Answer: Option (b) is the correct answer.
Explanation:
It is known that metals are the species which readily lose an electron and tend to attain a positive charge.
For example, atomic number of sodium is 11 and its is an alkali metal. It electronic distribution is 2, 8, 1.
And, in order to attain stability it readily loses an electron and thus it become 
ion.
Also, it is known that species which tend to transfer or donate their valence electrons to other atoms tend to form ionic bond and the compound formed is known as ionic compound.
Therefore, we can conclude that the statement metal atoms held together by ionic bonds best describes a metal solid.
Answer:
Amount of gas
Explanation:
The combined gas law has to do with pressure, volume, and temperature. All of them can be a variable that you have to solve for. However, amount of gas is not a variable you can solve for, which means it must remain constant.
Answer:
The warmer, lighter air rises, bringing cooler, heavier air to low altitudes.
Air at higher altitudes doesn't have as much air weighing down on it from above.
Explanation:
In short - air pressure is the result of the cumulative force that air molecules act on objects below them due to Earth's gravity. The higher the altitude, the less air molecules there are to act a force below them, and therefore, there's less air pressure at higher altitudes.
A hypothesis is given to explain a phenomena which has not been
explained till then.
it can be supported by an experiment if that experiment gets the other
results regarding that particular phenomena in agreement with that being
predicted by the hypothesis
Answer: d) -705.55 kJ
Explanation:
Heat of reaction is the change of enthalpy during a chemical reaction with all substances in their standard states.
Reversing the reaction, changes the sign of 
On multiplying the reaction by 
, enthalpy gets half:
Thus the enthalpy change for the given reaction is -705.55kJ
