You are asked to determine the identity of an unknown liquid and can measure only one physical property. you see the liquid and record that's liquid turn into vapor at 100 degrees celsius. this demonstrates which physical property

The physical property you measured is the boiling point of the liquid.

Therfore, if the liquid has a boiling point of 100°C, it turns from liquid state to vapor when you heat it up to 100°C.

To conclude, The liquid should be pure water. Because only pure water has a boiling point of 100°C, using this physical property, we can test whatever liquid ans see if it's pure water or not, this test is called the boiling point test.

Ithink 2 is the correct

Neither model is able to show the reactivity of potassium.