This section contains Matter in our surroundings class 9 notes pdf, Chapter 1 Science Class 9 notes. These notes are very useful for the students of class 9th from both NCERT as well as CBSE. These notes for class 9 science have been prepared by the science experts who have been teaching science at various levels for past many years.
Matter in our surroundings class 9 Questions Answers, Chapter 1 Science Class 9 notes
This section contains Matter in our surroundings class 9 Questions Answers, Chapter 1 Science Class 9 notes. These NCERT solutions have been prepared by well experienced science teachers. Go through these notes to boost your exam preparation.
Which of the flowing are matter? Chair, air, love, smell, heat, almonds, thoughts, cold, cold drink, smell of perfume?
Chair, air, almonds and cold drink.
Give reason for your observation: The smell of hot sizzling food reaches you several meters away, but to get the smell from cold food you have to go close?
The rate of diffusion increases with the rise of temperature therefore the smell of hot sizzling food reaches us several meters away. The particles of the aroma of hot food mix with the particles of air spread and reaches us several meters away. But when the food is cold we have to go close to get the smell as the rate of diffusion is less.
A diver is able to cut through water in a swimming pool. Which property of matter does this observation shows?
The water offers minimum resistance to the device divers body so he will not get hurt.
What are the characteristics of the Particles of the matter?
The important characteristics of the particles of the matter are as follows:
(1)The particle of matter are very very small: This is indicated by the experiment when we dissolve 2-3 crystals of potassium permagnate in a 100ml of water & then dilute it many times (6-7) by taking 10 ml of potassium permagnate ( KMnO4 ) and 90 ml of water at each step progressively the eight pink colour thus indicating these 2-3 crystals of potassium permagnate contains millions of particles.
(2) The particle of matter have space between them: This is indicated when we dissolve 50 gms of sugar in 100 ml of water. The resultant solution is only 100 ml thus shows there were space between water molecules in which sugar particles get accumulated.
(3)The particle of matter are constantly moving: This is indicated when we light an agerbati in one corner of room the fragrance spreads in the whole room quickly by diffusion of smelling particles.
(4) The particle of matter attracts each other: There are some forces of attraction between the particles of same substances which bind them together these are called cohesive forces. The force of cohesion is different in the particles of different kinds of matter, the force of attraction is maximum in the particles of solid matter and minimum in particles of gas.
The mass per unit volume of a substance is called density(D=m/v). Arrange the following in order of increasing density, air, exhaust from chimneys, honey water, chalk, cotton & iron.
Iron > chalk > cotton > honey > water > air > exhaust from chimneys.
Tabulate the differences in the characteristics of states of matter.
| Solids | Liquids | Gases |
| solids have fixed shape and fixed volume | Liquids have fixed volume but no fixed shape | Gases have neither fixed shape nor fixed volume |
| Space between the molecules is minimum | Space between the molecules is a little more | Space between the molecules is maximum |
| The intermolecular forces are strongest | The intermolecular forces are medium in nature | The intermolecular forces are least |
| The kinetic energy of molecules is minimum | The kinetic energy of molecules is medium | The kinetic energy of molecules is maximum |
Comment upon the following:
Rigidity:- A substance which is flexible or does not bend is called rigid substance. Rigidity is shown by solids.
Compressibility:- A substance whose volume can be decreased by increasing pressure is called compressibility. Compressibility is shown by gases and liquids shown slightly compressibility and solids does not show compressibility.
Fluidity:- A substance which has not fixed shape and can flow are called fluids. It includes liquids and gases.
Filling a gas container:- Gases can fill the container completely whether the amount of gas is small or large.
Shape:- Solids have a fixed shape. Liquids and gases have not any fixed shape.
Kinetic energy:- The energy associated with moving particles is called kinetic energy. The particles of solids has minimum kinetic energy, the particles gases has highest kinetic energy while the particles of liquids has intermediate kinetic energy.
Density:- Density is defined as the ratio of mass and volume. It is highest in solids, followed by liquids and gases.
Give reasons for the following:
(1) A gas fills completely the vessel in which it is kept.
Ans:- Because due to high kinetic energy and negligible force of attraction. The molecules of gas are moving with high speed in all directions.
(2) A gas exerts pressure on the walls of the container.
The kinetic energy of the particles in the gaseous state is maximum and the particles move about randomly at high speed and hit each other and also the walls of the container. Thus exerts force on the walls of the container.
