Rajasthan Board for Class 9 Science Chapter 2 Structure of Matter and Molecule are part of RBSE Solutions for Class 9 Science. Here we have given Rajasthan Board RBSE Class 9 Science Chapter 2 Structure of Matter and Molecule.
|Chapter Name||Structure of Matter and Molecule|
|Number of Questions Solved||72|
Rajasthan Board RBSE Class 9 Science Chapter 2 Structure of Matter and Molecule
Structure of Matter and Molecule Textbook Questions Solved
Objective Type Questions
When did Maharishi Kanad give the idea of Parmanu?
(A) 500 BC
(B) 100 BC
(C) 460 BC
(D) 1808 BC
What is the atomicity of oxygen in the ozone?
Which of the following substance is not a solid at room temperature?
The temperature at which matter from liquid state converts into the solid state is known as:
(A) Melting point
(B) Boiling point
(C) Freezing point
Which of the following is a mixture:
Structure of Matter and Molecule Very Short Answer Type Questions
Who first gave the knowledge of Parmanu?
Indian philosopher Maharishi Kanad
What is the approximate size of Parmanu?
The approximate size of Parmanu is 10-10 m.
Write the molecular formula of water.
A mixture of kerosene oil and water is what type of mixture?
A mixture of Kerosene oil and water is a heterogeneous mixture.
By which method would we separate the water from sandy water?
What is the atomicity of oxygen in dioxygen?
Give an example of a monoatomic molecule.
Name the state of matter in which shape and volume are definite.
Write the full form of CNG.
Compressed Natural Gas
Name the process in which liquid is converted into vapours.
Structure of Matter and Molecule Short Answer Type Questions
What is the melting point? Define it.
The melting point of a solid is the temperature at which it changes the state from solid to liquid at atmospheric pressure.
Define the latent heat of vaporisation.
Amount of heat energy required to change 1 kg of a liquid into a gas at atmospheric pressure at its boiling point is known as the latent heat of vaporisation of that liquid.
Write one difference between element and compound.
Element: An element is the basic form of matter that cannot be broken down into simpler substances by chemical reactions.
Compound: It is a substance made up of two or more elements chemically combined with one another in a fixed ratio.
What is a mixture? Explain it with an example.
In a pure substance, all the constituent particles are the same in their chemical nature. But most of the matter we see and use is constituted by more than one kind of pure substances and are known as mixtures. For e.g. milk is actually a mixture of water, fat, proteins etc. Seawater, sugar, minerals, soil, nylon, cotton, oil, paper, air etc. are all mixtures. Mixtures may be homogeneous or heterogeneous.”
Write four characteristics of the liquid state.
(1) Liquids do not have fixed shape but have fixed volume: The inter-particle forces of attraction in liquids are weaker than the interparticle forces between the particles in the solid state. However, the inter-particle forces are stronger, as compared to inter-particle forces in gases. Therefore, particles in a liquid are not fixed at their positions and can move, yet the inter-particle forces do not allow the particles to go beyond a definite limit. This keeps the volume of the liquid, constant, even when its
shape is changing. Therefore, liquids do not have fixed shape and can acquire the shape of the container, in which it is kept. However, the volume of the liquid remains the same.
(2) Liquids have lower density: As the inter-particle forces of attraction is weaker in liquids than in solid state. Thus, the number of particles per unit volume is less, which accounts for the lower density of liquids, when compared to solids.
(3) Liquids can diffuse: As the inter-particle forces in liquids are not strong enough to keep them in fixed positions, thus, the particles may flow and this accounts for the fact, that liquids can diffuse.
(4) Liquids are compressible: As the particles in a liquid can move, thus the volume of liquids can change and so, they are compressible in nature.
What is a physical change? Explain with an example.
The changes which occur without a change in composition and in chemical nature of the substance are called physical changes.
For example: The change of water in ice is a physical change because chemically, ice and liquid water both are same.
These changes are mostly reversible in nature i.e. the original substance can be further obtained by reversing the reaction conditions.
Explain the effect of pressure on gases when liquified.
The physical state of a substance can be changed by changing the pressure. An increase in pressure brings the particles closer and increases the force of attraction between them, that brings about the change.
For example: When high pressure is applied to gas and its temperature is reduced, the gas is converted to a liquid, i.e., the gas is liquified.
