Q1.
According to science, how would you classify milk, packed fruit juice, baking soda, sugar, and soil — as mixtures or pure substances?
Answer
Only baking soda and sugar are pure substances. The other three are mixtures, however "pure" the label on the pack may claim to be.
| Substance | Classification | Reason |
|---|---|---|
| Milk | Mixture | Water, fat, proteins, sugar and minerals together; the fat can be separated as cream, which is a physical process |
| Packed fruit juice | Mixture | Water, fruit pulp, sugar, acids and often added colour and preservative |
| Baking soda | Pure substance (a compound) | Made of only one kind of particle; no physical process can split it into other kinds of matter |
| Sugar | Pure substance (a compound) | Only one kind of particle; on heating it breaks into carbon and water, but that is a chemical change, not a physical one |
| Soil | Mixture | Sand, clay, humus, water, air and minerals — you can see the different bits |
Why it happens: The everyday word "pure" means unadulterated — nothing cheap or harmful added. Science asks a stricter question: does the substance consist of only one type of particle? Milk with nothing added to it is still unadulterated milk, but it is scientifically impure, because it is made of more than one substance.