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By: Jess, Shannon, and Julie :D Chemical Reactants Question: What are some signs that a chemical reaction is taking place? Hypothesis: I think that there will be bubbles, a change in color, and an odor to signify a chemical reaction. Independent Variable: The independent variable is the combination of all the particles in the test tube. Dependent Variable: The dependent variable is the signs of a chemical reaction. Constants: The constants were the amount of the liquids and the amount of substance used.

Chemical Substances



Results from the Lab:



These lab items include- a graduated cylinder, lab glasses, a test tube rack and test tubes, a flask filled with bromothymol blue, a beaker filled with sodium bicarbonate, a container filled with calcium chloride, a triple beam balance, and weighing paper.

Lab Summary- When we mixed 2 solids together (calcium chloride and sodium bicarboate), nothing happened. When we mixed 2 liquids together (bromothymol blue and water), nothing happened. Only when we mixed the right combination of solids and liquids did a chemical reaction occur. Bromothymol blue underwent a color change and turned yellow when mixed with sodium bicarbonate and calcium chloride. This was a sign that a chemical reaction occurred. Also, when we mixed together calcium chloride and sodium bicarbonate with water, it fizzed and bubbled, which is a sign that a chemical reaction had occurred. Also, the bubbles and fizzing is a sign that a gas had formed, which is another sign that a chemical reaction occurred. Last, when we mixed the two solids with water, a precipitate formed, which means that a solid that wasn’t calcium chloride or sodium bicarbonate formed. The chemical formula for calcium chloride is CaCl2 + 2NaHCO3 ---> CaCO3 + 2NaCl + H2O + CO2. We found that the gas that had formed during this reaction was carbon dioxide.

Conclusion- Only when we mixed together the right combination of chemicals did a chemical reaction occur. Signs of a chemical reaction that we saw were a precipitate being formed, a color change, a new odor, and the formation of gas and bubbles. Chemical changes can be many different things, but they all change one substance and make it into another substance.

Question: How does the mass of the reactants compare to the mass of the products in a chemical reaction when a precipiate forms? Hypothesis: The mass will stay the same. Independent Variable: The mass of the reactants. Dependent Variable: The mass of the products. Constants: The glassware and the amount of each substance

Chemicals and Background Information:





Results:

Lab Summary: In this lab we mixed two different liquids, from two different test tubes into one test tube. When we mixed them into one test tube there was a chemical reaction. We could tell there was a chemical reaction because there was a change in color, bubbles, and a precipitate formed. After we mixed the two chemicals and the reaction was over, we poured the liquid into a filter and there was a yellow residue left in the filter and a clear liquid was a the bottom of the test tube. This yellow resiude left in the filter was the precipiate that was formed between the chemicals. Since the mass was the same before and after the reaction, you can tell that the mass of the products compared to the mass of the products does not change. Conclusion: The mass of the reactants did not change during this lab. This means that, even when a precipitate is formed, the mass of the reactants to the mass of the products did not change.