Final answer:
A compound has a definite composition and distinct properties and cannot be physically separated into its elements, distinguishing it from a mixture which can be separated and whose components retain their own properties.
Step-by-step explanation:
A compound differs from a mixture in that a compound has a definite and uniform composition throughout and cannot be separated into its individual elements through physical means. For example, sodium chloride (table salt) is a compound formed from the elements sodium and chlorine that cannot be broken down by filtering or distillation. On the other hand, mixtures, such as salt mixed with pepper, can be separated into their pure substances, because no chemical bonding occurs between the components of a mixture. Mixtures can be either homogeneous, with a uniform composition throughout, or heterogeneous, where the composition varies.
Compounds have unique chemical and physical properties differing from the elements they are composed of. While many compounds decompose into their elements upon heating, such as sugar into carbon and water, this is not a defining characteristic for all compounds; for instance, water cannot be decomposed into hydrogen and oxygen by heat alone but requires electrolysis.