Consider the following statements about mixture: 1. A substance can be separated into other kinds of matter by any physical process. 2. Dissolved sodium chloride can be separated from water by the physical process of evaporation. Which of these statements given above is/are correct?
2 only
Analyzing Statements on Mixture Separation by Physical Processes
Let's carefully examine each statement provided about mixtures and their separation methods using physical processes.
Statement 1: A substance can be separated into other kinds of matter by any physical process.
To understand this statement, we need to clarify the term "substance". In chemistry, a substance refers to either an element or a compound. Elements are the simplest forms of matter and cannot be broken down into simpler substances by chemical or physical means. Compounds are formed from elements chemically combined in a fixed ratio. Compounds can only be broken down into their constituent elements by chemical processes, not physical ones.
Mixtures, on the other hand, are composed of two or more substances that are not chemically combined. The components of a mixture retain their individual properties and can often be separated by physical processes.
The statement claims "A substance" (implying an element or compound) can be separated into "other kinds of matter" by "any" physical process. This is incorrect because:
- Elements cannot be separated into other kinds of matter.
- Compounds require chemical processes (like electrolysis or chemical reactions) to be broken down into elements, not physical processes.
- While mixtures (which are not substances in the chemical sense) can be separated by physical processes, the statement specifically says "A substance". Also, not *any* physical process will work for a given mixture; the appropriate physical process depends on the properties of the components.
Therefore, Statement 1 is incorrect.
Statement 2: Dissolved sodium chloride can be separated from water by the physical process of evaporation.
Sodium chloride (common salt) dissolved in water forms a solution, which is a type of mixture. Sodium chloride is the solute (the substance that dissolves), and water is the solvent (the substance that does the dissolving). In this solution, the sodium chloride and water are physically mixed, not chemically combined.
Evaporation is a physical process where a liquid turns into a gas. When a sodium chloride solution is heated or left exposed to air, the water molecules gain energy and escape as water vapor. The solid sodium chloride, which has a much higher boiling point, is left behind as a residue.
This method is commonly used to obtain salt from saltwater. Since evaporation is a physical process and it successfully separates the dissolved sodium chloride from the water in the mixture, Statement 2 is correct.
Conclusion on the Statements
- Statement 1 is incorrect because substances (elements and compounds) cannot be separated into other kinds of matter by physical processes in general; elements cannot be separated, and compounds need chemical processes.
- Statement 2 is correct because evaporation is a physical process that effectively separates a dissolved solid (sodium chloride) from a liquid (water) in a solution (a type of mixture).
Based on this analysis, only Statement 2 is correct.
The final answer is option 2 because only Statement 2 is correct.
| Feature | Substance (Element or Compound) | Mixture (like Saltwater) |
|---|---|---|
| Composition | Fixed composition | Variable composition |
| Separation into components | Elements: Cannot be separated Compounds: By chemical processes only |
By physical processes |
| Properties | Specific, fixed properties | Properties of components retained |
Revision Table: Key Concepts
| Term | Definition | Separation Method (Examples) |
|---|---|---|
| Element | Pure substance made of only one type of atom. Cannot be broken down further. | N/A (cannot be separated) |
| Compound | Pure substance made of two or more elements chemically combined. | Chemical processes (e.g., electrolysis) |
| Mixture | Two or more substances physically mixed. | Physical processes (e.g., filtration, evaporation, distillation, decantation, magnetism) |
| Physical Process | Process that changes the form or appearance of a substance but not its chemical composition. Used to separate mixtures. | Evaporation, Filtration, Distillation |
| Chemical Process | Process that involves a chemical reaction, changing the chemical composition of a substance. Used to break down compounds. | Electrolysis, Decomposition Reaction |
Additional Information on Separation Techniques
Understanding different separation techniques is crucial when studying mixtures. Physical separation methods exploit the differences in physical properties of the components of a mixture.
Examples of common physical separation techniques include:
- Evaporation: Used to separate a soluble solid from a liquid. The liquid is vaporized, leaving the solid behind. (As seen with salt and water)
- Filtration: Used to separate an insoluble solid from a liquid using a filter paper. The liquid passes through, while the solid is retained.
- Decantation: Used to separate a liquid from a solid that has settled at the bottom, or to separate two immiscible liquids by carefully pouring off the top layer.
- Distillation: Used to separate liquids with different boiling points or to separate a liquid from a dissolved solid by boiling and then condensing the vapor.
- Magnetism: Used to separate magnetic substances from non-magnetic substances.
- Chromatography: Used to separate components of a mixture based on their differential partitioning between a stationary phase and a mobile phase.
These physical methods are effective for separating the components of mixtures because the substances in a mixture are not chemically bonded and retain their individual physical properties. Substances (elements and compounds) themselves require chemical methods (for compounds) or cannot be separated further (elements).
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