or a chemical change in several experimental trials.

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1 Regular Chemistry Lab Chemical and Physical Changes. Intro: As we study matter, we base most of our classification and identification of pure substances on chemical and physical properties. A physical property describes the physical characteristics of a substance and includes such things as color, odor, density, melting point, boiling point, mass, volume, phase, and solubility. When measuring a physical property the identity of the substance does not change. Chemical properties describe how a substance reacts or behaves in the presence of another substance. Rusting or oxidation is an example of a chemical property. Another chemical property is flammability (if it will burn). When measuring a chemical property, the identity of the substance undergoes a change. When observing a chemical properties new substances are created. Not only do substances have chemical and physical properties, but they will undergo chemical and physical changes. When a physical change occurs, the identity of the substance remains the same. Example: When you melt a chunk of ice, you change it from a solid into a liquid. But the substance is still water. In fact you can change it back into its solid state by refreezing the substance. This would be a physical change. All chemical properties involve chemical changes. When a chemical change occurs, the identity of the substance is changed forever. Example: When iron oxidizes it ceases to be iron and becomes a compound (cpd) called iron oxide. Iron oxide has totally different properties from iron. Sometimes a chemical change cannot be observed directly, but there are 4 ways to identity when it is taking place. l. There is a permanent change in color 2. There is a change in temperature 3. A gas is formed (It bubbles and fizzes) 4. A Precipitate (ppt.) is formed. I) Purpose: The purpose of this lab is ID if a substance is undergoing a physical change or a chemical change in several experimental trials. Materials: goggles Magnesium ribbon (Mg) watch glass Sodium chloride (NaCl) eyedropper Distilled Water (H2O) 20 ml test tube Silver Nitrate Solution (AgNO3) 50 ml beaker Hydrochloric Acid (HCl) test tube holder Powdered Sulfur (S) Bunsen Burner Iron Filings (Fe) Magnet Graduated Cylinder Safety: You must wear goggles with this lab at all times. Hydrochloric acid is very corrosive Tie your hair back and do not wear bulky clothing No open toed shoes can be worn. Procedure: Copy the data table before coming to class. When conducting the experiment record your observations by placing an x in the box that corresponds to the changes you observe. If none of the 4 items occurs leave it blank.

2 Experiment 1 l. Add a micro spatula (small scoop about the size of a pea) of sodium chloride to a small quantity of DISTILLED water (about 5-10 mls) in a large 20 ml test tube. Shake the contents of the tube. Does it change color? Does it fizz? Does it get hot or cold? Does it form a ppt? 2. Next add 10 drops of silver nitrate, AgNO 3, to the NaCl-water mixture. Does it change color? Does it fizz? Does it get hot or cold? Does it form a ppt? Experiment 2 l. Obtain a piece of Mg ribbon Mg. Tear these pieces into 2 or 3 smaller pieces. Does it change color? Does it fizz? Does it get hot or cold? Does it form a ppt? 2. Place these into a large 20 ml test tube and add a few drops of concentrated hydrochloric acid, HCl. Does it change color? Does it fizz? Does it get hot or cold? Does it form a ppt? Experiment 3 l. Use a mortar and pestle to grind a few crystals of copper sulfate into a uniform powder. Place a micro spatula of the powder into a small 10 ml test tube. Heat gently over a Bunsen burner for 1-2 minutes. Observe what is happening to the compound. Allow the sample to cool and then add several drops of water to the test tube. Record your observations. Was the color change permanent? Did it get hot on its own? Did is bubble/fizz? Did it form a ppt.? Experiment 4 (May be done as a demo) l. Place the clean watch glass on the electronic gram scale. Press the Tare button to automatically delete the mass of the watch glass. Using a metal spatula, measure out approximately 0.60 grams of iron filings and place into a test tube. Repeat the procedure to weigh out 0.60 grams of powdered sulfur. Place the sulfur into a separate test tube. Test each of the test tubes with a magnet. Are both substances magnetic? 2. Mix the two substances thoroughly into a single test tube. What kind of mixture is formed? Run the magnet along the sides of the test tube. Can the mixture be separates? So has a chemical change taken place? 3. Heat the iron and sulfur mixture with the Bunsen burner for several minutes until the substance glows red hot. CAUTION: DO NOT TOUCH THE BOTTOM OF THE TEST TUBE. Allow the sample to thoroughly cool. Examine the substance by probing it with your spatula or stirring rod. Does it have the same texture as the Fe or S? Does it have the same color as the Fe or S? Next run the magnet up and down the sides of the test tube. Were you able to separate the Fe and S like you did before heating?. Sample Data table (Copy after your purpose) Color Change in temp? Bubbles/Fizzes? Forms a ppt? Type of change? change? Dissolving salt (NaCl) Mixing AgNO3 w/ NaCl Tearing Mg into pieces Adding HCl to Mg Crushing CuSO4 Heating CuSO4 & adding water to it. Mixing Fe and S Heating Fe and S

3 Lab Question 1. How would you define a precipitate? 2. A color change, temperature change, formation of a gas, and the formation of a ppt. are all ways to tell if a substance is undergoing a chemical change. Why would the disappearance of a substance not be a good indication of a chemical change? 3. How can substances in a mixture be separated? (Text book 44-47) 4. When measuring a physical property the identity of the substance (Does or does not) change. 5. When measuring a chemical property the identity of the substance (Does or does not ) change. 6. When a substance undergoes a chemical change. a. the properties of the new substance are like the old substance b. the properties of the new substance are nothing like the old substance. IV)Error Sources-Dont forget to use complete sentences. V)Conclusion. How many chemical and how many physical changes occurred in these laboratory experiments? Changes lab Rubric Prelab completed before class 4 pts Title (upper left) 1 pt Date ( below the title) 1 pt Partners name and

4 period (upper right) All Roman numerals and heading s Data table complete Questions Error Sources listed Conclusion stated 1 pt 5 pts 30 pts possible SCORE Changes lab Rubric Prelab completed before class 4 pts Title (upper left) 1 pt Date ( below the title) 1 pt Partners name and period (upper right) 1 pt All Roman numerals and headings 5 pts Data table complete Questions Error Sources listed Conclusion stated 2 pts 30 pts possible SCORE

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