my lab partner noticed the blood vessels right away. I had a hard time believing her. I always thought that the blood vessels sort of roamed around the body. I was wrong. When my teacher pointed the blood vessels out, I was extremely astonished. The blood vessels were kind of stuck onto the skin. It was almost as if the blood vessels were drawn onto to the skin.
Once we cut through the layers of muscles, we came to the organs. Remember when I said we discovered the frog was a girl, well this is how we knew. When we opened it up, the eggs were the first thing we saw. Because there were millions of them, they took up a huge portion of the frog. The eggs were small and black. To study the organs, we had to scoop out the eggs. This is when I started to feel bad about cutting open a frog. I was surprised that the eggs weren't protected by anything. In the human body, the eggs are in the ovaries and are the size of a cell. On the other hand, the eggs in the frog were visible to the naked eye. Seeing as most organisms exist to reproduce, you would think the reproductive organs and parts would be protected. The next thing we saw was really disgusting. They were these spaghetti shaped things in an orange and yellow color. I'm pretty sure you've already guessed it. They were the fat bodies. Luckily, Kermita wasn't fat, so there wasn't much fat to take out.
After we pulled out the fat, we were able to see the organs. Did you know that a frog has three livers? I didn't. I was flabbergasted when I saw the three livers. At first, I thought it was the lungs and the stomach. I was obviously wrong. The three livers are called the right lobe, the left anterior lobe, and the left posterior lobe. The liver's function is very important. It produces bile, a substance that breaks down the fats in the body. Underneath the livers, wass the gall bladder, the stomach, and the intestines. The function of the gall bladder is to store the bile the liver produces until it is needed. The function of the stomach I would think is quite obvious - it breaks down the food through mechanical and chemical digestion. The chemical digestion is when the hydrochloric acid and pepsin in the stomach break down the food. After the stomach, the food goes into the small intestine. The function of this organ is extremely important. It extracts all of the nutrients in the chyme. The large intestine is not at all like the large intestine in the human body. It looked a lot like the stomach. The large intestine seemed to be the same size as the stomach too. The difference is the function of the large intestine is to prepare wastes for elimination from the body.
We also saw the heart and lungs. The heart pumps the blood. It was white and it actually looked like a legitimate heart. Since it is a major organ, it is protected by the peritoneum (a spider web like membrane that covers the organs). Because there was no air in the lungs, they looked deflated. This is because the frog was preserved.

All in all, dissecting a frog was a fun learning experience. Frogs are interesting creatures and learning how their body works made them even better.

If you are interested in learning more about a frog's anatomy visit the website below:

http://frog.edschool.virginia.edu/Frog2/

My Picture Sources:

http://muppet.wikia.com/wiki/Kermit_the_Frog

http://www.e-tutor.com/et3/lessons/view/52133/print

http://www.scientificillustrator.com/illustration/amphibians/leopard_frog.html

Glogster

This is the link to my glog on the Circulatory System:

http://www.glogster.com/cocoapuffs321/the-circulatory-system/g-6lsvre7un0ips2hu54bo1a0

As the Stomach Churns

Day 1:

In Science class, we did a lab that showed how digestions occurs in the stomach. We used hydrochloric acid dilute, pepsin, water, and cubed egg whites. The hydrochloric acid dilute, pepsin, and water represented the chemicals in our stomach. The egg whites represented the food we are digesting. We had four test tubes that represented four different stomachs. In test tube A, we put the pepsin and three egg whites. Our test tube A had no immediate reaction. Then, we put water, pepsin, and three egg whites in test tube B. Test tube B did not have any immediate reaction other than the water going to the top and the pepsin sinking to the bottom. Next, we put hydrochloric acid dilute and three egg whites in test tube C. This test tube did not have any immediate reaction. Lastly, we put hydrochloric acid dilute, pepsin, and three egg whites in test tube D. This test tube also did not have any immediate reaction. After each test tube, we used litmus paper to test which test tubes were acidic. Test tube A and test tube B were not acidic because the blue litmus paper did not turn pink when it came in contact with the substances inside the test tubes. However, the blue litmus paper turned pink when it came in contact with the substances in test tubes C and D. This is because both of these test tube held hydrochloric acid dilute.

