A. Choose the correct option.
1. Which of the following is true about atoms and molecules
a. They are very small. b. They are always in motion. C. They exert force on each other. D. All of these
Answer. D. All of these
2. What of the following is true about the features of particles of matter?
a. Very small particles always at rest, have space between them, and exert force on each other.
b. Very small, particles always at rest, have space in between them, and do not exert force on each other.
c. Very small particles, always in motion have space in between them, and do not exert force on each other.
d. Very small particles, always in motion have space in between them, and do not exert force on each other.
Answer. c. Very small, always moving, space between, exert force.
Q3. Which of the following can be used to determine whether a given substance is a solid, liquid or gas?
- Volume and area. b. Shape and length. C. Volume and shape. d. Shape and area.
Answer. c. Volume and shape
Q4. Which of the following states of matter has fixed volume and a fixed shape?
- Solid. b. liquid. C. Gas. d. All of these.
Answer. a. Solid
Q5. Which of the following states of matter can flow freely in every direction?
- Solid. b. liquid. C. Gas. d. All of these.
Answer. C. Gas
- Assertion and Reason question.
Q1. Assertion (A): Air is an example of matter.
Reason (R): Anything that has mass and occupies space is called matter.
- Both A and R are true. b. Both A and R are false. c. A is true and R is true. d. A is false and R is true.
Answer: a. Both A and R are true.
Air is matter because it has mass and fills space.
Q2. Question:
Assertion (A): Solids cannot be compressed.
Reason (R): The particles in a solid are loosely packed.
- Both A and R are true. b. Both A and R are false. c. A is true and R is true. d. A is false and R is true.
Answer: c. A is True and R is False
– Correction for R: The particles in a solid are tightly packed, not loosely packed.
c. True/False Statements
1. Anything that has mass and occupies space is called matter, not just a solid.
Answer. False
2. Gas particles move freely and do not have a fixed position.
Answer. False
3. Solid particles are arranged very close together.
Answer .True
4. Particles in liquids vibrate and slide over one another.
Answer. True
5. Gases are easy to compress, not difficult.
Answer. False
D. Match the Following
| Column A | Column B |
| Matter is composed of these | Solids |
| These take the shape of the container | b.Gases |
| These have the strongest inter-particle attraction | c.Powder |
| These have the greatest inter-particle distance | d. Particles |
| This form of solid can appear to flow like a liquid | e. Liquids |
1. d. Particles
2. e. Liquids
3. a. Solids
4. b. Gases
5. c. Powder
E. Give Reasons for the following.
Q1.Milk takes the shape of the glass it is poured into
Answer. This property is not unique to milk; water, juice, and other liquids exhibit similar behavior. It’s why liquids are stored in bottles, glasses, or jars rather than left open. The ability to flow makes liquids easy to pour and transfer.
Milk takes the shape of its container because of its liquid state, where molecules move freely and adjust to the vessel’s structure. This fundamental property of liquids is essential in daily life, from drinking beverages to storing liquids in industrial settings.
Q2. Containers without solids or liquids are not empty
Answer. At first glance, a container with no visible solids or liquids may seem empty, but in reality, it is filled with air and other gaseous substances. Even in what we consider a “vacuum,” traces of particles or energy may still exist. Here’s why:
Presence of Air (Gases)
- Air is a mixture of gases (mainly nitrogen, oxygen, carbon dioxide, and argon) that fills any “empty” space.
- When you pour out a liquid or remove a solid, air rushes in to occupy the space due to atmospheric pressure.
- This is why a “sealed empty” bottle still contains air unless deliberately vacuum-sealed.
Q3. A table has a fixed shape and volume –
Answer. A table, like most solid objects, maintains a fixed shape and volume due to the strong molecular bonds and rigid structure of its material. Unlike liquids and gases, solids resist changes in form because their particles are tightly packed and held in place. Here’s a detailed explanation:
Strong Intermolecular Forces
- Solids, such as wood or metal (common table materials), have molecules arranged in a fixed, ordered pattern.
