Final answer:
To determine if substances are the same or different, first establish if it's chemically pure, distinguishing between an element and a compound. Then determine if it's a mixture; heterogeneous mixtures have visibly different constituents, while homogeneous mixtures look uniform. Lastly, use melting/boiling points and chromatography to test for purity.
Step-by-step explanation:
To determine whether substances are different or the same, you should first decide if a substance is chemically pure. Chemically pure substances include elements and compounds. If you can separate a substance into elements, it is a compound. Otherwise, you may be dealing with an element.
Next, assess if the substance is a mixture. A mixture exists in either a heterogeneous or homogeneous form. In a heterogeneous mixture, you can distinguish different components by sight, such as salt and pepper. However, in a homogeneous mixture, such as salt dissolved in water, the composition appears uniform throughout.
To test for purity, melting and boiling points can be useful. Pure substances have sharp melting and boiling points, while mixtures have a range. Chromatography is another method for separating substances into their components, revealing the purity of the substance in question.