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Q1. A mixture showing Tyndall effect must have
A mixture showing Tyndall effect must have particles of suitable size (1 nm to 100 nm), which is the range for colloidal particles. These particles are large enough to scatter light but small enough to not settle. Very large particles would settle and form a suspension, while very small particles (like in a true solution) would not scatter light at all.
Q2. Tyndall effect can be observed when
The Tyndall effect can be observed when light passes through dusty air. The dust particles scatter the light, making the beam visible. In a vacuum, there are no particles to scatter light. Glass and true solutions do not scatter light either, as their particles are too small or they are transparent with no suspended particles.
Q3. Smoke is an example of
Smoke is an example of an aerosol. An aerosol is a colloidal system where solid particles or liquid droplets are dispersed in a gas. In smoke, solid particles (soot and ash) are dispersed in air (gas). This is why smoke shows the Tyndall effect and is visible in a beam of light.
Q4. Colloids do not settle down when left undisturbed, so they are
Colloids do not settle down when left undisturbed, so they are stable. The particles in a colloid are small enough to remain suspended indefinitely due to Brownian motion. This stability is a key characteristic of colloidal solutions, distinguishing them from suspensions where particles settle.
Q5. A suspension is a
A suspension is a heterogeneous mixture because its composition is not uniform throughout. The suspended particles can be seen and settle on standing, making different parts of the mixture have different properties. The components remain physically distinct.
Q6. Evaporation separates
Evaporation separates a volatile solvent from a non-volatile solute. When a solution is heated, the solvent (which has a lower boiling point) evaporates, leaving behind the solute. This method is commonly used to separate salt from saltwater. The solvent is volatile (evaporates easily), while the solute is non-volatile (does not evaporate).
Q7. A colloidal solution is actually a
A colloidal solution is actually a heterogeneous mixture. Although it appears uniform to the naked eye, it is not a true solution. The particles are large enough to scatter light and are not completely dissolved. Under a microscope, the two phases (dispersed phase and dispersion medium) can be distinguished.
Q8. Filtration fails for very small solid particles because
Filtration fails for very small solid particles because they pass through the pores of the filter paper. Filter paper can only trap particles larger than its pore size. Very small particles (like those in colloids or solutions) go through with the liquid, so filtration cannot separate them.
Q9. Coloured gemstone is an example of
A coloured gemstone is an example of a solid sol. In a solid sol, the dispersed phase is a solid and the dispersion medium is also a solid. For example, ruby is a solid sol where tiny particles of chromium oxide are dispersed in a solid aluminium oxide (corundum) matrix, giving it its red colour.
Q10. Tyndall effect is seen in a room due to scattering by
The Tyndall effect is seen in a room due to scattering by dust and smoke particles. When sunlight enters a room, the dust and smoke particles present in the air scatter the light, making the beam visible. Oxygen, carbon dioxide, and water vapour molecules are too small to scatter light.
Q11. Such very small particles are separated by
Very small particles that cannot be separated by filtration are separated by centrifugation. Centrifugation uses the principle of centrifugal force—when a mixture is spun rapidly, the heavier particles move to the bottom, and the lighter particles stay at the top. This method is used to separate colloids and fine suspensions.
Q12. Colloids are common in
Colloids are common in everyday life. Many substances we encounter daily are colloidal in nature. Examples include milk, butter, fog, smoke, ink, jelly, and even blood. Colloids are not limited to laboratories or chemical plants—they are part of our daily environment.
Q13. Fog is an example of
Fog is an example of an aerosol. In fog, tiny water droplets (liquid) are dispersed in air (gas). This makes it a liquid-in-gas colloid. The Tyndall effect is often seen in fog when light from car headlights is scattered by the water droplets.
Q14. Milk varieties differ mainly in the amount of
Milk varieties differ mainly in the amount of fat they contain. For example, whole milk has about 3-4% fat, toned milk has about 3% fat, and skimmed milk has less than 0.5% fat. The fat content determines the richness, taste, and nutritional value of milk.
Q15. The component that evaporates during evaporation is
The component that evaporates during evaporation is the solvent. When a solution is heated, the solvent (being volatile) turns into vapour and escapes into the air, leaving behind the non-volatile solute as a residue. For example, when saltwater is heated, water (solvent) evaporates, leaving salt (solute) behind.
Q16. Mist contains tiny droplets of
Mist contains tiny droplets of water. Mist is formed when water vapour condenses into small water droplets suspended in air. It is a type of aerosol (liquid-in-gas colloid). Mist is similar to fog but is usually less dense and forms in the morning or near water bodies.
Q17. The two main components of a colloid are
The two main components of a colloid are the dispersed phase and the dispersion medium. The dispersed phase is the substance that is distributed as particles, and the dispersion medium is the substance in which the particles are dispersed. This terminology is specific to colloids and distinguishes them from true solutions (solute and solvent).
