Classify each of the following as a pure substance or a mixture. If a mixture, indicate whether it is homogeneous or heterogeneous. Drag the appropriate items to their respective bins. baking soda tap water sawdust cola with ice Pure substance Homogeneous mixture Heterogeneous mixture
The Correct Answer and Explanation is:
Classification:
- Baking Soda – Pure substance
Baking soda (sodium bicarbonate, NaHCO₃) is a single chemical compound. It has a consistent composition and properties throughout, so it is classified as a pure substance. - Tap Water – Homogeneous mixture
Tap water is primarily composed of H₂O but contains dissolved minerals, chemicals, and sometimes gases. These components are uniformly distributed, so tap water is considered a homogeneous mixture. Even though it might have trace impurities, they are typically present in such small amounts that they are not visibly distinguishable, maintaining the uniformity of the mixture. - Sawdust – Heterogeneous mixture
Sawdust is a mixture of small wood particles, which can be seen and separated. The components are not uniformly distributed, and you can usually distinguish the different particles, making sawdust a heterogeneous mixture. - Cola with Ice – Heterogeneous mixture
Cola with ice is a heterogeneous mixture because the ice is distinct from the cola. The components (liquid cola and solid ice) can be physically separated, and the ice itself can melt into the liquid, altering the mixture’s composition. Even if the ice melts, the dissolved carbon dioxide from the cola can form bubbles, further contributing to the heterogeneous nature of the system.
Explanation:
- Pure substances consist of a single type of molecule or atom and have uniform properties throughout. Baking soda, being a single chemical compound, meets this criterion.
- Homogeneous mixtures are uniform at the molecular level, meaning the composition is the same throughout the mixture. Tap water, despite containing dissolved substances, remains uniform in appearance and composition, fitting the definition of a homogeneous mixture.
- Heterogeneous mixtures have visibly different components that can be distinguished, even if they’re mixed. Sawdust and cola with ice both have parts that are not uniformly distributed (the wood particles and the ice in the cola, respectively), making them heterogeneous.
