Kimya, or chemistry, is the branch of science that studies the composition, structure, properties, and changes of matter. It explores how substances interact with each other and the energy changes that occur during these interactions. Chemists use this knowledge to develop new materials, medicines, and technologies that improve our daily lives. In kimya, there are several key concepts, including atoms, molecules, and reactions. Atoms are the basic building blocks of matter, while molecules are formed when two or more atoms bond together. Reactions occur when substances transform into new products, often involving energy changes, which are essential for understanding processes in fields like biochemistry and environmental science.