Matter In Our Surroundings - Class 9 Science - Chapter 1 - Notes, NCERT Solutions & Extra Questions
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Notes - Matter In Our Surroundings | Class 9 NCERT | Science
This comprehensive guide will help students grasp essential concepts, definitions, properties, and classifications of matter, as prescribed in the curriculum.
What is Matter?
Matter is anything in the universe that occupies space and has mass. It can exist in various shapes, sizes, and textures. For instance, the air we breathe, the food we eat, stones, clouds, stars, plants, animals, and even a small particle of sand are all matter. Each of these entities occupies space and has mass, thus fulfilling the criteria for being classified as matter.
Classification of Matter
Early Indian philosophers categorized matter into five basic elements: air, earth, fire, sky, and water, known as the "Panch Tatva." Modern science further classified matter based on its physical and chemical properties. This chapter focuses on the physical properties of matter, leaving chemical aspects for subsequent chapters.
Physical Nature of Matter
Matter is Made Up of Particles
For a long time, scientists debated whether matter was continuous or made up of particles. Experiments using salt in water demonstrated that matter is indeed composed of particles. When salt dissolves in water, it disperses into the spaces between the water particles, affirming the particulate nature of matter.
How Small Are These Particles?
Particles of matter are exceptionally small, far beyond our imagination. Experiments using potassium permanganate crystals illustrate that even tiny amounts can color a large volume of water due to the countless particles breaking into smaller units.
Characteristics of Particles in Matter
Space Between Particles
Experiments with salt, sugar, or even scents show that particles of different substances blend through spaces between each other, highlighting the existence of gaps between the particles of matter.
Movement of Particles
Particles in matter are always in motion, a phenomenon known as kinetic energy. This movement increases with temperature, accelerating diffusion—the intermixing of particles across different types of matter.
Attraction Between Particles
Different substances exhibit varied degrees of attraction between their particles. For instance, the force of attraction is stronger in solids compared to liquids and gases.
States of Matter
The Solid State
Solids have a definite shape, distinct boundaries, and fixed volumes. They demonstrate rigidity, maintaining their shape under force. Examples include pen, book, needle, and wooden stick.
The Liquid State
Liquids lack a fixed shape but have definite volumes. They flow easily, taking the shape of their containers. Common examples are water, oil, milk, and juice.
The Gaseous State
Gases do not have a fixed shape or volume. They expand to fill their containers, are highly compressible, and diffuse quickly into other gases. Examples include the air we breathe and gases in balloons.
How Matter Can Change its State
Effect of Temperature
Increasing the temperature can transform solids into liquids (melting) and liquids into gases (vaporization). This transformation involves energy exchange known as latent heat, which doesn't increase the substance’s temperature during the phase change.
Effect of Pressure
Applying pressure can convert gases into liquids and solids. For example, solid carbon dioxide (dry ice) transforms directly into gas under reduced pressure, demonstrating sublimation.
Sublimation and Deposition
Sublimation is the direct transition from solid to gas without passing through the liquid state, while deposition is the reverse process. Camphor and dry ice are examples of substances undergoing sublimation.
Evaporation and Cooling
Evaporation is a surface phenomenon where particles at the liquid surface convert into vapor at temperatures below boiling points. Factors affecting evaporation include surface area, temperature, humidity, and wind speed. For example, wet clothes dry faster when spread out (increased surface area) and on windy days (increased wind speed).
Conservation of Mass in Matter
The law of conservation of mass states that mass can neither be created nor destroyed in chemical reactions. This principle applies to matter in all its forms and helps explain how matter remains constant during physical and chemical changes.
Conclusion
Understanding "Matter in Our Surroundings" equips students with foundational knowledge about the physical properties, states, and behaviors of matter. This knowledge is crucial for grasping more advanced scientific concepts and appreciating the natural world.
By focusing on these structured notes, students can enhance their understanding and performance in Class 9 Science.
