Best NCERT Solutions for Class 9 Science Chapter 1-Matters in Our Surroundings Learning Directly Learning Directly

Best NCERT Solutions for Class 9 Science Chapter 1-Matters in Our Surroundings

Best NCERT Solutions for Class 9 Science Chapter 1-Matters in Our Surroundings .“Matter in Our Surroundings” is a fundamental concept in science that introduces students to the basic principles of matter and its various forms. It’s often one of the first topics in physics and chemistry courses.

Question 1. Which of the following is the matter?

Chair, air, love, smell, hate, almonds, thought, cold, cold drink, smell of perfume.

Answer: Anything that has mass and takes up space is considered matter. Solid, liquid, and gaseous forms of matter are the three types. We can identify which of these three states is a matter based on:

-Given their set shapes, the chair and almond are considered to be in a solid state of matter.

-A cold drink has a tendency to flow, therefore it is in a liquid form.

-Since both air and scent have free-moving gaseous particles, they will likewise be categorised as gaseous states of matter.

-Although love, hate, cold, scent, and thought are merely human emotions or perceptions, they are not regarded as matter since they lack mass or physical space.

Question 2. Give reasons for the following observation:

The smell of hot sizzling food reaches you several meters away, but to get the smell of cold food you have to go close.

Answer: The scent of our mother’s freshly made, sizzling food wafts into our room from the kitchen, but after a while we no longer detect the smell of it. This phenomenon can be explained by the fact that the rate of diffusion increases with temperature because a high temperature increases the kinetic energy of food particles to diffuse in the air. Compared to cold food particles, hot food particles have a higher temperature, which allows their molecules to diffuse more easily in the atmosphere. Best NCERT Solutions for Class 9 Science Chapter 1-Matters in Our Surroundings

Question 3: A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?

Answer: This can be explained by the way matter has the ability to draw particles to itself, which also determines the particles’ stiffness and shape. When compared to liquid and gas, the force of attraction is greatest in the case of a solid, indicating that the particles of the solid are closely bonded to one another. Liquid particles, on the other hand, have fewer forces of attraction, indicating that there is space between them and making cutting them easier. For this reason, we can argue that a diver can cut through water in a swimming pool because there are fewer forces of attraction between the molecules of water.

Question 4: What are the characteristics of particles of matter?

Answer:

Anything that has mass and takes up space is considered matter. Solid, liquid, and gaseous forms of matter are the three types.

The following is a description of matter’s primary properties:

-Matter particles have space between them, with gas having the largest order of spacing while liquid and solid have the least amount of space between their particles.

-In all three states of matter, matter particles are always in motion.

-Strong forces cause matter particles to be drawn to one another, which facilitates their binding. Attraction between particles is highly high in solids, low in liquids, and fairly low in gases.

Exercise -2

Question 1: The mass per unit volume of a substance is called density (density = mass/volume). Arrange the following in order of increasing density − air, exhaust from the chimney, honey, water, chalk, cotton, and iron.

Answer:

Since density depends on both mass and volume, a substance’s density will increase with mass. Since heavier particles have a higher mass than lighter ones, the following can be used to represent the order in which a substance’s density increases:

Air \ Chimney exhaust \ Cotton \ Water ~ Honey \ Chalk \ Iron.

Question 2:A. Tabulate the differences in the characteristics of states of matter.

Answer: Anything that has mass and takes up space is considered matter. Solid, liquid, and gaseous forms of matter are the three types.

called Solid, Liquid, and Gas.

Property	Solid State	Liquid State	Gaseous State
Shape and volume	It has a fixed shape and volume.	It has no definite shape unless it takes the shape of the vessel in which they are kept. It has a fixed volume.	It does not contain any shape or not have any fixed volume.
Compressibility	It is incompressible in nature.	It is compressible but to a smaller extent.	It is highly compressible in nature.
Forces of attraction	The force of attraction is highest in case of solids.	The force of attraction between liquid particles is less than solid particles but greater than gas.	The force of attraction in this case is very low.
Randomness	Particles of solid have no tendency to move freely therefore, these are not termed to be random.	Liquid particles have a tendency to move freely therefore these are random in nature.	Gaseous particles are very free to move so these are also random in nature.

B.Comment upon the following: rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy, and density.

Answer: 1. Rigidity: It is described as matter’s propensity to oppose a change in shape.

2. Compressibility: the capacity of matter to lose volume in response to any kind of external stimulus.

3. Fluidity: Particles’ propensity to flow This characteristic is evident in gases and liquids, which are also referred to as fluids.

4. Filling a Gas Container: Gases lack both a defined volume and clear shape. When gases are full, they conform to the shape of the container. Therefore, filling a gas container refers to the gas taking on the shape of the container.

