Answer:
5.1 Crystal structure and habit.
5.2 Hardness.
5.3 Lustre and diaphaneity.
5.4 Colour and streak.
5.5 Cleavage, parting, fracture, and tenacity.
5.6 Specific gravity.
5.7 Other properties.
The density of an object determines whether it will float or sink in another substance. An object will float if it is less dense than the liquid it is placed in. An object will sink if it is more dense than the liquid it is placed in.
Beryllium fluoride I believe is the correct answer
The reduction reaction is the gain of electrons while oxidation reaction is the loss of electrons. For potassium ion(K+), the reaction should be K+ + e- ==> K. So the answer is (1).