Thus, by applying pressure and reducing temperature gases can be liquified. Hence, we can say that pressure and temperature determine the state of a substance, whether it will be solid, liquid or gas. The pressure exerted by a gas is measured in the atmosphere. Atmospheric pressure at sea level is taken as one atmosphere which is also normal atmospheric pressure. As we go higher, atmospheric pressure decreases.
Write any three characteristics of matter.
The general characteristics of the particles of matter are as follows:
- They have space between them.
- The particles of matter are moving.
- The particles of matter are very small.
- The particles of matter attract each other.
Which type of mixture is separated by separating funnel?
Immiscible liquids in a mixture form different layers depending on their densities when allowed to stand undisturbed for some time. Each layer can be separately taken out by using a separating funnel. We can see from the figure, how kerosene oil and water can be separated by using a separating funnel.
Define compound with an example.
A compound is a pure substance, composed of two or more elements, chemically combined with one another in a fixed proportion.
For example: Water H2O, Methane CH4, etc.
The composition of a compound remains the same throughout and its constituents can only be separated by electrochemical reactions. The properties of a compound are different from its constituent elements.
Structure of Matter and Molecule Long Answer Type Questions
Explain the effect of temperature on the state of matter.
On increasing the temperature, kinetic energy of the particles increases, so they vibrate and move with greater speed. Increased energy overcomes the force of attraction between the particles and their order is disturbed. Thus, on heating, solid changes into a liquid and a liquid is changed into gas at certainly fixed temperatures. On decreasing the temperature, the change takes place in the reverse order
The temperature at which a solid melt, i.e. changes into a liquid state at the atmospheric pressure is called its melting point. The process of melting is also known as fusion. Ice melts at 0°C or 273K. The temperature at which a liquid change into a gaseous state at the atmospheric pressure is called its boiling point. Water boils at 100°C or 373 K.
The melting point of a solid or boiling point of a liquid gives an indication of the strength of the force of attraction between its particles. At melting point, a solid start melting, but its temperature does not rise till the whole of it is melted, even though heat energy is continuously supplied. This heat energy is absorbed by the solid without showing any rise in temperature and is used up in overcoming the force of attraction between the particles and making them free to move apart. It is known as latent heat (latent means are hidden).
Amount of heat energy required to change 1 kg of a solid into liquid at atmospheric pressure its melting point is known as the latent heat of fusion of that solid. Similarly, at its boiling point, a liquid starts changing into vapours, but its temperature does not rise till the whole of it changes into gas form, even though heat energy is continuously supplied. This heat energy is absorbed by the liquid without showing any rise in temperature and is used up in overcoming the force of attraction between the particles and making them free to move apart.
Amount of heat energy required to change 1 kg of a liquid into a gas at atmospheric pressure at its boiling point is known as the latent heat of vaporisation of that liquid. Changing of gas into a liquid is known as condensation. Changing of liquid into solid is known as freezing or solidification. Latent heat is given out during the process of condensation and freezing.
There are some substances which change directly from solid state to gaseous state on heating and from gaseous state to a solid state on cooling, without changing into the liquid state. Such substances are called sublime and the process is called sublimation.
Explain sublimation with an example.
Some solids have a tendency to sublime on heating, i.e. they convert directly from solid to gaseous/vapour phase on heating without passing through the liquid phase. A mixture containing such solid with any other solid can be separated by sublimation. Examples of solids that sublime are camphor, ammonium chloride, naphthalene, iodine, anthracene, etc. Hence, sublimation is used to separate such mixtures, that contain a sublimable volatile component from a non-sublimable impurity.
For example, A mixture of common salt and ammonium chloride can be separated by sublimation. The mixture is heated in a china dish, above which, inverted funnel steam of which has closed with cotton has been placed. The vapours of ammonium chloride become cool and solidify when coming in contact with the walls of the funnel and, thus solid ammonium chloride is separated. Common salt is left in the china dish.
Write the three differences between the states of solid, liquid and gas.
The differences between solids, liquids, and gases are as follows:
|(1) They have definite shape and volume||(1) They have indefinite shape but definite volume.||(1) They have an indefinite shape as well as indefinite volume.|
|(2) The inter-particle forces of attraction Eire very strong in solids.||(2) The inter-particle forces of attraction is weak in liquids.||(2) The inter-particle forces of attraction are very weak in gases.|
|(3) The inter-particle spaces are very small in solids. So, the particles are closely packed in solids.||(3) The inter-particle spaces are comparatively large in liquids so the particles in liquids are loosely packed.||(3) The inter-particle spaces are very large in gases. So, the particles in gases are very loosely packed.|
Write the two differences between the physical and chemical change?
|Physical change||Chemical change|
|(1) In this, no new substance is formed.
