Chapter 7 Revision Sheet

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