NCERT MCQ Solutions for Class 8 Science Curiosity Chapter 9 The Amazing World of Solutes, Solvents and Solutions

ORS is made by dissolving sugar and salt in water, forming a uniform mixture. All components are evenly distributed, and every sip tastes the same. This kind of mixture as a solution because the solutes are fully dissolved in the solvent.

A solute is the component that gets dissolved. In solid–liquid solutions, such as saltwater, salt is the solute. In liquid–liquid solutions, the substance present in a smaller quantity is called the solute.

The solvent is the component in which the solute dissolves. It is usually present in greater quantity. In most cases like sugar water, water is the solvent. This principle also applies to liquid–liquid and gas mixtures.

When salt dissolves completely in water, the mixture appears uniform. This a solution, where the solute is evenly distributed in the solvent, forming a consistent composition throughout.

When chalk powder is added to water, it does not dissolve. The chalk remains suspended or settles at the bottom. This type of mixture is called non-uniform because the components are not evenly distributed, as explained in the chapter.

Sugar is the substance that dissolves in water to form a uniform solution. Clearly states that in solid–liquid solutions, the solid is called the solute and the liquid is the solvent.

Air is a solution of gases where nitrogen is the most abundant gas. Therefore, nitrogen is the solvent while the other gases like oxygen, argon and carbon dioxide are solutes.

A saturated solution occurs when no more solute can dissolve in the solvent at a given temperature. When undissolved salt settles at the bottom despite stirring.

An unsaturated solution is one that has not reached its maximum solubility. More solute can be added and dissolved. Salt-water experiments to demonstrate this concept clearly.

Solubility is defined in the chapter as the maximum amount of solute that can dissolve in a fixed amount of solvent at a specific temperature. It varies depending on the substance and temperature.

Increasing the temperature of a solvent usually increases the solubility of solids. Warm water allows more sugar or salt to dissolve than cold water. This principle helps in making saturated solutions and is used in many daily-life applications.

Stirring helps distribute the solute particles evenly throughout the solvent. Illustrates that stirring increases contact between solute and solvent, which speeds up the dissolving process. It is one of the key ways to make a solution quickly.

Lemonade is made by dissolving lemon juice, sugar and salt in water. All solutes dissolve in the common solvent (water), forming a uniform solution. 

Water as the universal solvent because it can dissolve a wide variety of substances.
Its molecular properties allow it to interact with many solutes, making it the most commonly used solvent in nature and laboratories.

Adding more sugar increases the concentration of sugar in the solution, making it taste sweeter.
Everyday example to explain how solute concentration affects the properties of a solution like taste.

Sand does not dissolve in water. It settles at the bottom, forming a non-uniform mixture.
Only substances that dissolve and mix uniformly with water form solutions, and sand is not one of them.

Iodine is a solid that dissolves in alcohol, which is a liquid. Such examples to explain that solutions can involve solids dissolving in liquids. The solution formed is uniform and clear, meeting the definition of a solution.

A solute as the substance that dissolves in the solvent and is usually present in a smaller amount. Even in liquid–liquid solutions, the lesser quantity component is termed the solute.

When salt no longer dissolves and settles at the bottom, the solution is saturated. 
Its explains that this occurs when the maximum solubility is reached at a given temperature. Any added salt beyond that remains undissolved.

Dissolving sugar in water does not form a new substance. The sugar retains its properties and can be recovered by evaporation.
This is a physical change, as no new compound is formed during the process.

Chalk does not dissolve in water and remains visible as suspended particles. Its identifies this as a non-uniform mixture, which differs from solutions like saltwater where the solute completely dissolves and cannot be seen.

In soda water, carbon dioxide gas is dissolved in water under pressure. This gas is the solute and water is the solvent. This as an example of a gas–liquid solution.

Sugar dissolves completely in water to form a uniform solution. As a standard example of a solid–liquid solution, where sugar is the solute and water is the solvent.

A clear solution shows that the solute has completely dissolved in the solvent.
No particles are visible in a true solution, which is transparent and consistent throughout.

Whether more solute can be added depends on whether the solution is saturated. If it is not saturated, more solute can dissolve.
Once the saturation point is reached, added solute will remain undissolved.

Stirring distributes solute particles throughout the solvent more effectively. This increases the surface area in contact, allowing faster dissolution. 

When gases like carbon dioxide dissolve in liquids like water, they form uniform solutions.
Soda water is an example given in the chapter. The gas is evenly distributed throughout the liquid when sealed under pressure.

Oil does not dissolve in water. Instead, it floats or forms separate droplets. Oil and water form a non-uniform mixture, not a true solution.

When two liquids dissolve completely in each other, they form a uniform or homogeneous solution. Such solutions where both components are liquids, like vinegar and water.

A true solution must appear clear and have a uniform composition throughout. There should be no visible solute and the entire mixture must look the same, regardless of where it is sampled.