docs(notes): update hydrogen peroxide entry

Author: lzwjava

notes/2025-04-12-hydrogen-peroxide-en.md

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-Hydrogen peroxide is a chemical compound with the formula H$$_2$$O$$_2$$. It is a colorless liquid that is slightly more viscous than water and has a slightly sharp odor[1][3]. Hydrogen peroxide is known for its strong oxidizing properties, making it useful as a bleaching agent, antiseptic, and disinfectant[1][4].
+Hydrogen peroxide (H₂O₂) is a colorless liquid chemical compound with a slightly pungent odor. It is a common household chemical and has various industrial and medicinal uses.
 
-### Uses of Hydrogen Peroxide
+**Chemical Properties:**
 
-1. **Bleaching and Disinfecting**: Hydrogen peroxide is widely used for bleaching textiles, wood pulp, and paper. It is also used as a disinfectant for surfaces and in contact lens care[2][3].
+* **Molecular Structure:** It consists of two hydrogen atoms and two oxygen atoms bonded together. The oxygen atoms are linked by a single bond, and each oxygen atom is also bonded to a hydrogen atom.
+* **Oxidizing Agent:** Hydrogen peroxide is a powerful oxidizing agent, meaning it readily donates oxygen atoms to other substances. This property is responsible for many of its uses, such as bleaching and disinfection.
+* **Decomposition:** It is unstable and readily decomposes into water (H₂O) and oxygen gas (O₂) especially in the presence of catalysts like metals, metal ions, or light. This decomposition releases heat.
+* **Acidic Nature:** It is a weak acid.
+* **Solubility:** It is miscible with water, alcohol, and ether.
 
-2. **Cosmetic Applications**: It is used in hair dyes and teeth whitening products. Over-the-counter teeth whitening products typically contain up to 6% hydrogen peroxide, while professional products can contain up to 35%[4].
+**Common Uses:**
 
-3. **Industrial Uses**: Concentrated hydrogen peroxide is used in rocket propulsion and as a component in the production of chemicals and foam rubber[1][3].
+* **Antiseptic:** It is used as a mild antiseptic to clean minor cuts, scrapes, and burns to prevent infection.
+* **Mouthwash:** It can be used as a mouth rinse to help remove mucus and relieve minor mouth irritation.
+* **Teeth Whitening:** It is an active ingredient in many over-the-counter and professional teeth whitening products.
+* **Hair Bleaching/Lightening:** It is used to lighten hair color.
+* **Cleaning and Disinfecting:** It is used as a household cleaner and disinfectant for surfaces, laundry, and even food.
+* **Stain Removal:** It can effectively remove various stains like blood, wine, and grass.
+* **Industrial Uses:** In higher concentrations, it is used as a bleaching agent for textiles and paper pulp, in chemical manufacturing, wastewater treatment, and even as a rocket propellant.
 
-4. **Medical Applications**: At low concentrations (1-5%), hydrogen peroxide is used as an antiseptic for minor cuts and scrapes[4][6].
+**Safety Precautions:**
 
-### Safety Considerations
-
-- **Concentration and Safety**: Solutions above 8% can be corrosive to the skin, and concentrated hydrogen peroxide is highly reactive and potentially explosive when heated[2][4].
-- **Exposure Risks**: Ingestion, inhalation, or contact with concentrated hydrogen peroxide can be harmful, causing irritation and potentially more severe effects[4].
-
-### Natural Occurrence
-
-Hydrogen peroxide occurs naturally in small amounts in the environment, including air, water, and biological systems[3].
-
-Citations:
-[1] https://en.wikipedia.org/wiki/Hydrogen_peroxide
-[2] https://www.britannica.com/science/hydrogen-peroxide
-[3] https://www.gov.uk/government/publications/hydrogen-peroxide-properties-incident-management-and-toxicology/hydrogen-peroxide-general-information
-[4] https://dermnetnz.org/topics/hydrogen-peroxide
-[5] https://ec.europa.eu/health/opinions/en/tooth-whiteners/l-3/1-hydrogen-peroxide.htm
-[6] https://health.clevelandclinic.org/what-is-hydrogen-peroxide-good-for
-[7] https://www.medicalnewstoday.com/articles/hydrogen-peroxide
-[8] https://pubchem.ncbi.nlm.nih.gov/compound/Hydrogen-Peroxide
-[9] https://www.webmd.com/drugs/2/drug-76035/hydrogen-peroxide/details
-[10] https://www.sciencedirect.com/topics/nursing-and-health-professions/hydrogen-peroxide
-
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-Answer from Perplexity: pplx.ai/share
+* Concentrated hydrogen peroxide can be corrosive and cause burns to the skin and eyes.
+* Ingestion of high concentrations can be dangerous.
+* It should be stored in a cool, dark place away from heat and incompatible materials to prevent decomposition.
+* Always follow the instructions and safety guidelines on the product label.