13. Explain the change in a state with one oxample. 14. Conversion of organic matter into biogas is a chemical change. Explain why? 15. Is crystallization a physical change or a chemical change? Why? 16. What is a precipitation reaction? 17. Explain the change in colour with one suitable example, 18. Define oxidation and reduction reaction. 19. What is rusting? 20. Give an example of a Rodox reaction.
Answers
An13. ice change to water , 14. yes , 15. physical change 16. In aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate 17.Rusting 18. the process or result of oxidizing or being oxidized. , Redox is a type of chemical reaction in which the oxidation states of atoms are changed. Redox reactions are characterized by the actual or formal transfer of electrons between chemical species, most often with one species undergoing oxidation while another species undergoes reduction. 19. Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. 20. Examples: nitric acid (HNO3) and hydrogen peroxide (H2O2).
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