I hypothesize that a chemical reaction has occurred when there is a change in temperature, color. But also when there are bubbles and the evolution of gas. Materials: The materials that were used were Aluminum wire(12 cm), beaker (100 mL), hot plate, copper(II) nitrate (1. 0 M), glass stirring rod, gloves, HCl (1. 0 M), lab apron , lab marker, NaOH (1. 0 M), ruler, safety goggles, test tube (13 mm x 100mm) and test tube rack. Procedure: Safety goggles, gloves, and lab apron were put on. (Only the ones who were doing the experiment) 50mL of water was placed in the 100mL beaker and heated until boiled.
And the boiled water will be used as the water bath. The lab marker was used to make 3 marks (1 cm apart).
1. 0 M copper (II) nitrate was added to the first mark on the test tube. 1. 0 M sodium hydroxide (NaOH) was added up to the second mark on the test tube. The solutions were mixed with the stirring rod. The test tube was put into the water bath. The burner was turned off and the test tube was cooled. 1. 0 M hydrochloric acid (HCl) was added to the third mark on the test tube and was mixed. The 12 cm piece of aluminum was placed in the test tube. The wire was removed from the test tube. Lab station and equipment were cleaned.
Observations: I observed that color change occurred and turned blue when Copper (II) nitrate and sodium hydroxide were stirred. Also precipitate was formed. When the test tube was placed in the water bath color change occurred again and turned black. Also there was a temperature change occurred, then the 2 substances on the test tube separated and the leftovers dissolved. When the aluminum wire was placed in the test tube bubbles were produced. Within 5 min. copper atoms formed and were the same color as copper but different shape. Analysis: Some causes of chemical changes are combining chemicals and adding energy.
Abstract- In the flame test lab, the flame test was performed to excite the electrons in the samples and ... burner, beaker with deionized water, wooden splints soaked in water, sodium chloride (NaCl), strontium nitrate (Sr(NO3)2), copper chloride (CuCl2), lithium chloride ... placed in the flame, did in fact, change the color of the flame. In lab, two errors were possibly made. The first ...
Two ways that energy is involved in chemical change is when you touch the bottom of the beaker to check the temperature. That involves chemical change. Also when we put the aluminum wire; energy was involved to produce the bubbles. Elements that were used or produced were Al, Cu, H2 and the compounds were Cu (NO3)2, NaOH, Cu (OH) 2, CuO, HCl, CuCl2, and AlCl3. Aluminum chloride is in the solution and you can recover it by evaporating the water. The color of solutions of copper compounds is copper color. Soluble: Copper (II) nitrate, sodium hydroxide, hydrogen chloride, copper (II) chloride, aluminum chloride.
Insoluble: copper (II) hydroxide, copper (II) oxide, copper metal, aluminum metal. A) sodium nitrate+ copper (II) hydroxide B) copper (II) + water C) copper (II) chloride + water D) copper + aluminum chloride E) hydrogen + aluminum chloride Conclusion: The 4 type of observations that indicate when a chemical change has occurred is formation of a precipitate, color change, formation of a gas, evolution of energy. The type of reactions that I observed in this experiment could be useful in the recycling of copper because copper metal was used in the preparation of the original copper (II) nitrate solution.
After several conversions copper metal was again recovered. Advantages: pure metal is obtained from a compound, and the reaction is done in one vessel. Disadvantages: the reaction takes time and may be expensive and the waste products of recovery may cause pollution. Further Questions: 1) If you recover aluminum chloride, would there be a color change? 2) Why did the substances produce copper atoms? 3) How do you know if evolution of energy has occurred?
... most common reason they change color is to hide from predators. They change color to match the backround, so ... and eat the dead skin. The skin can change color do to its layered contrasted pigment. If ... rotate independently like gun turrets. The Chameleon can change color in a few seconds. The p. 2 ... When there is no place to hide, it changes colors to help stay hidden from predators. The Chameleon ...