Chapter 5: Substances in the Surroundings –Their States and Properties
Solved textbook questions with step-by-step explanations.
Grade 6 Q&A: Chapter 5: Substances in the Surroundings - Their States and Properties
Welcome to the Questions and Answers section for Grade 6 Environmental Studies (Part One), Chapter 5: "Substances in the Surroundings - Their States and Properties." This chapter introduces us to the fundamental concept of matter and its three common states: solid, liquid, and gas. We will explore the unique properties of each state, understand how substances change from one state to another, and learn about the role of temperature in these transformations.
Important Questions and Answers
Q1: What is a substance?
Answer: A substance is a form of matter that has a uniform and definite composition and distinct properties.
Q2: Name the three common states of matter.
Answer: The three common states of matter are solid, liquid, and gas.
Q3: What are the properties of a solid? Give an example.
Answer: A solid has a definite shape and a definite volume. Its particles are tightly packed. Example: A stone, a block of wood, ice.
Q4: What are the properties of a liquid? Give an example.
Answer: A liquid has a definite volume but no definite shape; it takes the shape of its container. Its particles are less tightly packed than solids. Example: Water, milk, oil.
Q5: What are the properties of a gas? Give an example.
Answer: A gas has neither a definite shape nor a definite volume; it fills the entire space available to it. Its particles are very loosely packed and move freely. Example: Air, oxygen, steam.
Q6: What is melting? Give an example.
Answer: Melting is the process by which a solid changes into a liquid upon heating. Example: Ice melting into water.
Q7: What is freezing? Give an example.
Answer: Freezing is the process by which a liquid changes into a solid upon cooling. Example: Water freezing into ice.
Q8: What is evaporation? Give an example.
Answer: Evaporation is the process by which a liquid changes into a gas (vapor) at any temperature below its boiling point. Example: Water drying from clothes, formation of clouds.
Q9: What is boiling?
Answer: Boiling is the process by which a liquid changes rapidly into a gas (vapor) at a specific temperature called its boiling point, with bubbles forming throughout the liquid.
Q10: What is condensation? Give an example.
Answer: Condensation is the process by which a gas (vapor) changes into a liquid upon cooling. Example: Water droplets forming on a cold glass, formation of dew.
Q11: What is sublimation? Give an example.
Answer: Sublimation is the process by which a solid changes directly into a gas without passing through the liquid state. Example: Dry ice (solid carbon dioxide) changing into gas, camphor disappearing.
Q12: How does temperature affect the state of a substance?
Answer: Temperature affects the state of a substance by influencing the energy and arrangement of its particles. Heating can cause solids to melt into liquids and liquids to evaporate into gases, while cooling can cause gases to condense into liquids and liquids to freeze into solids.
Q13: What is the boiling point of water?
Answer: The boiling point of water is 100°C (212°F) at standard atmospheric pressure.
Q14: What is the freezing point of water?
Answer: The freezing point of water is 0°C (32°F).
Q15: What is the difference between evaporation and boiling?
Answer: Evaporation occurs at any temperature below the boiling point and only from the surface of the liquid, while boiling occurs at a specific boiling point and involves the formation of bubbles throughout the liquid.
Q16: Why do clothes dry faster on a windy day?
Answer: Clothes dry faster on a windy day because the wind carries away the water vapor formed during evaporation, preventing the air around the clothes from becoming saturated with moisture, thus allowing more water to evaporate.
Q17: Why does water stored in an earthen pot (matka) stay cool?
Answer: Water in an earthen pot stays cool due to evaporation. The porous surface of the pot allows a small amount of water to seep out and evaporate, taking latent heat from the remaining water and thus cooling it.
Q18: What is a solution? Give an example.
Answer: A solution is a homogeneous mixture of two or more substances, where one substance (solute) dissolves completely in another (solvent). Example: Salt dissolved in water, sugar dissolved in water.
Q19: What is solubility?
Answer: Solubility is the maximum amount of a solute that can dissolve in a given amount of solvent at a specific temperature to form a saturated solution.
Q20: Why do some substances dissolve in water while others do not?