(2) There is no change in the molecular composition of the matter.
|(1) In this, new substances are formed.
(2) There is a change in the molecular composition of the matter.
How do we purify the substance with distillation? Explain with a diagram.
When the two liquids in the mixture are such that they boil without decomposition or chemical reaction and their boiling points have sufficient difference, more than 25°C, then they can be separated by simple distillation.
Take the given mixture of acetone and water in a distillation flask. Set the distillation apparatus as shown in the adjoining figure, using a Liebig’s condenser. When ready, start the flow of water through the condenser and slowly heat the mixture in the flask. Keeping a close watch on the thermometer readings, observe carefully, the happenings in the flask.
Structure of Matter and Molecule Additional Questions Solved
I. Multiple Choice Questions (MCQs)
Which of the following is not a matter?
(D) Cold drink
A few substances are arranged in the increasing order of forces of attraction’ between their particles. Which one of the following represents a correct arrangement?
(A) Water, Air, Wind
(B) Air, Sugar, Oil
(C) Oxygen, Water, Sugar
(D) Salt, Juice, Air
Which one of the following statement is correct?
(A) Only gases behave like fluids.
(B) Gases and solids behave like fluids.
(C) Gases and liquids behave like fluids.
(D) Only liquids are fluids.
Which of the following is not correct regarding gases?
(A) Gases exert pressure.
(B) Gases have a very weak tendency to diffuse
(C) Gases are more compressible than liquids.
(D) Gases have weak intermolecular forces of attraction.
Which of the following has the highest intermolecular forces of attraction?
(A) Liquid water
(B) Liquid ethyl alcohol
(C) Gaseous CO2
(D) Solid CO2
Which of the following correctly describes the color inside the gas jars, fifteen minutes after the glass plate is removed?
Lower gas jar Upper gas jar
(A) Dark brown Colourless
(B) Light brown Dark brown
(C) Colourless Dark brown
(D) Light brown Light brown
A substance is said to be in the liquid state if under normal pressure its:
(A) the melting point is below the room temperature
(B) the boiling point is below the room temperature
(C) the melting point is above the room temperature
(D) the boiling point is above the room temperature
Which one of the following sets of phenomena would increase on raising the temperature?
(A) Diffusion, evaporation, compression of gases
(B) Evaporation, compression of gas, solubility
(C) Evaporation, diffusion, expansion of gases
(D) Evaporation, solubility, diffusion, compression of gases
Which of the following is a heterogeneous mixture?
(A) A solution of a solid in a liquid
(B) A solution of a solid in another solid
(C) A mixture of a gas in a liquid
(D) A mixture of a solid in another solid
Which of the following is not heterogeneous?
A homogeneous system which is not a chemical compound is a mixture?
(A) Common salt
The temperature of melting ice remains constant for some time even if we continue to supply heat to the beaker. This is because of the heat energy
(A) is radiated out
(B) is used to overcome the forces of attraction between the particles
(C) is used to change the pressure on the particles
(D) is used to bring the particles of matter closer.
A saturated solution of a salt in water can be made unsaturated by:
Alum is used for making the finer clay particles in water to settle down faster. This process is known as:
A mixture consists of a soluble solid in a liquid. Which method is most suitable for obtaining both the components?
(A) Fractional distillation
Identify the chemical change in the following:
(A) Freezing of water
(B) Rusting of iron
(C) Melting of wax
(D) Glowing of a bulb
The purity of a substance cannot be checked by its:
(B) Melting point
(C) Boiling point
Which of the following mixtures can be best separated by sublimation?
(A) common salt and sodium nitrate
(B) benzene and water
(C) iodine and sand
(D) sodium sulphate and sand
Which of the following mixtures cannot be separated by using a separating funnel?
(A) Kerosene oil and water
(B) Ethyl alcohol and water
(C) Turpentine oil and water
(D) Benzene and water
Which of the following is not a chemical change?
(A) Baking of cake
(B) Ripening of fruits
(C) Formation of clouds
(D) Rancidity of butter
Structure of Matter and Molecule Board Solutions Very Short Answer Type Questions
Name the state of matter in which layers of particles can slip and slide over each other.
What is the matter?
Anything which occupies space and has mass is known as matter.
