science

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Across
  1. 2. a natural process that converts a refined metal into a more chemically stable oxide.
  2. 8. a diatomic anion with chemical formula OH⁻. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge.
  3. 9. any substance that in water solution is slippery to the touch, tastes bitter, changes the colour of indicators (e.g., turns red litmus paper blue), reacts with acids to form salts, and promotes certain chemical reactions (base catalysis)
  4. 12. a chemical process in which a substance reacts rapidly with oxygen and gives off heat.
  5. 15. another word for base
  6. 16. When a reactant loses electrons during a reaction.
  7. 17. a chemical reaction in which acid and a base react with an equivalent quantity of each other.
  8. 18. a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light, electricity, or sound.
  9. 20. a chemical element with the symbol Fr and atomic number 87. It is extremely radioactive.
Down
  1. 1. the chemical element with the symbol K and atomic number 19. It is a silvery white metal that is soft enough to easily cut with a knife.
  2. 3. process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts.
  3. 4. any substance composed of identical molecules consisting of atoms of two or more chemical elements.
  4. 5. the change in position of an object.
  5. 6. a process that leads to the chemical transformation of one set of chemical substances to another.
  6. 7. a salt of carbonic acid, characterized by the presence of the carbonate ion, a polyatomic ion with the formula CO2−3.
  7. 10. an atom or group of atoms that has an electric charge.
  8. 11. the chemical element with the symbol H and atomic number 1. It is the lightest element.
  9. 13. any thermodynamic process with an increase in the enthalpy H of the system. In such a process, a closed system usually absorbs thermal energy from its surroundings, which is heat transfer into the system.
  10. 14. salt.
  11. 19. A chemical that gives off hydrogen ions in water and forms salts by combining with certain metals.