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Extra Questions - Matter In Our Surroundings | NCERT | Science | Class 9
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Ask Chatterbot AIUnderstanding Matter: What Is Matter Made Of? - Matter In Our Surroundings | Class 9 NCERT | Science
Have you ever wondered what everything around you is made of? From the air you breathe to the food you eat, everything is constructed from "matter." Matter is anything that has mass and occupies space. But what exactly is matter made of? Let’s delve into this fascinating topic and get a clearer picture of the building blocks of our universe.
What Is Matter?
Matter is composed of atoms and molecules, which are too tiny to be seen with the naked eye. These fundamental particles come together in various ways to form the substances and objects we interact with daily. The study of matter takes us through the universally fascinating fields of physics and chemistry.
Historical Perspective
Ancient Indian philosophers had a unique take on matter, describing it as composed of five basic elements: air, earth, fire, water, and sky. Similarly, ancient Greek philosophers like Empedocles and Aristotle posited four elements – earth, water, air, and fire – as the fundamental constituents of matter. Modern science, however, has advanced much beyond these ancient concepts, classifying matter based on its physical and chemical properties.
Physical Nature of Matter
Matter can either be continuous or particulate. The continuous theory posits that matter is a continuous substance, much like a block of wood. On the other hand, the particulate theory, which modern science supports, views matter as consisting of tiny particles.
Experiments Illustrating the Particulate Nature of Matter
Dissolving Salt in Water: By dissolving salt in water, the salt particles spread evenly in the spaces between the water particles, showing that matter is particulate.
Dilution of Potassium Permanganate: A small amount of potassium permanganate can colour a large volume of water, indicating the presence of tiny particles.
Both experiments highlight that matter is composed of particles small beyond our imagination.
Characteristics of Matter’s Particles
Space Between Particles: Particles of matter have spaces between them. This is evident when substances like salt or sugar dissolve in water, occupying the spaces between water particles.
Continuous Movement: Particles of matter are never still. They are in constant motion, possessing kinetic energy. This can be observed when an unlit incense stick emits a smell that spreads throughout a room, or when ink spreads in water without any stirring.
Attraction Between Particles: Particles of matter attract each other. The strength of this attraction varies across different types of matter. For example, the rigid structure of a solid like iron nails indicates a strong attraction, while the flexibility of a rubber band indicates a weaker attraction.
States of Matter
Matter exists in three primary states: solid, liquid, and gas. The state of matter depends on the arrangement, movement, and energy of its particles.
Solids: Solids have a definite shape and volume. Their particles are closely packed in a fixed arrangement, making them rigid. For instance, a book or a piece of wood doesn't change its shape unless acted upon by an external force.
Liquids: Liquids have a fixed volume but no definite shape. They take the shape of their container. The particles are closely packed but not in a fixed position, allowing them to flow. Examples include water, milk, and oil.
Gases: Gases have neither a fixed shape nor a fixed volume. The particles are far apart and move freely, filling any container they are placed in. Examples include air and helium.
Changing States of Matter
Matter can change from one state to another through the processes of melting, freezing, condensation, and evaporation.
Melting: Solid to liquid. For example, ice melting into water.
Freezing: Liquid to solid, such as water freezing into ice.
Evaporation: Liquid to gas, like water turning into steam.
Condensation: Gas to liquid, evident when steam cools to form water droplets.
The Role of Temperature and Pressure
Temperature and pressure play crucial roles in changing the state of matter. Heating a solid increases the kinetic energy of its particles, causing them to move more vigorously and eventually turn into a liquid. Further heating transforms the liquid into a gas. Conversely, cooling a gas brings its particles closer, transforming it back into a liquid and finally into a solid.
Applying pressure can also change the state of matter. For instance, increasing the pressure on a gas can transform it into a liquid, a principle utilised in compressing gases like natural gas for storage.
Sublimation
Some substances can change directly from a solid to a gas without passing through the liquid phase. This process is called sublimation. A common example is dry ice, which is solid carbon dioxide that sublimates directly into gas.
Conclusion
Understanding matter and its properties opens a window to the fascinating nature of our universe. The intricate dance of particles, their mutual attractions, and their transitions through different states are fundamental to the material world around us. The more we learn about matter, the more we uncover the subtle and profound workings of nature.
