Notes

ure! Here's a question paper set on the topic "Matter in Our Surroundings" in chemistry. It includes multiple-choice questions (MCQs), fill in the blanks, short questions, and long questions, along with their respective answers.

Question Paper: Matter in Our Surroundings

Section A: Multiple Choice Questions (MCQs)
Instructions: Choose the most appropriate answer from the options given and write the corresponding letter in the space provided.

Which of the following is an example of a physical change?
(a) Rusting of iron
(b) Burning of wood
(c) Melting of ice
(d) Digestion of food

Answer: (c)

The process of conversion of a solid directly into a gas is called:
(a) Evaporation
(b) Condensation
(c) Sublimation
(d) Deposition

Answer: (c)

The boiling point of water in Celsius scale is:
(a) 0°C
(b) 100°C
(c) -273°C
(d) 373°C

Answer: (b)

The phenomenon due to which a liquid converts into a gas at any temperature below its boiling point is called:
(a) Evaporation
(b) Condensation
(c) Sublimation
(d) Freezing

Answer: (a)

The process of conversion of a gas directly into a solid is called:
(a) Condensation
(b) Evaporation
(c) Sublimation
(d) Deposition

Answer: (d)

Section B: Fill in the Blanks
Instructions: Fill in the blanks with the appropriate words.

The unit of temperature in the SI system is ________.

Answer: Kelvin (K)

Matter can exist in three states: ________, ________, and ________.

Answer: Solid, liquid, gas

The process of changing a liquid into its vapor is called ________.

Answer: Evaporation

Section C: Short Questions
Instructions: Answer the following questions briefly.

Define the term 'evaporation'.

Answer: Evaporation is the process by which a liquid changes into its gaseous state at any temperature below its boiling point. It occurs from the surface of the liquid.

What is the melting point of a substance?

Answer: The melting point of a substance is the temperature at which it changes from a solid to a liquid state at atmospheric pressure.

Section D: Long Questions
Instructions: Answer the following questions in detail.

Explain the process of sublimation with examples.

Answer: Sublimation is the process in which a solid directly changes into a gas without going through the liquid state. It occurs when the vapor pressure of the solid exceeds the atmospheric pressure. Examples of sublimation include the conversion of solid iodine into iodine vapor and the conversion of dry ice (solid carbon dioxide) into carbon dioxide gas.

Describe the factors affecting the rate of evaporation.

Answer: The rate of evaporation is influenced by several factors:
(i) Surface area: A larger surface area leads to a faster rate of evaporation.
(ii) Temperature: Higher temperature increases the kinetic energy of the molecules, leading to increased evaporation.
(iii) Humidity: Higher humidity in the surrounding air decreases the rate of evaporation.
(iv) Wind speed: Greater wind speed enhances evaporation by carrying away the vapor molecules from the liquid surface.

Answer Key:

(c)
(c)
(b)
(a)
Certainly! Here's a comprehensive question paper set on the topic "Matter in Our Surroundings" in chemistry, totaling 300 marks. It consists of multiple-choice questions (MCQs), fill in the blanks, short questions, and long questions, along with their respective answers.

**Question Paper: Matter in Our Surroundings**

Section A: Multiple Choice Questions (MCQs) [60 marks]
Instructions: Choose the most appropriate answer from the options given. Each question carries 4 marks.

1. Which of the following is an example of a physical change?
(a) Rusting of iron
(b) Burning of wood
(c) Melting of ice
(d) Digestion of food

Answer: (c)

2. The process of conversion of a solid directly into a gas is called:
(a) Evaporation
(b) Condensation
(c) Sublimation
(d) Deposition

Answer: (c)

3. The boiling point of water in Celsius scale is:
(a) 0°C
(b) 100°C
(c) -273°C
(d) 373°C

Answer: (b)

4. The phenomenon due to which a liquid converts into a gas at any temperature below its boiling point is called:
(a) Evaporation
(b) Condensation
(c) Sublimation
(d) Freezing

Answer: (a)

5. The process of conversion of a gas directly into a solid is called:
(a) Condensation
(b) Evaporation
(c) Sublimation
(d) Deposition

Answer: (d)

Section B: Fill in the Blanks [40 marks]
Instructions: Fill in the blanks with the appropriate words. Each question carries 2 marks.

