Class 9 Science Chapter 1 Notes Matter In Our Surroundings
NCERT Class 9 Science Chapter 1 Notes Matter In Our Surroundings on this step-by-step answer guide . In some of State Boards and CBSE schools, students are taught thru NCERT books. As the chapter comes to an end, students are requested few questions in an exercising to evaluate their knowledge of the chapter. Students regularly want guidance dealing with those NCERT Notes. It’s most effective natural to get stuck withinside the exercises while solving them so that you could assist students rating better marks, we have provided grade by grade NCERT answers for all exercises of Class 9 Science Matter in our Surroundings so you can be searching for assist from them. Students have to solve those exercises carefully as questions withinside the very last exams are requested from those so these exercises at once have an impact on students’ final score. Find all NCERT Notes for Class nine Science Matter in Our Surroundings below and prepare for your tests easily.
Chapter 1 : Matter In Our Surroundings
Anything that has mass and occupies space (i.e., has volume) is called matter.
Everything in the universe is made up of matter.
Everything in this universe is made up of material which scientists have named “matter”. The air breath, the food we eat.
Characteristics of Particles of matter
- Particles of matter are continuously moving
- Particle of matter are continuously maving, that is, they possess kinetic energy. As the temperature rises, particles moves faster because kinetic energy of the particles increases .
Particles of matter have space between them
- When we make tea, coffee or lemonade (nimbu pani), particles of one type of matter get into the space between particles of the other.
- This shows that there is enough space between particles of matter.
Particles of matter attract each other
- When we open a water tap, try to break the stream of water with your fingers, can we do this? No, because the stream of water remains together.
- Particles of water are held together because of the force of attraction between them.
- Intermixing of particles of two different types of matter on their own is called diffusion. on heating diffusion becomes fastrer.
STATES OF MATTER
Matter around us is found to exist in three different physical states, i.e., solid, liquid and gas.
These different states of matter arise due to variation in the characteristics of the particles of matter.
THE SOLID STATE
Some common examples of solids are iron , copper , gold , sugar , common salt , wood , rock , ice , etc etc.
- The solid state of matter , the constituent particles ( atoms , molecules or ions ) are very closely spaced, i.e., the interparticle distance is very small.
- The intermolecular forces between the constituent particles of a solid are very strong and therefore, the particles in a solid are held in fixed positions and have very little freedom of movement.
- The particles can simply vibrate about their mean positions.
Characteristic Properties of Solids
The solid state of matter is characterized by the following properties:
- Solids have definite shape and volume: This is because of the presence of very strong cohesive forces between the constituent particles of a solid.
- Solids are rigid and incompressible: As the constituent particles in a solid are very closely packed with practically no space between the particles, the solids have slight or no compressibility.
- Solids in general have high density: The solid state of a matter has Density is defined as mass per higher density as compared to its liquid state and much higher than its gaseous state.
- SolidsSolids do not flow: As the constituent particles in a solid are held closely in fixed positions due to very strong forces of cohesion , they are unable to flow. Therefore , solids , normally , do not show the phenomenon of diffusion.
- Solids are characterized by high melting and boiling points: Due to strong forces of cohesion between the constituent particles of a solid, more heat energy is required to these forces, therefore, solids, in general, have high melting and boiling points.
THE LIQUID STATE
Some common examples of liquids are water , milk , oil , fruit juice , petrol , etc.
- The liquid state of matter, the constituent particles are packed loosely, i.e.,interparticle space is more than in solid.
- The cohesive forces, though weaker than in solid, are strong enough to keep the constituent particles fairly close to each other.
- The constituent particles have restricted freedom of movement.
Characteristic Properties of Liquids
- Liquids have definite volume but do not have definite shape: A given quantity of a liquid has a fixed volume at a given temperature because the cohesive forces are strong enough to keep the constituent particles together. They do not have definite shape.
- Liquids have slight compressibility: liquids are slightly more compressible than solids because in case of liquids, there is greater interparticle space.
- Liquids have lower density than their corresponding solid state: In case of liquids, the particles of matter are packed loosely. Therefore, liquids are less dense.
- Liquids diffuse more readily than solids: The particles of liquids move faster and diffuse more readily than in solids. As a result, diffusion in liquids is faster than in solids.
- The boiling points of liquids are normally much lower than the solids: It is because the cohesive forces operating between the constituent particles in liquids are weaker as compared to that in solids.
THE GASEOUS STATE
Some familiar examples of gases are oxygen, nitrogen, hydrogen, carbon dioxide (air actually a mixture of gases), etc. Like ai, most of the gases are invisible.
In case of gases, the constituent particles are far away from each other and therefore, practically, no force of cohesion exists between the particles.
The constituent particles have high degree of freedom and they move randomly in all directions with high speeds.