5. Shape: Shape and fixed volume and border correspond. A solid’s shape is unchangeable.

6. Kinetic Energy: particles that generate energy because they are always moving.

Question 3: Give Reasons:

A. A Gas Fills Completely the Vessel in Which it is Kept.

Answer: Because there is very little force of attraction between the particles in the gas, the particles have a tendency to travel freely in all directions. Similar to water, petrol can adopt the shape of the container it is stored in. As a result, we can state that the gas entirely fills the vessel.

B. A Gas Exerts Pressure on the Walls of the Container.

Answer: Because there are fewer forces of attraction between the gas particles, they can travel freely. As a result, these gaseous particles constantly and more forcefully smash with the container walls and one another. The force that gas particles produce per unit area is referred to as pressure. This indicates that the gas is applying pressure to the container walls.

C. A wooden table should be called a solid.

Answer: A wooden table is very rigid by nature, meaning that it has a defined shape that is difficult to alter and a defined volume. Strong intermolecular forces keep the shape stable, allowing it to acquire all the characteristics of a solid and be classified as one.

D. We can easily move our hands in the air, but to do the same through a solid block of wood, we need a karate expert.

Answer: There is a lot of space between air particles since there are very few forces of attraction between them. However, because of its strong attraction to other particles, wood has very little space between them and is consequently regarded as stiff. This explains why we can move our hands through the air with ease, but not through a solid block of wood. We need a karate specialist for this.

Question 4: Liquids generally have a lower density than solids. But you must have observed that ice floats on water. Find out why.

Answer: Density, as we all know, is defined as mass per unit volume. As a result, as a substance’s volume increases, its density decreases because their relationships are inversely proportionate.

Since ice is solid by nature, its molecules are closely bonded by strong intermolecular forces and have a smaller volume. In contrast, liquids have a larger volume and a tendency to move freely because of weak intermolecular forces.

This indicates that water has a greater volume and a lower density, which causes it to float atop water.

Exercise – 3

Question 1: Convert the following temperature to Celsius scale:

A. 300 K

Answer: The two primary temperature measurement scales are Celsius and Kelvin. We may obtain the value in degrees Celsius by deducting the 273K from the provided value. The formula that relates to degrees Celsius looks like this:

X \circ C = (X - 273)

300 K = (300 - 273) \circ C = 27 \circ C

B. 573 K

Answer: $573 K = (573 - 273)^{\circ} C = 300^{\circ} C$

Question 2: What is the physical state of water at:

A. $25 0^{o} C$

Answer: The physical state of matter, whether it is a solid, liquid, or gas, correlates to its condition.

250 degrees Celsius. As is common knowledge, water exists in a gaseous state at 100°C, when it begins to boil. Thus, this establishes that water is a gas at 250°C.

B. $100^{o} C$

Answer: $100^{o} C$ – Water exists in both liquid and gaseous phases at this temperature since it is the point at which it begins to boil.

Question 3: For any substance, why does the temperature remain constant during the change of state?

Answer: This can be explained by the fact that the substance’s intermolecular forces of attraction are broken by the heat we apply to raise its temperature. This heat will also match latent heat, or heat that is absorbed or released during a state transition. Because all of the energy is spent, the temperature doesn’t change.

Question 4: Suggest a method to liquefy atmospheric gases.

Answer: The gases that are present in the atmosphere are referred to as atmospheric gases. By lowering their temperature and adding the appropriate pressure, it can be liquefied or turned into a liquid.

Best NCERT Solutions for Class 9 Science Chapter 1-Matters in Our Surroundings

Exercise – 4

Question 1: Why does a desert cooler cool better on a hot dry day?

Answer: This can be explained by the process of evaporation, which is the process by which the liquid particles absorb energy from their surroundings and cause cooling. The rate of evaporation is generally dependent upon the amount of water vapour present in the air; if the amount of water vapour present in the air is greater then the rate of evaporation is greater, or vice versa. On a hot, dry day, the amount of water vapour present in the air is relatively low, so this will evaporate easily and make its

Question 2: How does water kept in an earthen pot (matka) become cool during summer?

Answer: An earthen pot, also known as a matka, is often composed of sand particles with numerous microscopic pores, which allow the water within to drain and cool the surrounding area. For this reason, during the summer, people stored their water in earthen pots.

Question 3: Why does our palm feel cold when we put some acetone or petrol or perfume on it?

Answer: Perfume, acetone, and petrol are examples of organic molecules that are volatile by nature; volatile substances are those that evaporate quickly and evaporate. It is well known that as these organic liquids evaporate, their particles absorb energy from their surroundings or the palm’s surface, causing the area to become slightly cooler. This explains why applying acetone, fuel, or perfume to our palms makes it feel chilly.

4: Why are we able to sip hot tea or milk faster from a saucer than a cup?