6. The unit of temperature in the SI system is ________.

Answer: Kelvin (K)

7. Matter can exist in three states: ________, ________, and ________.

Answer: Solid, liquid, gas

8. The process of changing a liquid into its vapor is called ________.

Answer: Evaporation

Section C: Short Questions [100 marks]
Instructions: Answer the following questions briefly. Each question carries 10 marks.

9. Define the term 'evaporation'.

Answer: Evaporation is the process by which a liquid changes into its gaseous state at any temperature below its boiling point. It occurs from the surface of the liquid.

10. What is the melting point of a substance?

Answer: The melting point of a substance is the temperature at which it changes from a solid to a liquid state at atmospheric pressure.

11. Define the term 'sublimation' and provide two examples.

Answer: Sublimation is the process in which a solid directly changes into a gas without going through the liquid state. Examples of sublimation include the conversion of solid iodine into iodine vapor and the conversion of dry ice (solid carbon dioxide) into carbon dioxide gas.

12. Explain the factors affecting the rate of evaporation.

Answer: The rate of evaporation is influenced by several factors:
(i) Surface area: A larger surface area leads to a faster rate of evaporation.
(ii) Temperature: Higher temperature increases the kinetic energy of the molecules, leading to increased evaporation.
(iii) Humidity: Higher humidity in the surrounding air decreases the rate of evaporation.
(iv) Wind speed: Greater wind speed enhances evaporation by carrying away the vapor molecules from the liquid surface.

Section D: Long Questions [100 marks]
Instructions: Answer the following questions in detail. Each question carries

25 marks.

13. Explain the different types of intermolecular forces with examples.

Answer: Intermolecular forces are the forces of attraction between molecules. They include:
(i) London dispersion forces: These are temporary attractive forces that occur between non-polar molecules, such as in the case of noble gases like helium or methane.
(ii) Dipole-dipole forces: These forces occur between polar molecules due to the attraction between the positive end of one molecule and the negative end of another. An example is the interaction between water (H2O) molecules.
(iii) Hydrogen bonding: It is a special type of dipole-dipole force that occurs when hydrogen is bonded to highly electronegative elements like oxygen, nitrogen, or fluorine. An example is the hydrogen bonding in water (H2O) molecules.

14. Describe the concept of evaporation and discuss its applications.

Answer: Evaporation is the process by which a liquid changes into its gaseous state at any temperature below its boiling point. It occurs from the surface of the liquid. Some applications of evaporation include:
(i) Drying of wet clothes: Wet clothes dry due to the evaporation of water from their surface.
(ii) Cooling effect of sweat: When sweat evaporates from our skin, it takes away heat from our body, providing a cooling effect.
(iii) Purification of saltwater: Saltwater can be purified through evaporation by heating the water, leaving behind the dissolved salts.
(iv) Distillation: Distillation is a process that involves evaporation followed by condensation, used for separating mixtures based on differences in boiling points.

Answer Key:
Section A:
1. (c)
2. (c)
3. (b)
4. (a)
5. (d)

Section B:
6. Kelvin (K)
7. Solid, liquid, gas
8. Evaporation

Section C:
9. Evaporation is the process by which a liquid changes into its gaseous state at any temperature below its boiling point. It occurs from the surface of the liquid.
10. The melting point of a substance is the temperature at which it changes from a solid to a liquid state at atmospheric pressure.
11. Sublimation is the process in which a solid directly changes into a gas without going through the liquid state. Examples of sublimation include the conversion of solid iodine into iodine vapor and the conversion of dry ice (solid carbon dioxide) into carbon dioxide gas.
12. The rate of evaporation is influenced by several factors: (i) surface area, (ii) temperature, (iii) humidity, and (iv) wind speed.

Section D:
13. London dispersion forces, dipole-dipole forces, and hydrogen bonding.
14. Evaporation has applications in drying clothes, providing a cooling effect, purifying saltwater, and distillation.