Name Thomas McElroy Date Feb 2 2024 Period 3
Unit 0: Observing a Chemical Reaction Laboratory Experiment
Directions
Read the Introduction below and complete the Pre-Lab Questions before starting the Laboratory Experiment.
Introduction Al (s) + CuCl2 (aq) → AlCl3 (aq) + Cu (s)
Starting Substances New Substances
The science of Chemistry is based upon observations. An observation is a statement based on sensory data. For example, “the liquid is clear and colorless” is an observation. “There is no change” or “nothing happened” is also an observation. Quantitative Observations involve a measurement; for example, “The temperature is 96oC.” Qualitative Observations is a general description that does not involve a measure; for example, “The liquid is hot.” An interpretation is an explanation or opinion about what is observed. It would be an interpretation to say (without testing) that “the clear liquid is H2O.”
A chemical reaction is a chemical change. Reactants, starting substances will break their bonds & rearrange atoms to form new bonds & make new substances called products. Common evidence of a chemical change are: Evolution of heat & light, increase or decrease of temperature, color change, odor change, gas evolution. When a reaction causes an increase in temperature in the surroundings, it is considered an exothermic reaction, whereas if there is a decrease in temperature in the surroundings, the reaction is considered endothermic.
Pre-Lab Questions: Define and give an example of each below.
| Element | Example |
| Compound | Example |
| Mixture | Example |
| Quantitative Observation | Example |
| Qualitative Observation | Example |
| Reactant | |
| Product |
Materials Needed
25-mL Graduated Cylinder 100-mL Beaker Electronic Balance Clamp
Thermometer Stirring Rod Scoopula/spoon Ring Stand
Copper (II) Chloride Crystals/Powder Aluminum Foil Filter Paper/small tray
Safety Precautions:
Copper (II) Chloride is a skin and respiratory irritant. It is highly toxic by ingestion and inhalation.
If contact with skin does occur, notify your teacher and flush the area with plenty of water.
Wear Safety Goggles at ALL TIMES!
NOTE: Record ALL temperature values to the tenths place!
Procedure (if absent use : Absent: Obs A Chm Rxn link to complete the lab)
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Measure 15.0 mL of tap water using your graduated cylinder & pour it into the small beaker. Place it on the Ring Stand so that the Thermometer sits in the water without touching the bottom of the beaker. Record the Initial Temperature to the tenths place & make as many observations (minimum of two) as you can regarding the appearance of the substance & classify it as an element, compound or mixture.
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Take the filter paper/small tray & your scoopula/spoon to the Electronic Balance. Place the filter paper or small tray on the Balance Pan, & then hit the “Tare” or “Zero” button. When the balance reads “0,” use the scoopula/spoon to measure & carefully transfer about 1.50-g of the Copper (II) Chloride onto the filter paper/small tray. Record as many observations (minimum of two) as you can regarding the appearance of the substance & classify it as an element, compound or mixture.
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Add the Copper (II) Chloride to the Small Beaker of tap water & stir with the Stirring Rod. Record the temperature to the tenth’s place & make as many observations as you can (minimum of two) regarding the appearance of the substances in the beaker. Classify the contents of the beaker as an element, compound or mixture.
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Measure & cut a 5 x5 cm2 piece of Aluminum Foil. Record as many observations (minimum of two) as you can regarding its appearance and classify it as an element, compound or mixture.
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Loosely crumple the aluminum into a ball & add to the mixture. Press it down with the Stirring Rod until something begins to “occur or happen” within the Beaker.
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Record as many observations (minimum of two) you can make while the reaction is taking place & record the highest temperature observed during the activity. Classify it as an element, compound or mixture
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When all activity within the beaker has stopped, empty the contents of the container into the designated waste contained (Labeled “Lab Waste”) under the Fume Hood.
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Wash ALL MATERIALS in a soap/water solution, dry ALL MATERIALS, and return ALL MATERIALS to their original location. Wipe your lab station down and throw out all trash into the trash can.
Data Table: Reactants
| System | Observations | Temperature (oC) | Classify as an Element, Compound, or Mixture |
| Step 1: Water | |||
| Step 2: Solid Copper (II) Chloride CuCl2(s) | --------------- | ||
| Step 3: Water & Copper(II) chloride Aka: CuCl2(aq) | |||
| Step 4: Aluminum (Al) | --------------- |
Products
| Step 5: After the Al has been added to the CuCl2(aq) |
Analysis Questions
- What is the difference between an observation and an interpretation?
- List 3 pieces of evidence that a chemical reaction occurred in this activity that you observed.
- Record 2 Physical Properties of solid Copper (II) Chloride that you gathered from your observations in your data table. (Physical properties are characteristics that describe unchanged characteristics of a substance).
- The surroundings in your experiment was where the thermometer was sitting which is in the solution of the beaker. Was the reaction ENDOTHERMIC where the reaction absorbed energy (temperature of surroundings decreased) OR Was the reaction EXOTHERMIC where the reaction released energy (temperature of surroundings increased)? State & Explain your answer.
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List the chemical formulas of the Reactants and Products for the Chemical Reaction in this lab below:
Reactants → Products