Q18. Most natural substances are
Most natural substances are not chemically pure. They are mixtures of various components. For example, milk contains water, fat, protein, and minerals. Air is a mixture of gases. Soil contains minerals, organic matter, and water. Even natural water contains dissolved minerals and gases.
Q19. Milk is an example of a
Milk is an example of a colloid (specifically an emulsion). It contains fat globules (dispersed phase) dispersed in water (dispersion medium). The fat globules are intermediate in size, making milk a colloidal system. This is why milk appears opaque and shows the Tyndall effect.
Q20. Colloidal particles cannot be seen by naked eyes because
Colloidal particles cannot be seen by the naked eye because they are very small in size (1 nm to 100 nm). They are larger than molecules but smaller than particles in a suspension. While they are too small to be seen individually, they can scatter light (Tyndall effect) and can be observed collectively.
Q21. The Tyndall effect is named after the
The Tyndall effect is named after the scientist John Tyndall, who discovered and studied this phenomenon. He observed that light is scattered by particles in colloidal solutions and suspensions. The scattering of light by particles is now known as the Tyndall effect in his honour.
Q22. Ink is a mixture of
Ink is a mixture of dye (or pigment) and water (or sometimes alcohol). Ink is a colloidal solution where the dye particles are dispersed in the liquid medium. Different types of ink may have different compositions, but the basic mixture is dye dissolved or dispersed in a liquid.
Q23. Colloidal mixtures are best described as
Colloidal mixtures are best described as apparently homogeneous but actually heterogeneous. To the naked eye, they appear uniform (homogeneous), but under a microscope or when light is passed through them, they show two distinct phases. The dispersed particles are not completely dissolved, making them heterogeneous at the particle level.
Q24. A colloidal mixture appears homogeneous because
A colloidal mixture appears homogeneous because its particles are very small (1 nm to 100 nm). These particles are too small to be seen individually, so the mixture looks uniform to the naked eye. However, they are large enough to scatter light and show the Tyndall effect, revealing their heterogeneous nature.
Q25. Suspension differs from colloid because suspension particles
Suspension differs from colloid because suspension particles settle down when left undisturbed. In a suspension, the particles are larger than 100 nm and are heavy enough to be pulled down by gravity. Colloidal particles (1-100 nm) are small enough to remain suspended indefinitely due to Brownian motion.
Q26. Centrifugation works on the principle that
Centrifugation works on the principle that denser particles move to the bottom when a mixture is spun rapidly. The centrifugal force pushes heavier particles outward and downward, while lighter particles remain near the top. This is used to separate components based on their density, such as cream from milk or sediment from a suspension.
Q27. Dispersion medium refers to
Dispersion medium refers to the medium in which particles are suspended in a colloid. It is the continuous phase that surrounds the dispersed particles. For example, in milk, water is the dispersion medium, and fat globules are the dispersed phase. The dispersion medium can be a solid, liquid, or gas.
Q28. Colloidal particles are
Colloidal particles are uniformly spread throughout the dispersion medium. They do not settle on standing, and they are not dissolved completely. They remain distributed evenly, giving the colloid its apparent homogeneous appearance. This uniform distribution is maintained by Brownian motion.
Q29. A true solution does not show Tyndall effect because
A true solution does not show the Tyndall effect because its particles are too small (less than 1 nm). These particles are at the molecular or ionic level and do not interfere with the path of light. Light passes through a true solution without being scattered, so no visible beam is seen.
Q30. Scattering of light by colloidal particles is called
The scattering of light by colloidal particles is called the Tyndall effect. When a beam of light passes through a colloid, the particles scatter the light, making the beam visible. This is different from reflection (bouncing off a surface), refraction (bending of light), and dispersion (splitting of light into colours).
Q31. Ink is separated by the method of
Ink can be separated by distillation. In this process, the liquid component (solvent) is heated and evaporated, and then condensed back into liquid. This separates the solvent from the dye or pigment particles. Filtration cannot separate ink because the particles are too small to be trapped by filter paper.
Q32. The dispersed phase in fog consists of
The dispersed phase in fog consists of water droplets. Fog is a colloidal system where tiny water droplets (liquid) are dispersed in air (gas). These water droplets are small enough to remain suspended but large enough to scatter light, which is why fog appears white and reduces visibility.
Q33. Milk of magnesia is an example of
Milk of magnesia is an example of a sol. A sol is a colloidal system where a solid is dispersed in a liquid. In milk of magnesia, solid magnesium hydroxide particles are dispersed in water. This is why it appears as a milky white liquid. It is a suspension-like colloid that remains stable for some time.