Answer: This can also be explained in terms of evaporation rate as we are aware that evaporation has a cooling effect and that it is based on surface area, with higher evaporation occurring on bigger surfaces. Since the area of the saucer is more than that of the cup, evaporation will be higher when the surface area is larger. We can therefore conclude that liquid cools more quickly in a saucer than it does in a cup, which enables us to drink hot milk or tea from a saucer more quickly than from a cup.

Question 5: What type of clothes should we wear in the summer?

Answer: Wearing cotton or light-colored clothing is necessary during the summer months because these materials can absorb more perspiration from the body, transmit the liquid sweat to the atmosphere, and hasten the evaporation process. Our bodies feel cooler in cotton clothing due to the evaporation process than in synthetic or woollen clothing.

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NCERT EXERCISE

Question 1: Convert the following temperature to Celsius scale:

A. 300 K

X \circ C = (X - 273)

300 K = (300 - 273) \circ C = 27 \circ C

B. 573 K

Answer: $573 K = (573 - 273)^{\circ} C = 300^{\circ} C$

Question 2: Convert the following temperature to Kelvin scale:

A. $25^{\circ} C$

Answer: The two primary temperature measurement scales are Celsius and Kelvin. We may get the value in degrees Celsius by adding 273K to the supplied value. The formula that relates to degrees Celsius looks like this:

0 \circ C = 273 K

27 o C = (27 + 273) K = 300 K

B. $373^{\circ} C$

Answer: $373^{o} C = (373 + 273) K = 646 K$

Question 3: Give reason for the following observations.

A. Naphthalene balls disappear with time without leaving any solid.

Answer: Sublimation, which states that a solid is changed straight from solid to gaseous state without first being liquid, provides an explanation for this phenomena. One of the chemicals that sublimates readily at ambient temperature is naphthalene. For this reason, we can state that naphthalene balls eventually vanish without leaving any trace.

B. We can get the smell of perfume sitting several meters away.

Answer: Because there are extremely few internuclear interactions in gaseous particles, their molecules can move around freely and have a high kinetic energy. We are able to detect perfume from a distance of several meters because scent molecules combine with atmospheric particles and drift into the atmosphere.

Question 4: Arrange the following substances in increasing order of forces of attraction between particles − water, sugar, oxygen.

Answer: The force that draws molecules together is known as the forces of attraction, and in the case of a solid, these forces are much stronger than in a liquid or gas.

In this instance, sugar is described as solid and having stronger attraction forces.

Comparatively speaking, water is a liquid with more forces of attraction than gases, but less than gases.

One gas that has very little force attraction in it is oxygen.

As a result, the increasing order of attraction between the oxygen, sugar, and water particles is

Oxygen < Water < Sugar

Question 5: What is the physical state of water at:

A. $25^{o} C$

Answer: The physical state of matter, whether it is a solid, liquid, or gas, correlates to its condition.25°C

As is well knowledge, water persists in a liquid state above 0°C and melts at lower temperatures.

This means that water is defined as existing in a liquid condition at 25°C.

B. $0^{o} C$

Answer: $0^{\circ} C$ –It is the temperature at which water begins to melt, turning from ice into liquid. At this temperature, water can exist in both a liquid and a solid state.

C. $100^{o} C$

Answer: $100^{\circ} C$ – Water exists in both liquid and gaseous phases at this temperature since it is the point at which it begins to boil.

Question 6: Give two reasons to justify:

A. water at room temperature is a liquid.

Answer: We discover that water is liquid at room temperature, which makes sense for the reasons listed below:

-Water has a defined volume but no set shape; it can take on the shape of the container in which it is kept.

-It leans towards flowing.

-possess weak forces acting between the molecules in their particles.

We may state that water is liquid at room temperature because all of these represent the characteristics of liquids.

B. At room temperature, an iron almirah is a solid.

-The iron almirah in our room is considered sturdy for the reasons listed below:

-It has a defined volume and a set shape.

-Strong intermolecular forces exist between its constituent particles.

-stiff by nature and challenging to compress.

Since they all explain a solid’s characteristic, we may state that the almirah is solid at room temperature.

Question 7: Why is ice at 273 K more effective in cooling than water at the same temperature?

Answer: The ice and water in this case are both at the same temperature, or 273 K. At 273 K, however, ice has less energy than water. This can be explained by the fact that water has latent heat of fusion, which is an extra energy that ice does not have. Consequently, we can conclude that at 273 K, ice cools more quickly than water.

Question 8: What produces more severe burns, boiling water or steam?

Answer: It is believed that the temperature of both steam and water is 373 K. However, steam has a higher energy content than boiling water. This can be explained by the fact that water has additional energy in the form of latent heat of fusion. Steam, therefore, burns more severely than boiling water. Best NCERT Solutions for Class 9 Science Chapter 1-Matters in Our Surroundings