- These molecules are held together by powerful forces (ionic, covalent, or metallic bonds), preventing them from moving freely.
- This rigidity ensures the table retains its shape unless an external force (like cutting or breaking) is applied.
- . Definite Volume Retention
- Unlike liquids and gases, solids do not compress or expand easily under normal conditions.
- Their particles vibrate in place but do not shift positions, maintaining a constant volume.
- Crystalline or Amorphous Structure
- Crystalline solids (e.g., metal tables) have a repeating geometric pattern, contributing to their stability.
- Amorphous solids (e.g., plastic tables) lack a defined pattern but still resist deformation due to tightly packed molecules.
- External Factors and Exceptions
- Extreme conditions (e.g., high heat or pressure) can alter a solid’s shape (e.g., melting metal).
- However, under everyday conditions, solids like tables remain unchanged.
Q4. We can smell incense from a distance.
Answer. The ability to smell incense even from a distance is due to the diffusion of aromatic particles through the air. This phenomenon occurs because of the following scientific principles:
1. Evaporation & Sublimation of Incense Particles
- When incense burns, it releases fragrant smoke containing volatile organic compounds (VOCs).
- These compounds evaporate (from liquid to gas) or sublimate (from solid directly to gas) into the air, becoming airborne.
2. Diffusion & Brownian Motion
- The incense particles spread out (diffusion) due to the natural movement of air molecules.
- Brownian motion (random movement of microscopic particles in a fluid) helps disperse the scent molecules evenly.
3. Air Currents & Wind Assistance
- Even in still air, convection currents (warm air rising) carry the fragrance upward and outward.
- Breezes or wind further accelerate the spread, allowing the scent to travel long distances.
4. Sensitivity of the Human Nose
- The human olfactory system is highly sensitive to certain aromatic compounds.
- Even trace amounts of incense molecules in the air can trigger smell receptors in our nose.
5. Low Molecular Weight of Fragrance Compounds
- Many incense scents come from lightweight molecules (like terpenes and esters), which travel easily through air.
Q5. Gas needs a closed container, but liquid does not –
Answer.
The difference in how gases and liquids behave when stored comes down to their molecular structure, intermolecular forces, and ability to flow. Here’s why gases require a sealed container, while liquids can often remain in open vessels:
1. Molecular Behavior & Freedom of Movement
- Gases have molecules that are far apart, move rapidly, and have weak intermolecular forces. This allows them to expand indefinitely and escape if not confined.
- Liquids have molecules that are closer together, with stronger cohesive forces (like surface tension), keeping them in a fixed volume unless acted upon.
2. Compressibility & Expansion
- Gases are highly compressible and will fill any available space. Without a closed container, they disperse into the atmosphere.
- Liquids are nearly incompressible and maintain a fixed volume, staying in an open container unless spilled or evaporated.
3. Evaporation vs. Diffusion
- A liquid in an open container may evaporate slowly, but most of it remains in place due to gravity and surface tension.
- A gas, however, diffuses rapidly into the air, mixing completely and escaping if not enclosed.
4. Pressure & Containment Requirements
- Gases exert pressure on container walls due to constant molecular collisions. A sealed container prevents them from escaping.
- Liquids exert pressure mostly downward (hydrostatic pressure), so they don’t require a lid unless preventing spills or evaporation is necessary.
Real-Life Applications
- Gas Storage: LPG cylinders, oxygen tanks, and aerosol cans must be sealed to prevent leaks.
- Liquid Storage: Water in a glass or fuel in an open drum (though covers prevent contamination)
Q6. Gases can be compressed easily. Answer. Gases can be compressed easily because gas particles have large spaces between them.
Answer.