Whether you're gazing at the stars or simply drinking a glass of water, remember that everything is built from the same tiny, invisible particles. Matter's simplicity and complexity are a testament to the wonders of science, making every ordinary object a point of extraordinary curiosity.
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NCERT Solutions - Matter In Our Surroundings | NCERT | Science | Class 9
Convert the following temperatures to the celsius scale.
(a) $293 \mathrm{~K}$
(b) $470 \mathrm{~K}$
To convert temperatures from the Kelvin scale to the Celsius scale, you can use the following formula:
$$ T(^\circ C) = T(K) - 273.15 $$
Where $ T(^\circ C)$ is the temperature in degrees Celsius and $T(K) $ is the temperature in Kelvin.
Let's use the formula for the given temperatures:
(a) For 293 K:
$$ 293 \mathrm{~K} - 273.15 = 19.85 ^\circ C $$
(b) For 470 K:
$$ 470 \mathrm{~K} - 273.15 = 196.85 ^\circ C $$
So, 293 K is equivalent to 19.85 °C and 470 K is equivalent to 196.85 °C.
Convert the following temperatures to the kelvin scale.
(a) $25^{\circ} \mathrm{C}$
(b) $373^{\circ} \mathrm{C}$
To convert temperatures from Celsius to Kelvin, you can use the following formula:
$$ T(K) = T(^\circ C) + 273.15 $$
where $ T(K) $ is the temperature in kelvins and $ T(^\circ C) $ is the temperature in degrees Celsius.
Let's do the calculations:
(a) $ 25^{\circ} C $ to kelvins:
$$ T(K) = 25 + 273.15 = 298.15 \ \text{K} $$
(b) $ 373^{\circ} C $ to kelvins:
$$ T(K) = 373 + 273.15 = 646.15 \ \text{K} $$
Therefore, $ 25^{\circ} C $ is equal to $ 298.15 \ \text{K} $, and $ 373^{\circ} C $ is equal to $ 646.15 \ \text{K} $.
Give reason for the following observations.
(a) Naphthalene balls disappear with time without leaving any solid.
(b) We can get the smell of perfume sitting several metres away.
The observations you've noted can be explained through the process of sublimation and the diffusion of particles, respectively.
(a) Naphthalene balls disappear with time without leaving any solid: Naphthalene is a substance that undergoes sublimation, which means it can transition directly from a solid state to a gaseous state without going through a liquid phase under standard atmospheric conditions. Over time, as the naphthalene balls are exposed to air, they gradually sublimate, turning into gas molecules that disperse into the air. This is why the balls get smaller and eventually disappear without leaving any solid residue behind.
(b) We can get the smell of perfume sitting several metres away: The smell of perfume is carried to us by the process of diffusion. Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. Perfume consists of volatile compounds that evaporate into the air and become gas particles. Once in gaseous form, these particles spread out and mix with air molecules. As time passes, these fragrant particles can travel over several metres, allowing the smell to be detected far from the original source. This is why you can smell perfume even if you are sitting several metres away.
Arrange the following substances in increasing order of forces of attraction between the particles- water, sugar, oxygen.
In substances, the forces of attraction between the particles influence the physical state and many physical properties of the material, such as melting point, boiling point, and solubility.
Here's how these three substances are arranged by their forces of attraction from weakest to strongest:
Oxygen: As a diatomic molecule $O2$, oxygen is a gas at room temperature, which indicates weaker forces of attraction. The primary intermolecular force present in oxygen is London dispersion forces, which are the weakest type of van der Waals force.
Water: Water $H2O$ is a liquid at room temperature, which means its molecules experience stronger intermolecular attractions than gas particles. The primary type of intermolecular force in water is hydrogen bonding, which is significantly stronger than London dispersion forces.
Sugar: Sugar (sucrose) is a solid at room temperature, which indicates that the forces of attraction between its particles are strong. Sugar is composed of crystal lattice structures with strong covalent bonds within each molecule and intermolecular forces holding the crystal together. Even though intermolecular forces in sugar could be hydrogen bonds and van der Waals forces similar to water, the rigid crystal structure implies that these forces are stronger in sugar than in water.
