day and night is the main way you can tell as well as the stars moving across the sky, and we can tell it rotates by looking at the sky and seeing the sun move across the sky during the day.
Some physical properties change, but the substance keeps its identity.
When dealing with these kind of questions, understand that the keyword here is physical change. Thus, all options that says no physical properties change are WRONG. So this leaves us with only 2 answers left. However, this is a physical change, no chemical change. Thus, the substance will keep its identity and not change.
The number of transferred electrons to form the ionic bond in one formula unit of each compound is as below
NaCl = 1 electron
CaS = 2 electrons
BaO= 2 electrons
KBr=1 electrons
LIF = 1 electron
explanation
ionic bond is formed between a metal and a nonmetal . This bond is formed when electron are transferred between cation and anion. To know how many electrons transferred you look the oxidation state of the metal.
for example
in NaCl only one electrons is transferred since Na is in oxidation state of +1. Na donate the one electron to Cl to form an ionic bond. Ba is in oxidation state of 2+ and hence it donate the two electrons to O to form ionic bond.