Gases can be compressed much more easily than solids or liquids because their molecules are far apart and weakly bonded, allowing them to be pushed closer together under pressure. Here’s a detailed explanation:
1. Large Intermolecular Spaces
- Gas particles are separated by large empty spaces compared to solids and liquids.
- When pressure is applied (e.g., in a piston or gas cylinder), these gaps reduce, forcing molecules into a smaller volume.
2. Weak Intermolecular Forces
- Unlike solids (rigid bonds) or liquids (moderate cohesion), gas molecules have negligible attractive forces between them.
- This lack of resistance allows them to be squeezed together without requiring extreme force.
3. High Kinetic Energy & Free Movement
- Gas particles move rapidly in random directions, colliding with container walls.
- When compressed, their speed increases (raising temperature), but their volume decreases significantly.
4. Compressibility vs. Incompressibility of Other States
- Solids resist compression because their tightly packed atoms repel each other.
- Liquids are nearly incompressible due to moderate molecular spacing.
- Gases, however, can be compressed to fractions of their original volume (e.g., LPG in tanks).
5. Practical Applications
- Fuel Storage: Compressed natural gas (CNG) is stored at high pressure for transport.
- Industrial Uses: Pneumatic tools and refrigeration rely on gas compression.
Exceptions & Limits
- At extremely high pressures, gases may liquefy (e.g., CO₂ in fire extinguishers).
- Ideal gases follow Boyle’s Law (Pressure ∝ 1/Volume), but real gases deviate slightly.
F. Short Answer Questions
Q1. Name three states of matter. Give two examples of each.
Answer.
The Three States of Matter with Examples
Matter exists in three primary states: solid, liquid, and gas. Each state has distinct properties based on the arrangement and movement of its particles. Below is a detailed explanation along with two common examples of each state.
1. Solids
Solids have a fixed shape and volume because their particles are tightly packed in a rigid structure. The molecules vibrate in place but do not move freely.
Examples of Solids:
- Ice – Frozen water (H₂O) where molecules form a crystalline lattice.
- Wood – A rigid natural material composed of tightly bound cellulose fibers.
Key Properties:
- High density
- Definite shape and volume
- Cannot flow
2. Liquids
Liquids have a fixed volume but no fixed shape, taking the form of their container. Their particles are close but can slide past one another, allowing flow.
Examples of Liquids:
- Water – A universal solvent that adapts to any container.
- Mercury – A dense, metallic liquid used in thermometers.
Key Properties:
- Moderate density
- Takes container’s shape
- Can flow and be poured
3. Gases
Gases have no fixed shape or volume, expanding to fill any space. Their particles move rapidly and are far apart.
Examples of Gases:
- Oxygen (O₂) – Essential for respiration, found in the atmosphere.
- Carbon Dioxide (CO₂) – Exhaled by humans and used in fizzy drinks.
Key Properties:
- Low density
- Highly compressible
- Diffuses easily
Why Do These States Exist?
The state of matter depends on temperature and pressure:
- Cooling a gas (e.g., steam → water → ice) decreases particle energy, changing its state.
- Heating a solid (e.g., ice → water → vapor) provides energy to break molecular bonds.
Real-World Applications
- Solids → Construction (bricks, metals).
- Liquids → Hydraulics (oil, blood circulation).
- Gases → Fuel (propane), medical oxygen.
Q2. Explain the Difference between the arrangement of particles in liquids and gases with the help of diagrams.
Answer. Liquids: Particles are close but can slide past each other.
Gases: Particles are far apart and move freely.
Q3. Why do Gases expand to fill the container, whereas liquids do not
Answer.
The fundamental difference in behavior between gases and liquids when placed in a container stems from their molecular structure and intermolecular forces. Here’s why gases expand completely while liquids maintain a fixed volume:
1. Molecular Spacing & Movement
- Gases: Particles are far apart with weak intermolecular forces, allowing them to move freely in all directions. They collide with container walls, creating pressure that makes them uniformly fill the entire space.