So the order of increasing forces of attraction is: oxygen < water < sugar.
What is the physical state of water at-
(a) $25^{\circ} \mathrm{C}$
(b) $0^{\circ} \mathrm{C}$
(c) $100^{\circ} \mathrm{C}$ ?
The physical state of water at different temperatures can be described as follows:
(a) At $25^{\circ} \mathrm{C}$ which is a standard room temperature, water is in the liquid state.
(b) At $0^{\circ} \mathrm{C}$, water is at the freezing point, where it can exist as ice (solid state) or as liquid, depending on the specific conditions such as pressure and the presence of impurities.
(c) At $100^{\circ} \mathrm{C}$, water is at the boiling point at standard atmospheric pressure and it exists in the gaseous state as water vapor or steam.
Give two reasons to justify-
(a) water at room temperature is a liquid.
(b) an iron almirah is a solid at room temperature.
(a) Water at room temperature is a liquid:
Intermolecular Forces: Water molecules have strong hydrogen bonds between them. At room temperature, the kinetic energy of the water molecules is not enough to overcome these forces completely, as it would be in a gas, but it's enough to allow the molecules to move past each other freely, which is characteristic of a liquid state.
Boiling and Freezing Points: The normal boiling point of water is $100^\circ C$ and the freezing point is (0^\circ C). Room temperature is generally considered to be around $20^\circ C$ to $25^\circ C$, which is within the range where the thermal energy isn't sufficient to break the intermolecular hydrogen bonds completely (which would create steam) nor is it low enough to lock the molecules into a fixed position (which would form ice). Hence, at room temperature, water remains in the liquid state.
(b) An iron almirah is a solid at room temperature:
Strong Metallic Bonds: Iron atoms are bonded by strong metallic bonds, which consist of a 'sea of electrons' that move freely around fixed, positively charged metal ions. These strong bonds give iron its solid structure at room temperature, as the kinetic energy of the atoms is not high enough to overcome these bonds and allow the atoms to flow or disperse as they would in the liquid or gas state.
Melting Point: The melting point of iron is around $1538^\circ C$, which is much higher than room temperature. Because room temperature is significantly lower than the melting point of iron, the atoms within the iron almirah have too little thermal energy to overcome the metallic bonds holding them in place, keeping the almirah in a solid state.
Why is ice at $273 \mathrm{~K}$ more effective in cooling than water at the same temperature?
Ice at $ 273 \mathrm{~K} $ $0°C$ or $32°F$ is more effective in cooling than water at the same temperature because of the energy exchange that occurs during the phase transition from solid to liquid. When ice absorbs heat, it goes through a process called melting, where it changes its state from solid to liquid. The temperature of the ice does not increase during this phase change until all of it has melted. It requires a significant amount of heat to break the hydrogen bonds holding the ice molecules in a crystalline structure. This amount of heat is known as the latent heat of fusion.
In essence, while both water and ice at $ 273 \mathrm{~K} $ have the same thermal kinetic energy (since temperature is a measure of the average kinetic energy of the particles), the ice can absorb additional energy without a temperature increase. This absorption of the heat without a rise in temperature makes ice a better cooling agent, as it draws more heat from the environment (or whatever is being cooled) in order to melt. This process is what yields its greater cooling capability compared to liquid water at the same temperature.
What produces more severe burns, boiling water or steam?
Steam can cause more severe burns than boiling water even though they are at the same temperature. This is because steam carries additional latent heat, which is the energy required for water to change phases from liquid to gas without changing temperature. When steam comes into contact with skin, it releases this additional latent heat as it condenses back into water. This means that more energy is transferred to the skin per unit of mass with steam, resulting in potentially more severe burns than boiling water at the same temperature. Thus, steam can transfer more heat to the skin upon contact, leading to more serious burns.
Name A, B, C,D,E and $F$ in the following diagram showing change in its state ( Be concise)
"Solid" is connected to "Liquid" by an arrow labeled "A," indicating the transition from solid to liquid.
