The two properties which are used to define matter are that it has mass
and it takes up space. The other properties do not necessarily apply to
each matter. Such some matter can be a conductor of heat (such as metal)
and some not (such as non metals). Likewise, some matter can be buoyant
and float on liquid of density more than it but others would not on the
liquids of density less than it. In-fact not all the matters are
conductors of energy (such as heat, sound, electricity) or at-least a
very poor conductor of energy and tend to find application as
insulating agents (non conductors). So the only thing which is
necessarily true is that the matter would definitely have mass in even
their minutest form as atom and would take up some space.
Answer: 0.0624 atm
Explanation:-
According to the ideal gas equation:

P = Pressure of the gas = ?
V= Volume of the gas = 45.0 L
T= Temperature of the gas = -10.0°C = 263 K 
R= Gas constant = 0.0821 atmL/K mol
n= moles of gas
Moles of gas=

The pressure of sulfur hexafluoride gas in the reaction vessel after the reaction is 0.0624 atm
The answer to this item depends entirely to the chemical reaction. If the compound, NH4Cl, is in the left hand side of the reaction, when it is added, the reaction will shift to the left. In the same manner, when the compound is in the right-hand side of the reaction, the reaction will shift to the right.
This happens because initially the reaction is in equilibrium and adding another compound to it will most likely lead to the shifting of the reaction.