- Liquids: Particles are closer together with stronger cohesive forces (e.g., hydrogen bonds in water). They can flow but remain bound to neighboring molecules, forming a distinct surface.
2. Kinetic Energy & Pressure
- Gases: High kinetic energy enables particles to overcome gravitational pull and disperse evenly. They exert pressure equally in all directions, forcing expansion.
- Liquids: Lower kinetic energy keeps particles constrained by gravity and surface tension, causing them to settle at the bottom.
3. Compressibility
- Gases: Highly compressible due to empty space between particles. They adapt to any container volume.
- Liquids: Nearly incompressible; their volume stays constant regardless of container shape.
Real-World Example
- A balloon inflates (gas expansion) vs. water taking a glass’s shape (liquid adaptation).
Q4.Reema’s mother took a tall, thin glass and a flat cup and poured 200 ml of hot Chocolate into each. Reema took the tall, thin glass, thinking that it had more chocolate in each. Reema took a thin glass, thinking that it had more chocolate than the other. Which property of liquid is she missing here?
Answer:
Reema’s confusion stems from overlooking the volume of the liquid and focusing instead on its height in the container. This misconception arises because liquids adapt to the shape of their container, creating an optical illusion. Here’s a detailed explanation:
1. The Property She Missed: Liquid Takes the Shape of Its Container
Liquids have no fixed shape but a fixed volume. When poured into different containers:
- Tall, Thin Glass: The chocolate rises to a greater height, making it appear like more.
- Flat, Wide Cup: The same volume spreads out, looking shallower.
Reema assumed “more height = more quantity,” ignoring that both glasses held 200 ml—the same amount, just distributed differently.
2. Why This Happens: The Science of Liquid Behavior
- Surface Tension & Gravity: Liquids settle based on gravity, forming a flat surface regardless of container shape.
- Volume Conservation: Unlike gases, liquids cannot compress or expand, so their quantity remains constant.
3. Real-Life Examples
- Pouring Water: A liter of water looks different in a vase vs. a bowl but is the same amount.
- Cooking Measurements: 250 ml of oil fills a measuring cup to a certain mark, no matter the cup’s width.
How to Avoid This Mistake
- Use Measuring Tools: A scale or graduated container confirms volume.
- Compare Cross-Sections: A wide cup may need less height to hold the same volume as a narrow glass.
G. Long Answer Questions
Q1. Compare and contrast properties of solids, liquids, and gases:
Answer.
Matter exists in three primary states—solids, liquids, and gases—each with distinct characteristics based on molecular arrangement and energy. Understanding their properties helps explain everyday phenomena, from ice melting to steam rising. Below is a detailed comparison:
1. Molecular Structure & Movement
- Solids:
- Particles: Tightly packed in a fixed, orderly arrangement (crystalline) or irregular (amorphous).
- Movement: Vibrate in place but cannot move freely.
- Example: Iron (crystalline), glass (amorphous).
- Liquids:
- Particles: Close together but not rigid; can slide past one another.
- Movement: Flow freely, allowing liquids to adapt to container shapes.
- Example: Water, oil.
- Gases:
- Particles: Far apart with weak or no intermolecular bonds.
- Movement: Move rapidly and randomly, colliding with surfaces.
- Example: Oxygen, carbon dioxide.
2. Shape and Volume
- Solids:
- Fixed shape and volume (e.g., a wooden block stays the same unless cut).
- Liquids:
- Fixed volume but no fixed shape (e.g., water takes the shape of a cup but fills only 200 ml).
- Gases:
- No fixed shape or volume (e.g., perfume spreads to fill a room).
3. Compressibility
- Solids:
- Nearly incompressible due to dense particle packing.
- Liquids:
- Slightly compressible under extreme pressure (e.g., deep-ocean water).
- Gases:
- Highly compressible (e.g., LPG gas stored in small cylinders).
