Chemistry important short questions for class 9 are here. Chapter 1 (States of matter and phase changes), most important short questions. Prepare the best for the exam.
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Constructed Response Questions (Chapter 1: States of Matter and Phase Changes)
Q1: How does a supercritical state look like?
Answer: A supercritical state occurs when a substance is heated and pressurized past its critical point. In this state, the boundary between liquid and gas disappears. It looks like a homogeneous, cloudy fluid that has the density of a liquid but expands to fill its container like a gas.
Q2: In what way is plasma created in a fluorescent tube?
Answer: When the switch is turned on, electricity passes through the gas (usually helium or neon) inside the tube. This electrical energy strips electrons from the gas atoms, converting the gas into a mixture of free electrons and positive ions (which is plasma). This plasma glows and produces light.
Q3: Most of the molecules we study in biochemistry are organic in nature. Where does the difference exist in organic and biochemistry branches of Chemistry?
Answer:
- Organic Chemistry: This branch deals only with the structure, properties, and reactions of carbon-containing compounds (except oxides, carbonates, etc.), regardless of whether they are living or non-living.
- Biochemistry: This branch deals specifically with the chemical substances and chemical reactions that take place inside living organisms (like humans, plants, and animals), such as the metabolism of carbohydrates and proteins.
Q4: Give the reason for the brilliance shown by diamond. Can you improve it?
Answer: The brilliance of a diamond is due to total internal reflection. Light enters the diamond and gets trapped, bouncing off the internal faces because of its high refractive index and specific cut. Its brilliance can be improved by cutting and polishing its faces at highly precise angles to maximize light reflection.
Q5: Explain the dissolution of sodium chloride (NaCl) in water?
Answer: Water is a polar solvent with partial positive (Hδ+) and partial negative (Oδ-) charges. When NaCl is added to water, the positive ends of water molecules attract the negative chloride ions (Cl–), and the negative ends of water molecules attract the positive sodium ions (Na+). This pulling force breaks the ionic lattice, causing NaCl to dissolve.
Q6: Why do different compounds have different solubilities in water at a particular temperature?
Answer: Solubility depends on the rule “like dissolves like” and the strength of solute-solvent forces. Different compounds have different chemical structures, polarities, and lattice energies. Therefore, polar compounds dissolve easily in polar water, while non-polar or highly tightly bound ionic lattices do not.
Q7: Why can NaCl not be crystallized from water just like KNO3?
Answer: The solubility of Potassium Nitrate (KNO3) increases significantly when temperature increases, meaning it crystallizes easily when a hot solution is cooled. However, the solubility of NaCl remains almost constant with temperature change. Thus, simple cooling does not crystallize NaCl; the water must be evaporated to obtain crystals.
Q8: Why is graphite slippery to touch? Which property of graphite enables it to be used as a lubricant?
Answer:
- Reason: Graphite has a layered hexagonal structure. The layers are held together by weak Van der Waals forces, allowing them to easily slide over each other, making it slippery to touch.
- Property: This ability of its layers to slide smoothly over one another allows graphite to be used as a dry lubricant.
All Short Question + Additional
The video description is here to understand the full concept for all short questions.
Q.1: Why is there a need to divide chemistry into many branches?
To understand the widely spread complex subject of chemistry and to concentrate on its specific aspects, chemistry is divided into many distinct branches. The purpose of this division is.
1. It helps in understanding the fundamental principles of chemical reactions and bonding.
2. It allows scientists to develop new materials and technologies, improving everything.
3. These branches have distinct areas of study for the scientist to focus on and to achieve breakthroughs and advancements.
Q.2: Reactions may take place due to electrons present outside the nucleus, or they may take place inside the nucleus. Which branches of chemistry cover these two types of reactions?
Reactions that involve electrons outside the nucleus are studied in physical chemistry, and the reactions that take place inside the nucleus are part of nuclear chemistry.
Q.3: What type of problems are solved in analytical chemistry?
In analytical chemistry, problems related to the identification, composition, and quantification of substances are solved. This branch of chemistry deals with the analysis of different substances by the use of instruments to analyze the matter.
Q.4: Both graphite and graphene have a hexagonal layered structure. What is the difference?
Graphite.
- It is a three-dimensional layered structure of a hexagonal ring of carbon.
- Example. The pencil is made up of a mixture of graphite and clay.
Graphene
- It is a two-dimensional single layer of carbon atoms arranged in a hexagonal pattern.
- Example. It is used for the development of a flexible, lightweight touchscreen.
Q.5: Why are supercritical fluids important?
Ans. Supercritical fluids are important because they exhibit properties of both liquids and gases when they are at a specific temperature and pressure. These fluids are used in various processes such as extraction, chromatography, and chemical reactions due to their unique properties, like high diffusion, low viscosity, and high solvating power.
Q.6: In which state does matter exist in the Sun?
