Chemical properties Like the other alkali metals, potassium is very active. It reacts with water violently and gives off hydrogen gas: So much heat is produced in this reaction that the hydrogen gas actually catches fire and may explode.
Concrete, usually Portland cement concrete, is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens over time—most frequently a lime-based cement binder, such as Portland cement, but sometimes with other hydraulic cements, such as a calcium aluminate cement.
Why are there energy changes when a chemical reaction takes place? Do physical state changes involve energy changes? Exothermic energy changes and endothermic energy changes in chemical reactions are described, and exothermic reactions and endothermic reactions are discussed in terms of bond energies - including calculations of energy transfers for GCSE/IGCSE and basic stuff for GCE Advanced ...
Chemical element - Geochemical distribution of the elements: Knowledge of the geochemical distribution of elements involves elucidation of the relative and absolute abundances of the chemical elements in the Earth and in its various parts—the crust, interior, atmosphere, and hydrosphere.
Chemical reaction - Energy considerations: Energy plays a key role in chemical processes. According to the modern view of chemical reactions, bonds between atoms in the reactants must be broken, and the atoms or pieces of molecules are reassembled into products by forming new bonds.