Why is ice at 273 K more effective in cooling than water at the same temperature?
Ice will take the heat of fusion from the material in contact and will cause more cooling.
What are the two ways in which the physical state of matter can be changed?
(a) By changing pressure.
(b) By changing temperature.
What is the melting point of ice?
The melting point of ice is 0°C or 273 K.
An element is a basic form of matter that cannot be broken down into simpler substances by chemical reactions.
What is meant by pure substance?
A pure substance consists of a single type of particles and all the constituent particles of that substance are the same in their chemical nature.
Where is the fractionating column fitted in a distillation apparatus?
The fractionating column is fitted in a distillation apparatus between the distillation flask and the water condenser.
Name the apparatus used for separating a mixture of immiscible liquid.
A mixture is a material containing two or more substances in varying proportions but not chemically combined.
Define the term atom.
An atom is the smallest particle of an element that can take part in a chemical reaction. It may or may not exist independently.
Atoms of most elements are not able to exist independently. ’Name two atoms which exist as independent atoms.
Noble gases such as argon (Ar), Helium (He) exist as independent atoms.
The number of atoms present in one molecule of an element or a compound is known as its atomicity.
From the following list choose elements, compounds, and mixture:
(d) Common salt
Element – Graphite (Carbon)
Compound – Sugar, Common salt.
Mixture – Air, Brass.
Structure of Matter and Molecule Solutions Short Answer Type Questions
At room temperature why oxygen is a gas while water is a liquid?
At room temperature oxygen is a gas while water is a liquid because the force of attraction present between the molecules of oxygen is weaker than the force of attraction present between the molecules of water hence, the molecules of water are strongly bonded with each other at room temperature. So, it is at ..a liquid state whereas the molecules of oxygen are not attached so strongly with each other and therefore, exist in a gaseous state.
Liquids generally have a lower density as compared to solids but you must have observed that ice floats on water. Find out why.
Liquids generally have a lower density as compared to solids. But the solid form of water, i.e., ice floats on the surface of liquid water. It indicates that the density of the solid form of water is lower than the liquid form of water. This is due to the open cage-like structure of ice. It means, in ice, some vacant spaces are left when H2O molecules get linked in ice. In water, these vacant spaces are less. Therefore, due to the larger vacant spaces, the volume of ice increases hence, density decreases. Thus, it floats over the surface of the water.
What is the importance of the melting point of a solid or boiling point of a liquid?
(a) The melting point of a solid or boiling point of a liquid gives an indication of the strength of forces of attraction between its particles.
(b) The melting point or boiling point is a test of purity of the substance, as every pure substance has a fixed shape, melting and boiling points.
Why does the temperature of a substance remain constant after it attains its melting or boiling points? Answer
The temperature of a substance remains constant during at its melting or boiling point because all the heat energy supplied to the substance is absorbed by its particles and is used up in overcoming the forces of attraction between the particles and making them free to move apart. Therefore, it does not show any rise in temperature.
Classify the following into physical changes and chemical changes:
(a) Rusting of an iron nail.
(b) Melting of butter
(c) Burning of wax candle
(d) Glowing of an electric lamp.
(a) Chemical change
(b) Physical change
(c) Chemical change
(d) Physical change
How is melting point related to intermolecular forces of attraction? Why is latent heat of vaporisation higher than latent heat of fusion?
Greater the intermolecular forces of attraction, higher will be the melting point. The energy required to convert solid into liquid is less than the energy required to convert liquid into vapours due to the small difference in the forces of attraction between solid and liquid than in liquid and gas.
How will you determine the boiling point of water, experimentally? Draw a neat and labeled diagram.
1. Take a boiling tube having a cork with one hole.
2. Insert a thermometer into it.
3. Keep thermometer above water.
4. Start heating the boiling tube.
5. Note the temperature at which liquid water changes into vapours completely and temperature of thermometer becomes constant. It is the boiling point of water. Observe the temperature when the boiling of water takes place.
Conclusion Water boils at 100°C or 373 K and the temperature remains constant till water changes into vapours completely.
Name A, B, C, D, E and F in the following diagram showing a change in its state: Increase heat and decrease pressure
(A) Melting (fusion)
(D) Freezing (Solidification)
(F) Solidification of vapours (sublimation).
Identify the separation technique used:
(1) To separate the components of the ink.
(2) To separate cream from milk.
(3) To separate alcohol from water.
(4) To separate mustard oil from water.
