Three substances a, b, and c melt at 00c,500c and -1500c respectively and their boiling points are 1000c , 2000c and 100c. state the physical nature of a, b and c at room temperature

That information is better presented and analyzed in a table.

This table shows you all the information and the answers:

Substance         melting point   boiling point    room temperature    conclusion
                                    °C                  °C                      °C                    (state)

A                                  0                    100                    25                    liquid

B                                  50                  200                    25                    solid
C                               -150                   10                     25                    gas

Explanation:

1) Substance A at 25° is above the melting point and below the boiling point, then it is liquid (just like water)

2) Substance B at 25°C is below the melting point, so it is solid.

3) Substance C at 25°C is above the boiling point, so it is gas.