Answer: Substances dissolve in water if their particles can mix uniformly with water particles due to similar intermolecular forces. Substances like oil do not dissolve because their particles do not interact well with water particles.
Q21: What are physical properties of substances? Give examples.
Answer: Physical properties are characteristics of a substance that can be observed or measured without changing the substance's chemical composition. Examples include color, shape, size, state (solid, liquid, gas), melting point, boiling point, and density.
Q22: What are chemical properties of substances?
Answer: Chemical properties describe how a substance reacts with other substances or changes its chemical composition. Examples include flammability (how easily it burns) and reactivity with acids or bases.
Q23: How can we separate insoluble substances from water?
Answer: Insoluble substances can be separated from water by methods like filtration (e.g., separating sand from water) or decantation (allowing solids to settle and pouring off the liquid).
Q24: What is the effect of heat on the particles of a substance?
Answer: When a substance is heated, its particles gain energy and move more vigorously. In solids, they vibrate more; in liquids, they move more freely; and in gases, they move very rapidly, leading to changes in state.
Q25: Why is water called a 'universal solvent'?
Answer: Water is called a 'universal solvent' because it can dissolve a large number of different substances, more than any other liquid, due to its polar nature.
Q26: What is a mixture? Give an example.
Answer: A mixture is a substance containing two or more different substances that are not chemically bonded together. Example: Air (mixture of gases), salt and sand mixture.
Q27: What is the difference between a homogeneous and a heterogeneous mixture?
Answer: In a homogeneous mixture (like a solution), the components are uniformly distributed and cannot be easily distinguished. In a heterogeneous mixture (like sand and water), the components are not uniformly distributed and can be easily seen separately.
Exercise Solutions
Q1: Fill in the blanks.
- A solid has a definite shape and volume.
- A liquid has a definite volume but no definite shape.
- A gas has neither a definite shape nor a definite volume.
- The process of a solid changing directly into a gas is called sublimation.
- Water is called a universal solvent.
Q2: Match the pairs.
(Note: As an AI, I cannot create interactive matching. I will provide the correct pairs.)
- Ice - Solid
- Water - Liquid
- Steam - Gas
- Melting - Solid to Liquid
- Evaporation - Liquid to Gas
Q3: True or False.
- Particles in a solid are tightly packed. True
- Liquids have a definite shape. False
- Gases can be compressed easily. True
- Condensation is the change of gas to liquid. True
- Salt does not dissolve in water. False
Q4: Answer the following questions.
- What are the three states of matter? Explain with examples.
Answer: The three states of matter are:- Solid: Has definite shape and volume (e.g., stone, ice).
- Liquid: Has definite volume but no definite shape (e.g., water, milk).
- Gas: Has neither definite shape nor volume (e.g., air, steam).
- What is the difference between melting and freezing?
Answer: Melting is the process where a solid changes into a liquid upon heating, while freezing is the reverse process where a liquid changes into a solid upon cooling. - Why do clothes dry faster in the sun?
Answer: Clothes dry faster in the sun because the heat from the sun increases the rate of evaporation of water from the clothes, converting it into water vapor more quickly. - What is a solution? Give an example.
Answer: A solution is a homogeneous mixture where one substance (solute) dissolves completely in another (solvent). Example: Sugar dissolved in water.
Q5: Give reasons.
- Water is called a universal solvent.
Reason: Water is called a universal solvent because it has the ability to dissolve a wide variety of substances, more than any other liquid, due to its polar molecular structure. - Gases do not have a definite shape or volume.
Reason: Gases do not have a definite shape or volume because their particles are very far apart and move randomly and rapidly, occupying the entire space of the container they are in. - It is important to know the properties of substances.
Reason: It is important to know the properties of substances because this knowledge helps us understand how they behave, how they can be used, how to store them safely, and how they interact with other substances in various applications and processes.
References
- Maharashtra State Board Environmental Studies (Part One) Standard Six Textbook (2015 Edition) - Chapter 5: Substances in the Surroundings - Their States and Properties.
- Maharashtra State Board 6th Standard Environmental Studies Syllabus.
- Balbharati Environmental Studies Part 1 Textbook.