Day 2:

When we came back to science class today, we observed the test tubes again. In test tube A, the egg whites did not dissolve. Instead, the pepsin inside froze and hardened around the egg whites. The next test tube, test tube B, had some change. The pepsin dissolved into the water making it foggy. The egg whites seemed to have shrunk by the smallest amount. In test tube C, there was no reaction. The egg whites did not shrink. When we got to test tube D, we saw a significant change compared to the other test tubes. In our test tube, the egg whites shrunk and the piece were coming off from it. Lastly, we used the blue litmus paper. Again, test tubes A and B did not make the litmus paper turn pink. However, the substances inside test tubes C and D made the blue litmus paper pink. Looking at test tubes A and C, I can confirm that the pepsin and the hydrochloric acid dilute are not powerful by themselves. When they are combined, however, they can do much more. This is shown in test tube D. In this test tube, the hydrochloric acid dilute and the pepsin were combined. In just one day, you could a significant difference from the day before.

Chicken Wing Dissection

In class, we watched our teacher perform a chicken wing dissection. This was to show how the human arm worked. As she was dissecting, the first type of tissue we saw was the skin tissue. The skin is a type of epithelial tissue. This tissue was whitish-yellow and was bumpy. The skin was attached to the muscle tissue. Then, our teacher showed us the muscle tissues. The muscle was pink and smooth. The muscle attached to the bone. Before our teacher reached the bone, she showed us other types of tissue. We saw fat and ligaments. The fat was white and smooth. It is used as a cushion. Next, we saw the ligaments. The ligaments were white. This used to help move the muscle tissue. The fats and ligaments are attached to the muscle tissue. When our teacher reached the bones, we saw the cartilage. This connects to the bones and is used to help the bone move around. Without cartilage, our bodies would be stiff as rocks. The cartilage was also white. In the chicken wing, there are also nerve tissues. However, in the chicken wing our teacher dissected, we were not able to see the nerve. If it was there, it would have been attached to the muscles.

This lab was done to show how a human's arm works. Almost everything is the same. The skin is the first tissue. Then comes the muscle. After that the fats ligaments are shown. Lastly, you will see the bones and cartilage. Additionally, the way a chicken's wing works is similar to the way a human's arm works. In both organisms, the skin is the first layer. It is always used to protect what is on the inside. The muscles move the same too. They both need the ligaments to help. The fat is used to cushion in both organisms. Lastly, the cartilage helps the bones move in both organisms. Although, there are two things that are different. The first one is that the muscle proportions are different in the organisms. The last one is that chickens don't have phalanges (finger bones).

Diffusion Lab

To demonstrate how diffusion works in a cell, we did an experiment with iodine and starch. In the experiment, we put a spoonful of starch and a small amount of water into a plastic baggie. Then, we filled a beaker halfway up with water. Lastly, we poured some iodine into the beaker and placed the starch baggie into the beaker. To finish the experiment, we had to let the baggie sit in the beaker for at least fifteen minutes.

After fifteen minutes, the starch in the bag was supposed to turn purple. This is because of diffusion. Diffusion is the term used to describe the process of molecules moving form an area of high concentration to an area of low concentration. In the lab, the plastic baggie was selectively permeable. Selectively permeable means that only certain things can go in and out. Since the plastic baggie was selectively permeable, the iodine molecules were able to go through the bag and spread into the starch. Once starch and iodine mix, they become purple. This is supposed to happen. However, in our lab the iodine molecules were not small enough to go through the baggie.

This experiment is a demonstration of what happens to cells. The plastic baggie represents the cell membrane. The starch represents the cell and the iodine represents things outside the cell. Our cell membrane is selectively permeable. This way only certain things can go into and out of the cell. For example, the cell allows water to come in and allows waste product to go out. However, it doesn't allow the organelles to go out or waste to come in.

Picture Source:

http://missbzscience.wikispaces.com/4b)+Diffusion+%26+Osmosis