A series of free Science Lessons for 7th Grade and 8th Grade, KS3 and Checkpoint Science in preparation for GCSE and IGCSE Science.
Chemistry in Everyday Life
Importance of Chemistry in Life, Everyday Uses
Our bodies are made of chemicals. When we eat, breathe, or just sit down, chemical reactions are taking place. In fact all matter is made from some kind of chemicals so chemistry is the study of everything.
Dust Explosion Using Corn Starch
There two common types of hand warmers: single-use and reusable. The single-use, disposable version typically releases heat for 1 to 10 hours. Inside the package there is a combination of ingredients (cellulose, iron, water, activated carbon, vermiculite and salt). When these ingredients are mixed together and exposed to air, it begins a chemical reaction called oxidation that releases energy as heat. This heat will last as long as the materials inside continue reacting.
This reusable type heats up when the supersaturated solution within it begins to crystallize. A supersaturated solution is a solution that has been forced to dissolve more solids. This supersaturated solution is very unstable and can crystallize (turn into a solid) very easily. When the flexible metal activator is bent, a few tiny pieces of metal break off. These tiny pieces act as a place for crystals to start growing (often called a nesting site). Once the process of crystallization begins, it won’t stop until all of the solution has turned solid. During this process, a large amount of heat is released; up to 50°C for about 30-40 minutes. To reuse the warmer, it just needs to be reheated in boiling water for a few minutes. The sodium acetate re-dissolves and turns back into a gel-like liquid.
Iron, Rusting and Prevention
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