Making Observations

Pairs are preferred but you may work alone if you wish. Groups of three or more are not permitted.

The Report

One report per person. Use standard headings for lab reports. Include the data, neatly presented, and the answers to all questions using complete sentences.

The Problem:

When some phenomenon is examined in nature, the process is called making an observation. When the observation is made under artificial conditions, such as by being arranged beforehand by an observer, the process is called an experiment. There are two types of observations: quantitative and qualitative. Quantitative observations involve measurement and are recorded using numbers. “The piece of copper has a mass of 10.0 g” is a quantitative observation. Qualitative observations record characteristics that do not use numbers or which are imprecise. For example “The solution was clear and blue.” and “The chunk of metal was small”. In this lab you will combine chemicals three times and make a series of observations. You will be evaluated on, among other things, the quality of the observations you record in your report.

Reagents and Equipment

1 small square of aluminum foil

1 piece of mossy zinc metal

1 piece of calcium metal

copper(II) chloride solution (100 mL)

phenolphthalein indicator solution (pheno)

2 250-mL beakers

2 large test tubes

thermometer

wooden splint

Data

Record your observations under three headings: “Water, Pheno, and Calcium”, “Water, Pheno, and Zinc”, and “Copper(II) chloride Solution and Aluminium”

Procedure

Zinc and Calcium Metal in Water

  1. Fill two 250 mL beakers 2/3 full of water. Add 5 drops of phenolphthalein indicator solution (pheno) to two test tubes and fill each of them with water.
  1. Invert the test tubes and place one in each beaker without letting any air get in.
  1. Find the masses of one piece of mossy zinc metal and also of one or two pieces of calcium metal. Underneath one test tube, place the piece of mossy zinc, and under the other place the piece(s) of calcium metal. Observe for a maximum of 2 minutes. Record your observations. If nothing seems to happen record ‘no reaction’.
  1. Test any gases collected in step 2 for flammability by attempting to light them with a burning splint.
  1. Clean this up by placing the solid zinc metal in a zinc waste beaker, and dispose of everything else into the sink. Rinse the glassware in the ‘acid rinse’ tank and then rinse again with water.

Aluminum Metal and Copper(II) chloride Solution

  1. Place 100 mL of copper(II) chloride solution into a clean 250 mL beaker and record the temperature.
  1. Take a piece of aluminum foil and roll it into a tube. Place the aluminum foil into the copper (II) chloride solution and observe. Note any temperature change. Record your observations.
  1. After several minutes, decant the solution into the copper(II) chloride waste container. (To decant means to pour out the liquid without pouring out the solid). Put some of the brownish product onto some tissue paper and have a close look. It is not rust, but it is a common substance that is well known to you. Try to guess its identity. Record your observations.
  1. Place the solid waste into the garbage.
Questions

There are a number of important basic definitions in science. Refer to pages 41 and 42 of Hebden, and read the definitions on that page. Answer the following in complete sentences:

Responses written in the form of sentence fragments or point form will not be marked.

  1. Give another term for quantitativeobservation.
  2. Distinguish between qualitativeobservations and quantitativeobservations.
  3. State one qualitative and one quantitative observation you made regarding one of the liquids used in this experiment.
  4. What is the difference between an observation and a description?
  5. Is it possible to prove that a theory is correct? Explain
  6. Why is it important that a theory must be ‘falsifiable’?