Monday, November 28, 2011

Chemthink; Chemical Reactions

In this section, we learned how chemical reactions take place. At the start, there is the original molecule/reactant that when acted upon, the outcome is a product of a new arrangement of the molecule. Always when a chemical reaction there is a bond being broken, being created, or both are taking place.
When there is a change in chemical structure, there is never a loss or gain of any atoms. So if there is H2+O2 you cannot make a single water molecule, due to the leftover atom. But if there were to be two more hydrogen atoms, there could be two water molecules. This is called the Law of Conservation of Mass. Also, in order to balance a chemical equation, you must change the coefficient in front of the number, so that is matches and a proper reactant/product is created. 

Thursday, November 17, 2011

Combustion Demonstrations

Ms. Leland conducted many three test that all had combustion. The first demonstration was where the took and poured a little bit of ethanol and coated the walls of the bottle with ethanol. Then once the bottle was prepared fully she lit a flame at the end of the bottle and there was a blue flame that entered into the bottle and shot it back. This happened, because all of the ethanol that turned into gas evaporated and shot it back off of the table.

The second test, was she took vinegar and baking soda and put them into a beaker and covered it with her hand, so there was not the reaction where it shoots out but it still reacted. Then she lit two candles and she took the beaker and put it over the candles and they went out. This happened, because the vinegar and baking soda takes a lot of carbon dioxide and candles need oxygen in order to maintain a flame and the candle were instantly put out.

The third test, she filled a beaker with hydrochloric acid and put about two grams of zinc into the beaker. The reaction was instant and the beaker began to bubble, because the zinc began to dissolve and she lit a flame on top of the hydrochloric acid and it caught on fire. This happened, because the hydrogen is VERY flammable and it basically ignited and kept a consistant spiral flame.    

Monday, November 7, 2011

Chemical Reactions and Heat Lab

My hypothesis is, how does the rate of chemical reaction change by the increase of temperature?

Hot water test-20 seconds- 50 degrees C

Room temp. water test- 27 seconds- 25.1 degrees C

Cold water test- 1 minute and 56 seconds- .8 degrees C

                                           This is the chart that shows our results
                                                  of the different water temps.

My hypothesis was correct and the amount of chemical reaction does effect the temperature, because in our test the temperature was changed by the amount of chemicals added to the water test used.

Thursday, November 3, 2011

Freezing and Melting Temperature of Water Lab

In this lab we were testing the temperatures of when we were freezing the water into ice and when the ice was melting into water. My hypothesis is that, if I test the two waters, then the freezing water will be colder  than the melting, because of the ice.

Results and Diagrams:  
                                                  This is the results of the Freezing test

                                               This is the results of the melting part of the lab

                                       This shows how the two graphs compare to one another

                                                    This is when the test tube was frozen

                                             This is the ice after the 5 minute waiting period

                                                     This is the ice as it began to melt

                                             This is the ice as its almost completely melted

As we began to add the salt, the temperature rapidly began to decrease with the ice inside of the beaker. Then after a fifteen minute period, the ice in the test tube had froze, then we left the frozen ice tube out on the table and the temperature increased, but once we put it into the warm water, it melted. These are all shown in the photos above.

1. What happened to the water temperature during freezing? During melting?
The temperature rapidly decreased once we began to freeze the test tube, and the temperature rose slowly as it was set in the warm water.

2. According to your data and graph, what is the freezing temperature of water? The melting temperature? Express your answers to the nearest 0.1°C.
Well the temperature in Celsius when the water freezes is 0 degrees Celsius, and once the temperature is above the 0 degrees point I believe that the ice begins to slowly melt.

3. How does the freezing temperature of water compare to its melting temperature?
The temperature of the water when it was frozen, just stayed right below freezing and maintained about the same temperature throughout the test. The melting temperature was a lot warmer and changed the entire time of the test. 

4. Tell if the kinetic energy of the water in the test tube increases, decreases, or remains the same in each of these time segments during the experiment.
a. when the temperature is changing at the beginning and end of Part I Decreased
 b. when the temperature remains constant in Part I Remains the same 
 c. when the temperature is changing at the beginning and end of Part II Increased
d. when the temperature remains constant in Part II Remains the same

5. In those parts of Question 4 in which there was no kinetic energy change, tell if potential energy increased or decreased.
The potential energy is always increasing no matter what the temperature is.