4. Density & Energy
- Solids:
- High density (particles packed closely).
- Low kinetic energy (particles vibrate minimally).
- Liquids:
- Moderate density (less dense than solids but denser than gases).
- Moderate energy (particles move but stay cohesive).
- Gases:
- Low density (large empty spaces between particles).
- High kinetic energy (particles move rapidly).
5. Real-World Applications
- Solids: Used in construction (bricks), tools (metals), and everyday objects (furniture).
- Liquids: Essential for hydration (water), lubrication (oil), and transport (fuel).
- Gases: Critical for breathing (oxygen), cooking (natural gas), and refrigeration (coolants).
Q2. Sugar can be made to flow from one tumbler to another. Do you think it is liquid? Explain the answer
Answer.
At first glance, sugar seems to behave like a liquid when you pour it from one container to another—it flows smoothly, takes the shape of its new container, and forms a pile at the bottom. But does this mean sugar is a liquid? The answer is no, and here’s why:
1. The Definition of Liquids vs. Solids
To determine whether sugar is a liquid, we need to understand the key properties of liquids and solids:
- Liquids:
- Have no fixed shape but a fixed volume.
- Molecules slide past each other, allowing flow.
- Adapt to the shape of their container (e.g., water in a glass).
- Solids:
- Have fixed shape and volume under normal conditions.
- Molecules vibrate in place but do not flow freely.
- Resist deformation unless broken or melted (e.g., ice, metal).
Sugar, in its granulated form, is a solid—but it can still flow under certain conditions.
2. Why Does Sugar Flow Like a Liquid?
The ability of sugar to pour doesn’t make it a liquid. Instead, this behavior is due to:
A. Granular Nature (Flowable Solid)
- Sugar consists of tiny, dry crystals that can move past each other when poured.
- This is similar to sand or salt—they flow but are still solids.
B. Gravity and Particle Movement
- When you tilt a sugar jar, gravity causes the grains to slide over one another, creating a flowing effect.
- Unlike liquids, sugar grains do not change shape or merge—they remain individual particles.
C. Angle of Repose (Pile Formation)
- When poured, sugar forms a pile due to friction between grains.
- Liquids, on the other hand, spread out to form a flat surface (unless viscous like honey).
3. Key Differences Between Sugar and True Liquids
| Property | Sugar (Solid Granules) | Liquid (e.g., Water) |
|---|---|---|
| Shape | Takes shape when poured but retains grain structure | Takes exact container shape |
| Volume | Fixed (does not compress) | Fixed (but adapts to container) |
| Molecular Movement | Particles slide but don’t flow freely | Molecules move and mix freely |
| Surface Behavior | Forms a pile when poured | Forms a flat surface |
4. Real-World Examples of Flowable Solids
- Sand in an hourglass – Flows but is solid.
- Flour in a bag – Pours but doesn’t behave like water.
- Rice or grains – Can be poured but remain solid.
These materials are called granular solids—they mimic liquid flow but are structurally rigid.
5. When Does Sugar Actually Become a Liquid?
Sugar only turns into a liquid when melted at high temperatures (e.g., making caramel). In this state:
- The rigid crystal structure breaks down.
- Molecules move freely like a true liquid.
- It takes the shape of its container without forming grains.
At room temperature, however, sugar remains a free-flowing solid.
Q3. What would happen to the properties of particles of matter if Water is frozen to ice?
Answer. The particles change from loosely packed liquid to tightly packed solid, losing the ability to flow.
Q4. Table Completion:
| Object | Define Volume | Definite shape | Needs a container | Can be cut | Flows easily |
| Honey | |||||
| Helium | Yes | ||||
| Paper |
Answer.
| Object | Define Volume | Definite shape | Needs a container | Can be cut | Flows easily |
| Honey | Yes | No | yes | No | Yes |
| Helium | No | No | Yes | NO | Yes |
| Paper | yes | Yes | No | Yes | NO |