(4) Separating funnel.
Why is crystallisation considered a better technique than evaporation?
Crystallisation is considered a better technique than evaporation because:
- The impurities which remain dissolved in the solution even after evaporation, are removed during crystallisation.
- Some solids decompose while some, like sugar, get charred when all the liquid evaporates which does not happen during crystallisation.
State the condition for using the method of centrifugation to separate contents of a mixture. State the principle involved in this process.
The density of substances to be separated should be different. The denser particles are forced to settle at the bottom and the lighter particles stay at the top when rotated at high speed in centrifugal machine.
Classify the following as elements and compounds.
Elements: Silver, Mercury. Compounds: Methane, water.
Name the separation technique you would apply for the separation of the following?
- Sodium chloride from its solution in water.
- Tea leaves from tea.
- Iron pins from sand.
- Different pigments from an extract of leaves.
- Butter from curd.
- Fine mud particles suspended in water.
- Evaporation or crystallization
- Magnetic separation
What determines the state of a substance? Suggest a method to liquefy gases. Water droplets are observed on the outer surface of a glass tumbler containing ice cold water. Give reason.
Pressure and temperature determine the state of a substance. It is because water vapors get condensed on the cold surface of the glass. Gases can be liquified at high pressure and low temperature.
Structure of Matter and Molecule Long Answer Type Questions
What are the different states of matter? Name the factors which determine the state of matter. Explain.
Matter exists in three states:
Solid, Liquid and Gas.
The state of a matter is determined by two factors:
1. Temperature and
These two factors respectively control
(1) the kinetic energy of the particles and
(2) the distance between the particles thereby, the intermolecular force of attraction. If intermolecular forces are the very large and kinetic energy of the particles is much less, the matter will be in the solid state.
If intermolecular forces are very weak and kinetic energy of the particles is very large that can overcome the force of intermolecular attraction and set them free to roam about, the matter will be in the gaseous state.
Explain the following:
- Ice floats over water.
- Dry ice sublimes.
- Two cubes of ice are pressed hard between the palm when the pressure is released the two cubes join together.
- The temperature of the water does not change once the boiling starts, in spite of the heat being supplied.
- Ice has an open cage, like structure due to which its volume increases and density decrease. Therefore it floats over water.
- The vapour pressure of dry ice becomes equal to the atmospheric pressure much before its melting point and hence it sublimes.
- When pressure is applied to ice cubes, the freezing point decreases. As a result, some of the ice in between the two cubes melts. The energy needed for melting is taken from the surroundings. Hence, when pressure is released, then the two cubes join together.
- The heat supplied at the boiling point of a liquid is used up in overcoming the forces of attraction between the particles of a liquid, during the change of liquid state to gaseous state without increasing their kinetic energy. Thus, the temperature remains constant.
What is meant by fractional distillation? How is it differ from simple distillation? What part of the fractional distillation apparatus makes it more efficient and possess an advantage over simple distillation process? Explain using a diagram.
Give one example of fractional distillation in industry.
The process in which a volatile liquid is first vaporised at its boiling point and the vapours are condensed to get back the liquid in pure form is called distillation.
If the difference in boiling points of the liquids in the mixture is less than 25°C, the method of fractional distillation is used to separate them. Fractional distillation method is same as simple distillation except that in the apparatus a fractionating column is fitted in between the distillation flask and the condenser.
It makes the apparatus more efficient. A fractionating column is a wide tube packed with glass beads, which provides a larger surface area for cooling. Vapours of liquid having higher boiling point get condensed on the surface of these beads, while the vapours of lower boiling point liquid pass on upwards. Length of the column also increases the efficiency of the process.
Example: In an oil refinery, the different fractions of petroleum products are separated by fractional distillation of crude petroleum.
A child worked to separate the mixture of dyes constituting a sample of ink. He marked a line by the ink on the filter paper and placed the filter paper in a glass containing water as shown in the figure. The filter paper was removed when the water moved near the top of the filter paper.
(a) What would you expect to see, if the ink contains three different coloured components?
(b) Name the technique used by the child.
(c) Suggest one more application of this technique.
(a) If the ink contains three different coloured components, we see spots of different colours at different heights on the filter paper as seen in the figure. The most soluble in water appears in the highest position, the less soluble in water appears in the middle position and the least soluble in water appears at the lowest position on the chromatograph.
(c) This technique is also used to separate and identify amino acids obtained by hydrolysis of blood.
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