Characteristic Properties of Gases
1. Gases do not have definite shape and volume: Due to lack ( or absence ) of interparticle forces and presence of high velocity of molecules.
2. Gases have high compressibility: In case of gases , the particles are far apart and therefore , they can be pushed closer by applying pressure . Due to high compressibility , a large volume of a gas can be compressed into a container.
3. Gases have very low densities: The density of the gaseous state of a matter is much low as compared to its liquid and solid states. This is because interparticle spaces in gases are very large.
4. Gases have high rate of diffusion. Gases have high rate of diffusion because the particles in the gases are moving freely in all possible directions with high speeds.
5. Gases flow freely . Because of the absence of cohesive force between the particles in gaseous state, the molecules of gases move independently at high speeds.
Change of state of matter
- Change of matter from one physical state to another is called change of state
How can matter change its state
- Changing temperature
- Changing pressure
- Changing temperature and pressure both
Effect of change of temperature
- The temperature at which a solid melts to form liquid at atmospheric pressure is called its melting point.
- Melting point of ice is 273.16 K ( 0 ° C ).
- During melting the temperature ofice does not rise even though heat is being supplied continuously due to latent heat of fusion.
- This latent heat of fusion is used up to overcome the forces of attraction between ice particles.
- At 0 ° C energy of water particles is much more than the energy of particles of ice at 0° C .
Latent Heat of Fusion: The amount of heat required to change 1 kg solid to its liquid state (at its melting point) at atmospheric pressure.
( ii ) Boiling Point:
- The temperature at which a liquid boils to form vapors at atmospheric pressure is called its boiling point.
- Boiling point of water is 373 K ( 100 ° C +273 = 373 K ).
Latent Heat of Vapourization:
- The amount of heat required to change I kg liquid to its gaseous state ( at its boiling point ) at atmospheric pressure.
- During boiling the temperature of water does not rise even though heat is being supplied continuously as this heat of vaporization is used up to over the forces of attraction between water particles.
- At 100 ° C , the energy of water vapors is much more than the energy of water at 100 ° C. So , we can change one state of matter to another state by changing temperature.
At 25° C, water is liquid.
At 0° C, water is solid (ice).
At 100° C, water is gaseous state (steam).
(iii) Sublimation: The change of solid directly into vapors on heating and of vapors into solid on cooling without passing through the intervening liquid state is called sublimation.
Example: When camphor or ammonium chloride is heated in a China dish covered by an inverted funnel (with cotton plug in its upper open end), the vapors of ammonium chloride are converted into solid ammonium chloride on coming in contact with the cold inner walls of the funnel.
Effect of Change of Pressure:
- If we compress a gas in a cylinder, the distance between the particles of gas is reduced and finally gas is liquefied on lowering temperature.
- By applying high pressure, the particles of a gas can be brought close together.
- Solid carbon dioxide (dry ice) is changed into carbon dioxide gas directly without changing into liquid when pressure is reduced to one atmospheric pressure.
- Thus, states of matter i.e., solid, liquid, gas are determined by temperature & pressure.
- A surface phenomenon in which liquid changes into vapors at any temperature below its boiling point is called evaporation.
- Particles on the surface of a liquid have higher kinetic energy than others, so they break.
- The forces of attraction between the particles & escape from the surface of liquid in the form of vapors.
Factors affecting evaporation: Rate of evaporation depends on:
(a) Exposed surface area: On increasing surface area of liquid , rate of evaporation increases.
(b) Increase in temperature: Increases kinetic energy of particles hence rate of evaporation increases.
(c) Humidity: When the humidity of air (degree of dampness of air) is low, evaporation rate is increased. More humidity, less evaporation
(d) Wind : When wind speed increases, rate of evaporation also increases.
Evaporation always causes cooling:
The cooling caused by evaporation is based on the fact that when a liquid evaporates, it takes latent heat of vaporization from surroundings which on losing heat get cooled.
- When we put acetone on our hand , it gets evapourized by taking heat from our hand and our hand feels cool.
- We should wear cotton clothes in summer to keep cool and comfortable as cotton is good absorber of water, so it absorbs the sweat from our body and exposes it to air for evaporation of sweat Thus cools our body.
- Often people sprinkle water on ground during summer. This water takes heat from ground and surrounding air to evaporate, thus making the place cool.
Benefits of NCERT Class 9 Science Chapter 1 Notes Matter In Our Surroundings
NCERT Class 9 Science Chapter 1 Notes Matter In Our Surroundings contains extremely important points, and for each chapter, each concept has been simplified to make it easier to remember and increase your chances of achieving excellent exam results. Exam Preparation References Here are some tips on how these solutions can help you prepare for the exam.
- This helps students solve many of the problems in each chapter and encourages them to make their concepts more meaningful.
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