Q34. Sunlight passing through a dense forest shows Tyndall effect due to
Sunlight passing through a dense forest shows the Tyndall effect due to the mist droplets present in the air. The tiny water droplets in the mist scatter the light, creating visible beams of sunlight (often called “god rays”). Leaves and tree trunks do not cause the scattering of light in the air.
Q35. Colloidal particles can be separated by
Colloidal particles can be separated by centrifugation. Since the particles are too small to be filtered, high-speed spinning is used to force the particles to settle at the bottom. This is an effective method for separating colloids. Filtration, crystallisation, and evaporation are not suitable for separating colloids.
Q36. Handpicking, sieving and filtration are
Handpicking, sieving, and filtration are physical methods of separation. They do not involve any chemical reactions or changes in the chemical composition of the substances. These methods rely on physical properties like size, shape, or state of matter to separate mixtures.
Q37. Milk is classified as
Milk is classified as an emulsion. An emulsion is a colloidal system where both the dispersed phase and the dispersion medium are liquids. In milk, fat globules (liquid) are dispersed in water (liquid). Emulsions are common in food products and are stabilized by emulsifying agents like proteins in milk.
Q38. Colloids cannot be separated by
Colloids cannot be separated by filtration because the particles are too small to be trapped by filter paper. They pass through the pores along with the liquid. Handpicking is not suitable due to the small particle size, and sedimentation is not effective because colloidal particles do not settle. Centrifugation, however, can separate colloids.
Q39. Separation of mixtures helps to
Separation of mixtures helps to study individual components. By separating a mixture, we can analyse the properties, composition, and behaviour of each component. This is essential in chemistry, industry, and everyday life for obtaining pure substances and understanding their characteristics.
Q40. Cream is separated from milk by
Cream is separated from milk by centrifugation. Milk is spun rapidly in a centrifuge, causing the lighter fat particles (cream) to move to the top and the heavier skimmed milk to settle at the bottom. This process is used in the dairy industry to produce cream and skimmed milk.
Q41. Colloids are classified based on
Colloids are classified based on the state of the dispersed phase and the dispersion medium. Depending on whether the dispersed phase and medium are solids, liquids, or gases, colloids are classified into different types such as sols, gels, emulsions, aerosols, and foams. This classification helps in understanding their properties and applications.
Q42. In centrifugation, lighter particles
In centrifugation, lighter particles stay at the top while heavier particles move to the bottom. The centrifugal force pushes the denser particles outward and downward, leaving the lighter particles near the centre or top. This is how centrifugation separates components based on their density.
Q43. Jelly is an example of
Jelly is an example of a gel. A gel is a colloidal system where a liquid is dispersed in a solid (or semi-solid) medium. Jelly has a solid-like structure but contains liquid trapped within it. Other examples of gels include curd, cheese, and certain cosmetics.
Q44. Colloidal particles scatter light due to
Colloidal particles scatter light due to their suitable particle size (1 nm to 100 nm). This size is large enough to interact with and scatter light waves but small enough to remain suspended. The scattering of light by these particles is what causes the Tyndall effect.
Q45. Which does NOT show Tyndall effect?
Copper sulphate solution does NOT show the Tyndall effect because it is a true solution. The copper sulphate particles are too small (less than 1 nm) to scatter light. Fog, smoke, and milk are all colloids that show the Tyndall effect because they contain particles large enough to scatter light.
Q46. The dispersing medium in fog is
The dispersing medium in fog is gas (air). In fog, tiny water droplets (liquid) are dispersed in air (gas). Since air is the medium in which the droplets are suspended, it is the dispersing medium. Fog is a liquid-in-gas colloid (aerosol).
Q47. Dispersed phase refers to
The dispersed phase refers to the solute-like particles in a colloid. These are the particles that are distributed throughout the dispersion medium. They are analogous to the solute in a solution, but they are not completely dissolved—they remain as distinct particles. In fog, the water droplets are the dispersed phase.
Q48. The mixture obtained by group D is called a
Based on typical class experiments, group D obtained a true solution. When substances like salt or sugar are dissolved in water, they form a clear solution where the particles are completely dissolved and cannot be seen. The mixture is homogeneous and stable.
Q49. Heterogeneous mixtures can be separated by
Heterogeneous mixtures can be separated by simple physical methods such as handpicking, sieving, filtration, sedimentation, and centrifugation. These methods rely on differences in physical properties like size, density, or state of matter. No chemical reactions are needed.
Q50. Shaving cream is an example of
Shaving cream is an example of a foam. A foam is a colloidal system where a gas is dispersed in a liquid or solid medium. In shaving cream, air bubbles (gas) are trapped in a liquid (or semi-solid) medium. This gives it a light, fluffy texture. Other examples include froth, beaten egg whites, and foam rubber.