1. What is a pure substance?

A pure substance is a form of matter that has a constant composition and contains only one type of particle.

2. Define mixture and give examples.

A mixture is a combination of two or more substances where no chemical reaction occurs. Examples include air, seawater, and soil.

3. What is a solution and how is it different from other mixtures?

A solution is a homogeneous mixture where one substance is dissolved in another. Unlike other mixtures, solutions do not scatter light and cannot be separated by filtration.

4. Give examples of colloids and suspensions.

Colloids include milk and fog, while suspensions include mud and sand in water, which can be separated over time.

5. What are techniques for separating mixtures?

Techniques for separating mixtures include filtration, evaporation, distillation, and chromatography.

6. Explain physical and chemical changes with examples.

Physical changes affect form but not composition (e.g., melting ice), while chemical changes result in new substances (e.g., burning wood).

7. What is the significance of understanding pure substances vs. mixtures?

Understanding the difference helps in areas like chemistry, medicine, and food science, influencing how substances are handled and utilized.

8. What is evaporation, and how can it be utilized?

Evaporation is the process where liquid turns into vapor. It can be utilized in separation processes, like obtaining salt from seawater.

9. How can mixtures be classified?

Mixtures can be classified as homogeneous or heterogeneous based on their composition and appearance.

10. Describe the importance of sieving in separation of mixtures.

Sieving is important for separating particles based on size, widely used in baking and construction industries.

1. A ______ is a homogeneous mixture of two or more substances.

Answer: solution

2. The method of separating solids from liquids using a filter is called ______.

Answer: filtration

3. A ______ mixture has a uniform composition throughout.

Answer: homogeneous

4. In a ______, the particles do not settle down over time.

Answer: colloid

5. The ______ change involves a change in the composition of a substance.

Answer: chemical

6. Common kitchen salt is a ______ substance.

Answer: pure

7. ______ is the separation technique used for obtaining pure water from seawater.

Answer: distillation

8. A mixture of iron filings and sulfur can be separated through a ______ process.

Answer: magnetism

9. The process of ______ involves changes in the state of matter without changing the chemical composition.

Answer: physical change

10. Solutions can be separated by ______, which involves changing the phase of one component.

Answer: evaporation

1. Which of the following is a pure substance?

a) Milk

b) Air

c) Gold

d) Soil

Answer: c) Gold

2. What method is used to separate a mixture of sand and salt?

a) Filtration

b) Decantation

c) Distillation

d) Evaporation

Answer: d) Evaporation

3. Which of the following is not a physical change?

a) Melting of ice

b) Dissolving sugar in water

c) Burning of wood

d) Shredding paper

Answer: c) Burning of wood

4. Which type of mixture cannot be separated by filtration?

a) Suspension

b) Colloid

c) Solution

d) All of the above

Answer: c) Solution

5. What technique would you use to separate colored pigments in a mixture?

a) Filtration

b) Distillation

c) Chromatography

d) Evaporation

Answer: c) Chromatography

6. Which of the following mixtures is homogenous?

a) Oil and water

b) Sand in water

c) Saltwater

d) Soil

Answer: c) Saltwater

7. What is the main characteristic of a heterogeneous mixture?

a) It has uniform composition.

b) Its properties vary in different parts.

c) It cannot be separated.

d) It is always in a liquid state.

Answer: b) Its properties vary in different parts.

8. Which of these methods can be used to separate a mixture of salt and sand?

a) Filtration

b) Magnetic separation

c) Evaporation

d) Both a and c

Answer: d) Both a and c

9. The term ‘solvent’ refers to:

a) The substance that gets dissolved.

b) The substance that dissolves another substance.

c) Both solvent and solute.

d) None of the above.

Answer: b) The substance that dissolves another substance.

10. Which separation technique could be used to obtain pure alcohol from a mixture?

a) Filtration

b) Distillation

c) Chromatography

d) Evaporation

Answer: b) Distillation

1. Differentiate between homogeneous and heterogeneous mixtures with examples.

Answer: Homogeneous mixtures have uniform composition throughout (e.g., sugar solution), while heterogeneous mixtures have non-uniform composition (e.g., oil and water mixture).

2. Describe the process of filtration and its applications.

Answer: Filtration is used to separate solids from liquids using a filter paper. It is commonly used in laboratories and in the food industry for clarification processes.

3. Explain the importance of chromatography in separating substances.

Answer: Chromatography is important for separating and analyzing components in a mixture, such as pigments in ink, and is widely used in chemistry and forensic analysis.

4. Discuss the applications of distillation in the purification of liquids.

Answer: Distillation is used in the production of spirits, purification of seawater into fresh water, and refining petroleum. It separates components based on their boiling points.

5. Compare and contrast physical and chemical changes with examples.

Answer: Physical changes affect the state or appearance without altering composition, e.g., melting ice. Chemical changes result in new substances, e.g., rusting of iron.

6. Elaborate on the various methods of purifying water.

Answer: Methods include filtration, distillation, chlorination, and reverse osmosis, each addressing specific contaminants to ensure safe drinking water.

7. Discuss how the properties of mixtures affect their separation techniques.

Answer: The physical properties such as size, density, and solubility influence the choice of separation techniques—larger particles might be removed using filtration while soluble substances might require distillation.

8. Explain the concept of a saturated solution.

Answer: A saturated solution is one in which no more solute can be dissolved at a given temperature, resulting in equilibrium between dissolved and undissolved solute.

9. How does temperature affect the solubility of solids in liquids?

Answer: Generally, an increase in temperature increases the solubility of most solids in liquids, allowing more solute to dissolve.

10. What are the factors that influence the rate of dissolution?

Answer: Factors include temperature, stirring, particle size of the solute, and nature of the solute and solvent.