Physical and Chemical Change Objective: Recognize and distinguish between chemical and physical changes. Materials: – lab balance – lab burner – 5 test tubes – test tube rack – test tube holder – watch glass – glass square – microspatula – dropper pipet – mortar and pestle – magnet – insulating pad – safety goggles – lab apron or coat – copper sulfate pentahydrate – iron fillings – sodium chloride – hydrochloric acid – silver nitarate – sulfur Procedure: – magnesium ribbon – paper (5 cm x 10 cm) – birthday candle – matches 1.
Place a small amount of wax from a birthday candle into a test tube. Heat gently ver a burner flame until the wax melts completely; then allow the sample to cool. Next, light the candle, secure it to a glass square, and allow it to burn until it extinguishes itself. Proceed with rest of the experiment while the candle burns. 2. Tear a piece of paper (about 5 cm x 10 cm) into small pieces. Set a watch glass on an insulating square and place the pieces of paper on the glass. Ignite the paper with a match and allow to burn. . Add a microspatula of NaCl (sodium chloride) to a small quantity of water (about 5mL) in a test tube. Shake the contents of the tube. Next, use a dropper to add 10 drops of 0. silver nitrate to the NaCl-water mixture. 4. Obtain a piece of magnesium ribbon about 5 cm long. Tear the ribbon into I-cm pieces. Place two of the pieces into a test tube and a few drops of 6 M HCI (hydrochloric acid). Caution: Use extreme care in handling this acid. It will cause severe burns if allowed to come in contact with the skin.
Touch the bottom of the test tube with your fingertip. 5. Use a mortar and pestle to grind several crystals of CuS04 5H20 into a uniform powder. Place one microspatula of the powder into a test tube. Heat gently over a burner flame for 5 minutes. Allow the sample to cool and then add a few drops of ater. 6. Using a lab balance, measure out the following samples: ). 50 g of iron fillings and 0. 50 g of powdered sulfur. Test each sample with a magnet. Mix the two samples thoroughly in a test tube. Run the magnet along the bottom and sides of the test tube.
Observations and Data: Procedures Description of what Happened Type of change Melting a wax test tube Wax turned to liquid Physical change (melting is a phase change) Melting a candle Melted down to nothing Chemical change (carbon dioxide was produced since candle was burned) Burning paper Turned to ashes Chemical change (carbon dioxide is produced) Mixed NaCl & water. NaCl dissolved in water Physical change (homogenous mixture) AgN03 added to salt water mixture Mixture turned white Physical change (change in color) Water was added to test tube containing HCI Bubbling occurred and test tube heated up.
Chemical; the bubbling meant that there was a production of a new substance which was hydrogen gas) Copper sulfate was heated Turned white Water was added to copper sulfate after it was heated Turned back to blue Physical change (color change) Iron fillings were mixed with sulfur Magnet was used to separate the iron fillings Physical change (mixtures can be separated physically) Iron and sulfur were heated Iron lost its conductivity. Physical change (conductivity is a physical property) When elements combine and form a compound they have different properties then when they exist in their elemental form. Conclusions and Questions 1. . Melting candle wax – physical g. tearing Mg ribbon – physical b. burning a candle – chemical h. adding HCI to Mg – c. tearing a paper – physical i. grinding CuS04 5H20 – physical d. burning paper – chemical J. heating CuS04 5H20 – chemical e. dissolving NaCl – physical mixing Fe and S – physical f. mixing NaCl and AgN03- l. heating a mixture of Fe and S – chemical 2. Two possible indications that a chemical change has taken place are bubbling of a substance and burning of paper. For example, in the experiment when I poured Hydrochloric acid in a test tube and then one magnesium ribbon, the substances started to bubble.
Other than that, when I took the wooden split and lit it, I burned the green paper and it changed brown around the edges of the paper. 3. The “new’ substances that were formed as a result of chemical change were many. When I took the candle and lit it, it burnt and formed smoke. When I took the wooden split and lit the paper on fire, the color around the green paper changed to be brown, urnt and changed into ashes. Also, I poured Hydrochloric acid and magnesium ribbon in a test tube and it started bubbling and it heated up in the bottom. 4.
The following examples do not always indicate chemical change. For example, change in color will always indicate chemical change because the color changes but it does not change the substance’s physical properties. The apparent loss in mass is a phase change; therefore the entire substance goes through a physical change. The apparent disappearance of a substance is a chemical change and will always be a hemical change because it might result of a soluble substance dissolving in a liquid and changes the entire substance in a chemical phase. . Substances in a mixture can be separated depending on the substances involved. You can use a magnet to separate a magnetic substance form a non-magnetic one, filtering, and evaporation. For example, when I put the iron fillings and powdered sulfur into a test tub, I used a magnet to separate the substances. Substances in a compound can be separated by distillation, evaporation, or condensation process because to separate the components will be difficult.