LAB TEST Physical and Chemical Changes

Transcription

1 NAME: DATE: STATION: LAB TEST Physical and Chemical Changes PURPOSE: To observe physical and chemical changes in matter MATERIALS: 3 medium test tubes 1 small test tube test tube rack test tube holder scissors 1 sheet of paper crucible tongs watch glass magnet spatula (5) Bunsen burner sunglasses iron filings (Fe) sodium bicarbonate (NaHCO3) 6M hydrochloric acid (HCl) sucrose (C12H22O11) sodium chloride (NaCl) magnesium ribbon (Mg) sand matches PROCEDURE: Part A 1. Obtain a sheet of paper and cut it into six pieces. Label each with the name of one of the following substances: magnesium, iron, sodium bicarbonate, sodium chloride, sucrose, and sand. 2. Obtain a 1-cm piece of magnesium ribbon from the labeled canister at your station. Place it on the appropriately labeled paper. Using labeled scoops, transfer a small, pea-sized sample of each of the other substances to the remaining papers. 3. Classify each substance as an element, compound, or mixture, and record this information in the data table at the end of this section. 4. Examine each substance carefully. CAUTION: Never taste any of the substances. Record your observations of the physical appearance of each substance in the data table. You must make at least three observations about each substance. 5. Obtain a magnet in a plastic bag. Do not remove the magnet from the bag! Test the effect of a magnet on each substance by passing the magnet under the paper. Record the observations. 6. Combine the samples of iron filings, sodium chloride (salt NaCl), and sand onto a clean piece of white paper. Mix the samples thoroughly. Move a magnet under the paper below the mixture and examine it again. Record your observations: Mixing iron filings, salt, and sand is a (physical / chemical) change. Explain.

2 DATA: SUBSTANCE Element, Compound, or Mixture? Physical Appearance Magnetic? Iron Filings Fe Sodium Bicarbonate NaHCO3 (Baking Soda) Sodium Chloride NaCl (Salt) Sucrose C12H22O11 (Sugar) Sand Magnesium Mg PROCEDURE: Part B 1. Place a watch glass on the laboratory bench close to a Bunsen burner. Light the burner. Obtain a 5-cm piece of magnesium from the labeled canister. Put on sunglasses to protect your eyes! Use crucible tongs to grasp the strip and hold it in the burner flame until the magnesium ignites. CAUTION: Do not look directly at the burning magnesium. Its flame is very bright and can damage your eyes. Do not inhale the fumes. Keep the burning magnesium at arms length at all times, and hold it over the watch glass. Record our observations: Compare the appearance of the combustion product (the material that falls into the watch glass after burning) with that of the original magnesium.

3 Cutting the magnesium is a (physical / chemical) change. Explain. Burning the magnesium is a (physical / chemical) change. Explain. 2. Obtain a 1-cm piece of magnesium from the labeled container and place it into clean, dry medium test tube. Add 10 drops of 6 M hydrochloric acid (HCl) to the test tube. CAUTION: Hydrochloric acid is corrosive to the skin. Feel the bottom of the test tube. Record your observations. Mixing the magnesium with hydrochloric acid is a (physical / chemical) change. Explain. 3. Transfer a small scoop of sodium bicarbonate (baking soda NaHCO3) to two clean, dry medium test tubes. Fill one of the test tubes half full with water. Add 5 drops of 6 M hydrochloric acid to the other. Compare the results: Dissolving sodium bicarbonate in water is a (physical / chemical) change. Explain. Reacting sodium bicarbonate with hydrochloric acid is a (physical / chemical) change. Explain. 4. Add two scoops of sucrose (sugar C12H22O11) to a small test tube. Hold the test tube with a test tube holder and heat it gently in the burner flame. Watch the tube carefully for changes. CAUTION: When heating a test tube, never point the mouth of the tube at yourself or anyone else. Never check for odor from a tube while it is being heated. Remove the test tube from the flame and set it carefully in the test tube rack. Compare the product of the reaction to the original sucrose. Burning sucrose is a (physical / chemical) change. Explain.

4 OPEN-ENDED (FREE) RESPONSE: A mixture of salt, sand, and iron filings is found in the store room. Using evidence from this lab, as well as our discussions in class, how would you separate these substances into three separate containers? Be sure to write a procedure that describes how you would have each of the three substances in separate containers at the end of the lab.

5 NAME: DATE: STATION: PRE-LAB Physical and Chemical Changes Read through the lab and answer the following questions: 1. What six substances are to be tested in this lab? 2. What procedure should you use in this lab when testing a substance to see if it is magnetic? 3. What special precautions should you use when burning magnesium? 4. What property of hydrochloric acid makes its use of particular concern in any laboratory situation? 5. What method should you use when testing the odor of a material? (See your safety rules) When should the odor of materials never be tested? 6. What special precaution should you always use when heating substances in a test tube? 7. What are six indications of a chemical change? (See your notes) a. b. c. d. e. f.

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