Which observations is the best evidence that unknown liquid X is a composed of only pure substance

A substance that is composed only of atoms having the same atomic number is ...  36 grams of an unknown liquid at its boiling point,.

hi,

the answer is d, it has indefinite shape but definite volume.

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answer: the rate of diffusion increases with increase in temperature.

increase in temperature, increases the molecular/particles speed (kinetic energy. diffusion means movement of particles through the material.

generally, the heavier the particle the more it interacts with the environment and more the temperature matters. so higher temperature results in higher diffusion.