Chapter 7 Revision Sheet

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Across
  1. 4. dioxide Complete the equation: methane + oxygen —> _____ ______ + water
  2. 5. The shell which can hold up to 18 electrons
  3. 6. An ion with a negative charge
  4. 10. Reactions in which a substance reacts with oxygen and heat is released
  5. 12. A change of state is an example of a _____ change
  6. 13. Chemical reactions that release energy
  7. 14. The substance that reacts with oxygen in a combustion reaction
  8. 15. proportions The law of ... which states that a compound, no matter how it is formed, always contains the same relative amounts of each element.
  9. 16. The new substances that are formed during a chemical reaction
  10. 17. The number that tells you how many molecules are in an equation
  11. 18. of mass The law of … which states that matter can be neither created nor destroyed during a chemical reaction.
  12. 21. reactions What takes place when the bonds between atoms are broken and new bonds are formed, creating a new arrangement of atoms and at least one new substance.
  13. 23. Combustion reactions are examples of ______ reactions
  14. 26. Element represented by the letter K
  15. 27. The ability to do work
Down
  1. 1. Number of electrons the first shell can hold
  2. 2. The number that tells you how many atoms are in a molecule
  3. 3. What Alfred Nobel invented
  4. 4. An ion with a positive charge
  5. 7. Complete the equation: hydrogen + _____ —> water
  6. 8. All chemical equations need to be _______
  7. 9. Chemical reactions that absorb energy from their surroundings
  8. 11. The number that tells you the charge of an ion
  9. 19. The original substances in a chemical reaction
  10. 20. An atom with a different number of protons and neutrons
  11. 22. A charged atom
  12. 24. number The number of protons on an atom. Determines the element
  13. 25. The protons and neutrons in an atom make up the _____