Heterogeneous mixtures can often be separated by physical methods.
Explanation
Mixtures are substances composed of two or more forms of matter that are physically combined but not chemically bonded. They are broadly classified into heterogeneous mixtures (non-uniform composition) and homogeneous mixtures (uniform composition). The separation of these mixtures relies on exploiting differences in physical properties such as density, solubility, boiling point, or particle size.
Statement-wise Analysis:
- All mixtures can be separated by simple filtration. is Incorrect: Filtration is a specific physical method used to separate insoluble solids from a liquid. It is effective only for certain heterogeneous mixtures (suspensions) and cannot separate components of homogeneous mixtures (solutions) or liquid-liquid mixtures.
- Heterogeneous mixtures can often be separated by physical methods. is Correct: Heterogeneous mixtures consist of distinct phases with visible boundaries. Because the components remain physically distinct, they can often be separated by simple physical methods such as hand-picking, sieving, filtration, decantation, or magnetic separation.
- Homogeneous mixtures cannot be separated into their constituents. is Incorrect: Homogeneous mixtures (such as salt dissolved in water) can be separated into their constituents. While simple mechanical methods like filtration do not work, other physical methods such as evaporation, distillation, centrifugation, or chromatography are effective.
- Separation of mixtures always requires chemical reactions. is Incorrect: The separation of mixtures is inherently a physical process because the components are not chemically bonded. Chemical reactions are required to decompose compounds into elements, but mixtures are separated using physical techniques without altering the chemical identity of the constituents.
Key Takeaway:
Mixtures are physically combined substances that can be separated using physical methods. Heterogeneous mixtures are often separable by mechanical means (filtration, sieving), whereas homogeneous mixtures typically require methods involving phase changes or density differences (distillation, evaporation).