When you boil water, you aren't changing the elements. You're just making water vapor. However, when you burn paper, it becomes carbon (mostly). So physical changes will not change the substance, only chemical changes will.
O is what should go in the blank. O stands for Oxygen.
The answer is option C.
That is it is a heterogeneous mixture.
Heterogeneous mixture have the following properties:
1. Different components could be observed in the substance.
2. Different samples of the substance appeared to have different proportions of the components.
3.The components could be easily separated using filters and sorting.
The scientist observes at what rate is the concentration increasing or decreasing.
<span>As mentioned, the isomerization of cyclopropane to propylene is a first-order process with a half-life of 19 min at 500°c. A first-order reaction kinetic rates means that the rate is constant throughout the reaction.
Thus, the time it takes for the partial pressure of cyclopropane to decrease from 1 atm to 0.125 atm at 500°c is </span><span>57 minutes.</span>