Desafío de Identificación de Sustancias Desconocidas

Uso de propiedades físicas y químicas para identificar polvos misteriosos

Qualitative Analysis Intermediate (High School) 75 min ~$10,00

Objetivo

Aplicar múltiples pruebas cualitativas para identificar polvos blancos desconocidos, desarrollando habilidades de pensamiento analítico sistemático.

Antecedentes

This integrative experiment challenges students to identify unknown white powders from a set of possibilities (NaCl, NaHCO₃, CaCO₃, cornstarch, sugar, baking powder) using a battery of physical and chemical tests. Students must design their own testing sequence, demonstrating understanding of solubility, acid reactivity, flame tests, and indicator tests.

Advertencias de seguridad

  • Do not taste any unknown samples
  • Wear goggles when heating or adding acid to unknowns
  • Some unknowns may react vigorously with acid

EPP requerido

goggles gloves lab_coat

Materiales

  • Unknown powders (3–5 samples) (2 g each)
    Labeled A, B, C, etc.
  • Dilute HCl (1M) (10 mL)
    For acid reactivity test
  • Distilled water (100 mL)
    For solubility test
  • Iodine solution (5 mL)
    Starch test
  • Universal indicator (5 mL)
    pH test
  • Cobalt chloride paper (5 strips)
    Water of crystallization test

Equipamiento

Test tubes (10) Bunsen burner Nichrome wire loop Spatula Magnifying glass Evaporating dish

Procedimiento

1

Observe each unknown's physical appearance under magnifying glass: crystal shape, texture, color. Record observations.

10 min
2

Solubility test: Add 0.5 g of each unknown to 5 mL distilled water. Stir and observe if it dissolves, partially dissolves, or is insoluble.

10 min
3

pH test: Add 2 drops of universal indicator to the dissolved/suspended samples. Record the pH.

5 min
4

Acid reactivity: Add 5 drops of dilute HCl to a small amount of each dry unknown. Record any effervescence (CO₂ evolution).

10 min
5

Iodine test: Add 2 drops of iodine solution to each unknown dissolved in water. Record color change.

5 min
6

Flame test: Using a clean nichrome wire, test each unknown in the Bunsen burner flame.

15 min Keep face away from flame
7

Heat test: Gently heat a small amount of each unknown in an evaporating dish. Observe melting, charring, or gas evolution.

10 min Use tongs to handle hot dish
8

Compile all results and cross-reference to identify each unknown. Write your reasoning.

10 min

Resultados esperados

NaCl: soluble, neutral pH, no acid reaction, yellow flame. NaHCO₃: soluble, basic pH, effervesces with acid. CaCO₃: insoluble, effervesces with acid, orange-red flame. Cornstarch: insoluble, positive iodine test. Sugar: soluble, chars on heating.

Limpieza

Dispose of acid-reacted solutions in waste container. Clean all test tubes and glassware. Return unused unknown samples.

Detalles

Categoría
Qualitative Analysis
Dificultad
Intermediate (High School)
Duración
75 min
Costo estimado
$10,00
Pasos
8
Materiales
6

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Frequently Asked Questions

What is the objective of Desafío de Identificación de Sustancias Desconocidas?
Aplicar múltiples pruebas cualitativas para identificar polvos blancos desconocidos, desarrollando habilidades de pensamiento analítico sistemático.
How difficult is Desafío de Identificación de Sustancias Desconocidas?
This experiment is rated as Intermediate (High School). It takes approximately 75 minutes to complete.
What safety precautions are needed for Desafío de Identificación de Sustancias Desconocidas?
Key safety precautions include: Do not taste any unknown samples; Wear goggles when heating or adding acid to unknowns; Some unknowns may react vigorously with acid.
What materials are needed for Desafío de Identificación de Sustancias Desconocidas?
The main materials required are: Unknown powders (3–5 samples), Dilute HCl (1M), Distilled water, Iodine solution, Universal indicator.
What results should I expect from Desafío de Identificación de Sustancias Desconocidas?
NaCl: soluble, neutral pH, no acid reaction, yellow flame. NaHCO₃: soluble, basic pH, effervesces with acid. CaCO₃: insoluble, effervesces with acid, orange-red flame. Cornstarch: insoluble, positive iodine test. Sugar: soluble, chars on heating.