"Liquid" is connected to "Gas" by an arrow labeled "B," indicating the transition from liquid to gas.
"Gas" is connected to "Liquid" by an arrow labeled "C," indicating the transition from gas to liquid.
"Liquid" is connected back to "Solid" by an arrow labeled "D," indicating the transition from liquid to solid.
There's an arrow going directly from "Solid" to "Gas," bypassing the liquid state, labeled "E." This represents sublimation.
Another arrow goes directly from "Gas" to "Solid," bypassing the liquid state, labeled "F." This represents deposition.
Above the transitions from solid to liquid to gas, there's a directive saying "Increase heat and decrease pressure," suggesting that raising temperature and lowering pressure can cause matter to transition from solid to liquid to gas.
Below the transitions from gas to liquid to solid, there's a directive saying "Decrease heat and increase pressure," suggesting that reducing temperature and increasing pressure can cause matter to transition from gas to liquid to solid.
A: Melting (Solid to Liquid) B: Boiling or Vaporization (Liquid to Gas) C: Condensation (Gas to Liquid) D: Freezing or Solidification (Liquid to Solid) E: Sublimation (Solid to Gas) F: Deposition (Gas to Solid)
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Why is air called the "breath of life"? Enumerate functions of air or atmosphere.
Air is essential for life primarily because it contains oxygen, which is crucial for the respiration of most organisms and plants. Hence, air is aptly referred to as the "breath of life."
Functions of Air or the Atmosphere:
Supports Life: Without air, neither plant nor animal life could exist.
Climate Regulation: Air, specifically the atmosphere, acts as an insulating blanket. It moderates the Earth’s temperature, making it habitable.
Temperature Control: The atmosphere helps maintain a stable temperature on Earth by preventing drastic increases during the day and slowing down heat loss during the night.
Weather Patterns: It enables the formation of weather phenomena like winds, clouds, and rain.
Protection: The atmosphere shields the Earth from harmful solar radiation and space debris.
Combustion: Air supports burning processes, which would not occur without the presence of oxygen.
In summary, air, or the atmosphere, plays a vital role in sustaining life, regulating Earth's climate, and protecting the planet from external dangers.
Due to which of the following phase change processes are water droplets seen on the outer surface of a glass containing ice-cold water?
A) Vaporization
B) Condensation
C) Sublimation
D) Fusion
The correct option is B) Condensation.
The phenomenon observed here is due to condensation. The air surrounding the glass container contains water vapor, which contributes to humidity. As this water vapor contacts the cold outer surface of the glass, it undergoes a phase change. Due to the reduced temperature of the glass's surface, the water vapor changes from its gaseous state into liquid. This transition is specifically known as condensation, resulting in water droplets forming on the outside of the glass containing ice-cold water.
Which among the following statements is true for matter?
A. It is weightless.
B. It has no mass.
C. It occupies space.
D. It has no fixed shape.
The correct answer is C. It occupies space.
Matter is defined as any substance that has mass and occupies space. Thus, all matter in the universe inherently has these properties. Consequently, the true statement about matter among the given options is that it occupies space.
Lemonade is prepared by mixing lemon juice and sugar in water. You wish to add ice to cool it. Should you add ice to the lemonade before or after dissolving sugar? In which case would it be possible to dissolve more sugar? Does water dissolve an equal amount of salt and sugar? What can be done to dissolve more salt in a saturated solution of water and salt? Name two other things that dissolve in water.
Ice Addition and Dissolving Sugar
To ensure better dissolution of sugar in lemonade, add the sugar before adding the ice. This is because sugar dissolves more readily in warm water than in cold water. Once the sugar is fully dissolved in the warm water, you can then add the ice to cool the lemonade.
Solubility of Different Substances
Water does not dissolve equal amounts of different substances. For instance, the amount of sugar water can dissolve is different from the amount of salt it can dissolve.
Increasing Solubility of Salt
If you have a saturated solution of salt and water, you can dissolve more salt by heating the solution. Heating increases the water’s capacity to hold more salt particles.
Other Water-Soluble Substances
Two other substances that dissolve in water are coffee and soap.
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