Complete the crossword, then click on "Check" to check your answer. If you are stuck, you can click on "Hint" to get a free letter. Click on a number in the grid to see the clue or clues for that number.

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 Check 

Across: 1. The many unusual properties of ___ are mainly due to hydrogen bonding. 3. A substance's molar heat of vaporisation is measured at its ___ point. 6. The ionic radius of a negative ion is ___ than the atomic radius of its parent atom. 9. Heats of combustion are determined on substances in their ___ states. 12. A substance's molar heat of fusion is measured at its ___ point. 14. First ionisation energies ___ going down a group (eg He to Kr). 15. The ionic radius of a positive ion is ___ than the atomic radius of its parent atom. 16. Heat measures the ___ of the kinetic energies of all the particles in a sample. 17. ___ bonding occurs when H is bonded to N, O or F. 19. Their more awkward ___ keeps molecules of cis isomers further apart than their trans equivalents. 20. Molecular substances have relatively low melting points because __ __ __ forces are weak. 22. The general trend is for first ionisation energies to ___ going across a period (from Na to Ar). 24. Bond energies and ionisation energies are always measured on substances in the ___ state. 25. Atomic radii increase going ___ a group of the periodic table. 26. Straight-chain alkanes have ___ boiling points than their branched-chain isomers. 27. When substances change phase (state) the ___ energy of the particles is changing. 28. Bond breaking is an ___ process.

Down: 2. Electronegativities increase going ___ the periodic table. 4. Van der Waals' forces between ___ molecules are also known as dispersion forces or London forces. 5. Enthalpies of combustion are always ___ (positive or negative?). 6. ∆vapH indicates the strength of the forces holding the particles together in the ___ state. 7. The zig-zag shape of the graph showing first ionisation energies against atomic number reveals evidence of the electron ___ within each energy level. 8. Bond making is an ___ process. 10. Tables of bond energies show the ___ energy from bonds in many compounds. 11. The second ionisation energy of an element is always ___ than the first. 13. Non-metal atoms have ___ electronegativities. 18. Enthalpies of combustion relate to the complete combustion of ___ of the substance. 19. ∆fusH indicates the strength of the forces holding the particles together in the ___ state. 21. At 0 kelvin particles have no ___ energy. 23. Bond energies relate to the breaking of a bond to form separate ___.