Iodine crystals sublime. Describe what sublimation means. Is sublimation a physical or chemical change? 7. Explain how it is possible to have a heterogeneous mixture and still have only one pure substance present. Give an example. 8. Explain how it is possible to have a homogeneous mixture of two different compounds. Give an example.
The Correct Answer and Explanation is:
Sublimation:
Sublimation is the process by which a substance changes directly from a solid to a gas, skipping the liquid phase entirely. It occurs when the molecules in a solid gain enough energy to overcome the forces that hold them together, transitioning into the gas phase. A common example is iodine crystals, which directly sublimate into iodine gas when heated. In this case, the solid iodine turns into a violet vapor. Sublimation is a physical change because the chemical composition of the substance does not change; iodine remains iodine whether it’s in its solid or gaseous form.
Heterogeneous Mixture and Pure Substance:
A heterogeneous mixture contains more than one phase or component that can be visually distinguished. However, it is possible for a heterogeneous mixture to contain only one pure substance if the components are not chemically combined but are merely physically mixed. For example, a mixture of sand and iron filings may look heterogeneous, but each component is still a pure substance (sand is SiO2, and iron is Fe). In this case, the components can be separated without altering their chemical structures.
Homogeneous Mixture of Two Different Compounds:
A homogeneous mixture of two different compounds refers to a mixture where the components are uniformly distributed at a molecular or ionic level. An example would be a solution of salt (NaCl) dissolved in water. Here, water (H2O) and salt (NaCl) are chemically distinct compounds, but they form a single, uniform mixture. The salt dissolves into its constituent ions (Na+ and Cl-) and is distributed evenly throughout the water, making the mixture appear uniform even though two different compounds are present.