(3) A wooden table should be called a solid.
A wooden table should be called a solid because it is rigid and can not be compressed easily. It has definite shape and volume.
(4) We can easily move our hands in air but to do the same through a solid block of wood we need a karate expert.
It is because the inter-molecular forces in wood are the strongest (solid) and negligible in air (gas).
(5) Liquids generally have lower density as compared to solids, but you must have observed that ice floats on water. Find out why.
Ice floats in water because the density of ice (0.92g/cm3 ) is less than water (1.0g/cm3).
Convert the following temperature to Celsius scale:
(1) 300K
We know that: Kelvin scale = temperature on Celsius scale + 273.
Therefore, 300= temp on Celsius scale +273
=> Temperature on Celsius scale = 300-273= 27°
(2) 573 K
We know that:
Temperature on Kelvin scale = temperature on Celsius scale+ 273.
573= temperature on Celsius scale +273
=> Temp of Celsius scale = 573-273=300°C.
What is the physical state of water at:
(1) 250°C
Ans: Gaseous State
(2) 100°C
Ans: Gaseous state
For any substance, why does the temperature remain constant during the change of state?
It is because the heat gets used up in changing the state by helping the particles over come the force of attraction between them.
Suggest a method to liquefy atmospheric gases.
Applying pressure and reducing temperature we can liquefy atmospheric gases.
Why does a desert cooler cool better on a hot dry day?
Because the higher temperature on a hot day increases the rate of evaporation of water and the dryness of air (low humidity of air) also increased the rate of evaporation of water. And due to increased rate of evaporation of water a desert room cooler cools better on a hot and dry day.
How does the water kept in an earthen pot (matka) become cool during summer?
During summer water is kept in earthen wares to keep it cool because earthen wares (matka) has got a number fine pores all around. Water comes out through the pores and changed into vapors by taking heat from the inner water with the result the water inside the matka gets cooled.
Why does our palm feel cold when we put some acetone or petrol or perfume on it?
This is due to the fact that to change from the liquid to vapour state, Sprit /acetone /petrol /ether requires latent heat of vaporization which it takes from hand (palm) since the hand loses heat and thus gets cooled.
Why are we able to sip hot tea or milk/coffee faster from a saucer rather than a cup?
Saucer has more surface area than a cup therefore rate of evaporation is more in case of saucer than in the cup. Hence more cooling will be in the case of saucer. It is due to this reason that we are able to sip hot tea or milk faster from a saucer than from a cup.
What type of clothes should we wear in summer?
We should wear cotton clothes in hot summer days to keep ourselves cool and comfortable. When we get sweated in summer days, the cotton being the good absorber, absorbs the sweat from our body and exposes it to the air for evaporation. The evaporation of this sweat cools our body.
Convert the following temperatures to the Kelvin scale.
(1) 25°C
Temperature on Celsius scale=temperature on Kelvin scale + 273
=> temp on celsius scale = 25°C+273 = 298K
(2) 373°C
Temperature on Celsius scale = temperature on Kelvin scale + 273
=> temp on celsius scale = 273°C+373= 646K.
Give reasons for the following observations.
(1)why Naphthalene balls disappear with time without leaving any solid.
Naphthalene balls disappear without leaving any solid because they sublime. They change directly from solid to gas without changing into liquids.
(2) Why We can get the smell of perfume sitting several meters away.
Because the smelling substance of the perfume (in gaseous state) diffuses more rapidly thus we are able to smell a perfume sitting several meters away.
Arrange the following substances in increasing order of forces of attraction between the particles-water, sugar, oxygen.
sugar > Water > oxygen.
What is the physical state of water at:
(1) 25° C.
Ans:- Liquid.
(2) 0oC.
Ans:- Solid.
(3) 100°C.
Ans:- Gas.
Give two reasons to justify why Water at room temperature is a liquid?
water at room temperature is a liquid because:
- Its boiling point is higher than the room temperature and its freezing point is below the room temperature.
- Water at room temperature flows and has no fixed shape.
Give to reasons to justify why an iron almirah is a solid at room temperature.
- It is because both melting point and boiling point of iron are greater than the room temperature.
- The iron almirah at room temperature has a fixed shape and fixed volume.
Why is ice at 273K more effective in cooling than water at the same temperature?
This is due to the fact that for melting, the ice takes the latent heat from the substance to get converted into liquid water and hence cools a substance more effectively than water at same temperature.
