Have you ever wondered how scientists can distinguish countless chemical substances with just a few simple steps? Are they some kind of magical “sorcerers”? 🤫 Actually, identifying unlabeled chemicals is not as mysterious as you might think! 🪄 With just a few key tips, you too can become a “chemical detective”!
Right now, “Học Làm” will reveal to you the simplest and most effective methods for identifying chemical substances.
Part 1: Observation – “See and Know” 🧐
Just like recognizing a familiar face in a crowd, observation is the first step to “diagnosing” chemical substances. Pay attention to the following characteristics:
1.1 State: Solid, Liquid, or Gas?
- Solid: You can easily observe their shape and color. Examples include table salt (white, small grains), sugar (white, crystalline form), etc.
- Liquid: Pay attention to color, viscosity (thick or thin), and volatility (easy to evaporate or not). For example, water is a colorless, transparent liquid, while cooking oil is light yellow and slightly viscous.
- Gas: Difficult to observe with the naked eye, often identified by smell or special phenomena. For example, oxygen gas is colorless, odorless, and causes a glowing splint to burst into flame.
1.2 Color: “A Myriad of Hues” 🌈
Each chemical substance can have a characteristic color. For example:
- CuSO4 solution is blue
- KMnO4 solution is purple
- K2Cr2O7 solution is orange…
However, don’t rush to “judge a book by its cover”! Because many substances can have the same color. For example, both table salt and sugar are white.
1.3 Smell: Be Careful “Don’t Inhale Toxic Fumes”! 👃
Some gases have distinctive smells, such as:
- Cl2 gas has a pungent odor,
- NH3 gas has a pungent, ammonia-like smell…
Caution: Never directly smell chemical substances! Some gases are very toxic and can be hazardous to your health.
Part 2: Using Chemical “Magic Weapons” – Reagents 🧪
Just as doctors need a stethoscope to diagnose illnesses, chemists also need “powerful assistants” called reagents to identify substances.
2.1 Litmus Paper: “Color-Changing Magic” 💜
Litmus paper is a type of paper soaked in ethanol or water solution containing a dye extracted from the roots of Roccella and Dendrographa lichens. It can change color depending on the pH of the solution.
- In acids, litmus paper turns red.
- In bases, litmus paper turns blue.
- In salts and water, litmus paper does not change color.
2.2 AgNO3 Solution: “Hunting” Cl- Ions 🔍
When AgNO3 solution is added to a solution containing Cl- ions, a white precipitate of AgCl will form, which is insoluble in nitric acid.
AgNO3 + Cl- → AgCl↓ + NO3-2.3 BaCl2 Solution: “Exposing” SO4(2-) Ions 🕵️♀️
When BaCl2 solution is added to a solution containing SO4(2-) ions, a white precipitate of BaSO4 will form, which is insoluble in hydrochloric acid.
BaCl2 + SO4(2-) → BaSO4↓ + 2Cl-Part 3: “Fire Tests Gold, Hardship Tests Strength” 🔥
Sometimes, we need a more stringent “judge” than fire to identify substances.
When each metal element burns, it will produce a flame with a characteristic color. For example:
- Na burns with a yellow flame.
- K burns with a violet flame.
- Cu burns with a blue-green flame…
However, this method requires specialized techniques and equipment and is mainly used in laboratories.
Conclusion:
Identifying unlabeled chemical substances is an important part of studying and researching chemistry. By observing, using reagents, and other methods, you can confidently “decode” chemical substances successfully. However, always remember to conduct chemical experiments under the guidance of a teacher or expert, and strictly adhere to laboratory safety regulations.
Do you want to discover more interesting secrets of the chemical world? Join “Học Làm” to learn more about how to create an account on the connected school or how to draw computer diagrams!
