未知物質同定チャレンジ

物理的・化学的性質を使って謎の粉末を同定する

Qualitative Analysis Intermediate (High School) 75 分 ~$10.00

目的

複数の定性試験を適用して未知の白色粉末を同定し、系統的な分析思考能力を養う。

背景

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.

安全上の警告

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

必要なPPE

goggles gloves lab_coat

材料

  • 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

器具

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

手順

1

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

10 分
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 分
3

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

5 分
4

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

10 分
5

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

5 分
6

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

15 分 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 分 Use tongs to handle hot dish
8

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

10 分

予想される結果

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.

後片付け

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

詳細

カテゴリ
Qualitative Analysis
難易度
Intermediate (High School)
所要時間
75 分
推定費用
$10.00
ステップ数
8
材料
6

その他の実験

pH指示薬の虹 45 min ハロゲンのバイルシュタイン試験 25 min 植物色素のクロマトグラフィー 60 min 沈殿による陽イオンの同定 90 min 炎発光分光分析 60 min 炭水化物のデンプン-ヨウ素テスト 30 min 石けん液による硬水試験 40 min 金属イオンのホウ砂ビーズ試験 45 min 陰イオン同定試験 60 min

Frequently Asked Questions

What is the objective of 未知物質同定チャレンジ?
複数の定性試験を適用して未知の白色粉末を同定し、系統的な分析思考能力を養う。
How difficult is 未知物質同定チャレンジ?
This experiment is rated as Intermediate (High School). It takes approximately 75 minutes to complete.
What safety precautions are needed for 未知物質同定チャレンジ?
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 未知物質同定チャレンジ?
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 未知物質同定チャレンジ?
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.