Asap! an unknown substance is heated from 10 °c to 25 °c. the table below shows the state of the substance at different temperatures.

time (minutes) temperature (degrees celsius) state of matter
0 10 liquid
2 15 liquid
4 20
6 20
8 20
10 23 gas
12 25 gas

which statement is correct about the unknown substance?
its boiling point is 20 °c.
its boiling point is 15 °c.
the substance sublimes at 15 °c.
the substance exists as a solid at 20 °c.

Answer is A) It's boiling point is 20 degree C.

Explanation: Boiling point is the temperature at which a liquid starts boiling and converting into gas.

Looking at the given data, The substance is a liquid at 0 degree C and after heating for 2 minutes its still liquid, On further heating for next 6 minutes(total 8 minutes from starting) the temperature remains constant that indicates a phase change. Since, the substance was initially a liquid, so at 20 degree C the boiling starts and it turns into a gas.

Further heating increases the temperature but the phase does not change and hence its a gas beyond 20 degree C like at 23 degree C and 25 degree C.

So, the right answer is A) It's boiling point is 20 degree C.

the density of gold = 19.3 g/cm3

the relation between density and mass and volume is

density = mass / volume

given :

mass of gold = 13 g

density = 13g / volume = 19.3

volume = 13 /19.3 = 0.67 cm^3

thus volume of gold nugget = 0.67 cm^3