Which of the following can best be described as en element or compound that cannot be physically separated?

Use the drop-down menus to match each part of the scenario to the correct scientific practice. akira records the speed of a reaction without a catalyst and then with a catalyst. akira creates a reaction without a catalyst and repeats the reaction with a catalyst. akira turns in a written lab report to his science teacher. akira wonders, "will adding a catalyst speed up this chemical reaction? " akira writes in his notes that adding a catalyst sped up the chemical reaction because the catalyst lowers the activation energy needed to get the reaction started.