What produces more severe burns, boiling water or steam?
Steam produces more severe burns as compared to water at 100°c because steam has more energy than water at 373k (100°c) this is because particles in steam have absorbed extra energy in the form of latent heat of vaporization.
Name A,B,C,D,E and F in the following diagram showing change in its state;
- A= Fusion
- B= Evaporation
- C= Condensation
- D= solidification (freezing)
- E&F= Sublimation
What is diffusion?
The process by which different substances mix as a result of the random motion of their molecules is called diffusion or the movement of molecules of a substances from the region of higher concentration to the region of lower concentration is called diffusion.
Define Brownian movement (motion).
The zigzag movement of the small particles suspended in a liquid ( or Gas ) is called Brownian motion.
Define melting point?
The temperature at which solid melts to became a liquid is called melting point.
Define boiling point?
The temperature at which a liquid change into gas/ vapors is called boiling point.
Define Sublimation?
The change of solid directly into the vapour on heating of the vapour into solid on coaling is known as sublimation.
Define evaporation / vapourisation?
The phenomenon of change of a liquid into gas at any temperature below its boiling point is known as evaporation.
Define latent heat?
The latent heat of a substance is the amount of heat absorbed or given out by unit mass of the substance upon changing its state without change of temperature. It is of two types:
- Latent heat of fusion:- The amount of heat energy required to change 1 kg of solid into liquid at atmospheric pressure at its melting point is known as latent heat of fusion.
- Latent heat of vapourisation:- The amount of heat energy required to change 1 kg of liquid into vapour state (gas) at atmospheric pressure at its melting point is known as latent heat of vapourisation.
Define fusion?
The process of melting or changed of solid state into liquid state is known as fusion.
Define solidification?
The process of changing of a liquid into solid state is known as solidification. It is some times also called freezing, because in solidification we generally decrease the temperature.
Define condensation?
The process of changing of vapour into liquid state is known as condensation.
What is plasma?
Plasma is mixture of free electrons and ions . It is considered fourth state of matter. Plasma occurs naturally in stars including sun.
Explain the diffusion of KMNO4 solution in water?
Potassium permagnate is a purple coloured solid substance which when dissolved in water forms purple coloured solution. When this purple coloured solution is added to pure water in a beaker, the purple colour spreads through out the beaker. This spread of purple colour in the whole container is due to diffusion of potassium permagnate molecules in the water.
Explain the diffusion of copper sulphate in water?
Copper sulphate crystals are blue in colour. When a few crystals of copper sulphate are placed at the bottom of beaker containing water then the water slowly turns blue. This is due to the diffusion of blue coloured copper sulphate molecule into the water, where molecules of copper sulphate move in water from higher concentration to lower concentration.
Explain the properties of solids, liquids & gases.
The solid have following characteristic properties:
- Solid have fixed shape & fixed volume.
- Solid can not be compressed much.
- Solid have high density.
- Solid do not fill the container completely.
- Solid do not flow.
The liquid have following characteristic properties:
- Liquids have fixed volume but not fixed shape.
- Liquids can be compressed slightly.
- Liquids have density less than that of solid.
- They do not fill the container completely.
- Liquid can flow.
The solid have following characteristic properties:
- Gases have neither fixed shape & nor fixed
- volume.
- Gases can be compressed easily.
- Gases have very low density.
- Gases fill the container completely.
- Gases flow easily.
How will you separate a mixture containing Kerosene and petrol ( Difference in their boiling points is more than 25c) which are miscible with each other?
- 1-Take the mixture in a distillation flask fit it with a thermometer.
- Arrange the apparatus as shown in figure.
- Heat the mixture slowly keeping a close watch at thermometer.
- The petrol vaporizes, condenses in the condenser & can be collected from the conducer or outlet.
- Kerosene is left in the distillation flask.
What type of material are separated by the technique of crystallization?
Those mixture are separated by the technique of crystallization whose components have different solubilities in water (Solvent).
Write the step you would use for making tea. Use the words solution, solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.
Take about 20ml of tap water (solvent) in a beaker. Heat it on burner till it boils. Add some tea leaves which are insoluble in water. Filter it hot and collect the filtrate in a cup. Used tea leaves (residue) are left behind on the seive. Now add a little sugar (solute) and milk (solute) to it. Stir it to dissolve. Now tea is ready to drink which is a solution.
Also Check: The fundamental unit of life Class 09 Notes pdf
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