Qualitative and Quantitative Lab

NAME ______MOD _____ DATE ___

Objectives:Distinguish between a physical and chemical change.

Distinguish between observations and inferences.

Classify observations as qualitative or quantitative.

Background: Distinguishing between observation and interpretation is very important in chemistry. An observation is a statement of fact, based on what you detect by your senses. An interpretation is your judgment or opinion about what you have observed. A statement such as “The liquid is clear and colorless” is an observation. It would be an interpretation to say, without further testing that the clear and colorless liquid is water. A qualitative observation is a general description using words while a quantitative observation includes some kind of measurement, usually numbers. “The liquid is hot” is a qualitative observation whereas “the liquid is 95˚ Celsius” is quantitative.

Materials: Scissors, ruler, goggles, aluminum foil (8cm x 8 cm), 150 mL beaker, graduated cylinder, thermometer, stirring rod, plastic spoon, magnifying glass, about ½ tsp. copper(II)chloride dihydrate, water, electronic balance.

Safety: Goggles must be worn at all times. If you check for odors, remember to waft. Copper (II) chloride is an irritant. Avoid skin contact with this chemical. Rinse with water immediately if you get some on your skin. Report any incidents to the teacher. Wash the lab bench after the lab to remove any spills.

Procedure:

  1. Put on goggles. Plug in electronic balance. Put a weighing boat on the balance and zero.
  2. Mass out between 3 – 4 grams of copper(II)chloride dihydrate and keepit on the weighing boat. Carefully remove the boat and chemical from the balance. Using a magnifying glass, observe the chemical and write observations in the data table. Describe the material. Place observations in the correct column.
  3. Measure 15 mL of water in a graduated cylinder and pour into the 150 mL beaker. Carefully add the CuCl2crystals from the weighing boat into the beaker by bending the weighing boat to make a spout. Do not stir. Record observations. How many phases are there?
  4. Use the glass stirring rod to stir the mixture until the crystals are completely dissolved. Record your observations of the solution.
  5. Place the thermometer into the solution and take the temperature. Record.
  6. CAUTION: In the next step, do not observe from above; watch from the side of the beaker. Place a loosely crumpled piece of aluminum foil in the solution, push down with the stirring rod or thermometer and observe for about 5 minutes. Record any change in temperature including the highest temperature.
  7. Record the final temperature after five minutes.
  8. Carefully pour the contents into the waste container designated by your teacher. Do not put any materials down the sink.
  9. Add more water to the beaker and swirl again. Pour into waste container (not in sink).
  10. Wash beaker, stirring rod, and thermometer in the sink. Return the equipment to the proper places.
  11. Clean up lab area of any spills. Return goggles.
  12. Answer lab analysis questions.

System / Qualitative observations / Quantitative observations
Dry copper(II) chloride dehydrate
on white paper
CuCl2 in water (not stirred)
Stirred solution of CuCl2 in water
Temperature of stirred solution
Solution plus aluminum foil
Final temperature of system
  1. When during this lab did a chemical change take place? ______
  1. What clues (observations) led you to believe that a chemical change took place? ______
  1. Identify the five elements inside the test tube (some are in compound form). ______
  1. Make a hypothesis as to what the reddish material could be or where it came from. ______
  1. Differentiate between qualitative and quantitative data. ______