Ans. In the sun, matter primarily exists in the plasma state. Plasma is not a generally seen form of matter. It is composed of particles with very high kinetic energy. It exists in fluorescent tubes, lightning, and welding arcs. Plasma can be considered as a partially ionized gas containing electrons, ·ions, photons, etc.
Q.7: What is the importance of graphene?
Graphene is important because it is a single layer of carbon atoms arranged in a hexagonal pattern. Graphene has many applications in electronics, energy storage devices and sensor and even in medical devices. Because graphene has. Exceptional properties such as tough, flexible, and light material with high resistance.
Q.8: Which form of matter do most of the material things in this world belong to?
Most of the material things in the world belong to the state of matter known as solids. Solids have a fixed shape and volume, and their particles are closely packed together in an ordered form.
Q.9: Which elements are found in a pure state on Earth?
Ans. Gold (Au), Silver (Ag), Copper (Cu), Platinum (Pt), Sulphur (S) are found in pure state on earth.
Q. 10: How variation of solubility at different temperatures be useful for us?
- The increase in solubility of solids in liquids with an increase in temperature may be used to purify a crystal of potassium nitrate. Pure solids commonly appear as beautifully shaped crystals.
- Generally, the solubility of gases decreases with the increase in temperature. Carbon dioxide gas is also more soluble in water at low temperatures. Soda water bottles are thus stored in the refrigerator to keep carbon dioxide gas dissolved in the water for a longer period.
Q. 11: What is chemistry?
Chemistry is the science that deals with the properties, composition, and structure of matter. It also studied the physical and chemical changes in the matter and the laws or principles that govern these changes.
Q. 12: What is Physical Chemistry
This branch investigates how substances behave at the atomic and molecular levels. It provides a clear explanation as to how fundamental physical laws governing our world caused atoms in the molecules to show specific characteristics, and it turns react to give huge structures related to life.
Scope: Physical chemistry is also used to predict and change the rates of reaction, thus optimizing the conditions to carry out the reaction on an industrial scale.
Q. 13: Water is the difference between organic and inorganic chemistry.
Organic Chemistry
It is the branch of chemistry that deals with the carbon compounds (hydrocarbons and their derivatives) other than their simple salts like carbonates, oxides, and carbides.
Inorganic chemistry
It is the study of the synthesis, composition, properties, and structure of the elements and compounds that contain little or no carbon.
Q. 14: Difference between Environmental & Analytical chemistry.
Environmental chemistry: It is the scientific study of the chemical and biochemical phenomena that occur on this planet. In this subject, we study the sources, reactions, effects, and fates of chemical species in the air, soil, and water environments. Scope: Without this, it would be impossible to study the effects humans have on the environment through the release of chemicals.
Analytical chemistry: This branch of chemistry deals with the analysis of different substances. It involves the separation, identification, and determination of the concentration of the material things.
Q. 15: Difference between Biochemistry & Nuclear chemistry.
Ans. Biochemistry: It is the branch of chemistry in which we understand life through chemical processes. It is the study of chemical substances and vital processes occurring in living organisms.
Nuclear chemistry: Nuclear chemistry deals with the reactions taking place in the nucleus of an atom. It deals with radioactivity, nuclear processes, and transformations in the nuclei of atoms.
Q. 16: What is the difference between polymer and geochemistry?
Polymer Chemistry: Polymers are large molecules made by linking together a series of building blocks. (Polymer chemistry focuses on the properties, structure, and synthesis of polymers and macromolecules. Many materials present in the living organisms · including proteins, cellulose, and nucleic acids,s are naturally occurring polymers.
Geochemistry: The study of the chemical composition of Earth and its sources and minerals is called geochemistry. Apart from its use in minerals exploration, geochemical mapping today has applications in environmental monitoring, forestry, and medical research.
Q.17 A lunar mission has recently brought samples from the Moon. Point to the branch of chemistry these experiments are related to:
- Determining its composition: Analytical chemistry.
- Studying the physical properties of materials, it contains: Physical chemistry.
- Carrying out chemical reactions with usual inorganic reagents: Inorganic chemistry.
Q.18 Define a saturated solution and give an example.
A solution containing the maximum amount of solute at a given temperature. Example: A solution of 5.3 molar sodium chloride at room temperature.
Q.19 Difference between medicinal & Astrochemistry.
Medicinal Chemistry involves designing and synthesizing medicines or drugs beneficial for mankind. Astrochemistry is the study of molecules and ions in space and the interstellar universe.
Q.20 What is meant by Nuclear Process?
It refers to any process occurring within the nucleus of an atom, such as radioactive decay, nuclear fission, and nuclear fusion.
Q.21 For what purpose geothermal heat pump used?
It uses a pump to transfer underground water into buildings to heat them in winter and cool them in summer.
States of Matter
Q.22 Define matter. Give examples.
Anything that has mass and occupies space is called matter; examples include air, water, rocks, and people.
Q.23 Why do gases not have a definite shape and volume?
Because gas molecules are widely apart with no order and have weak intermolecular forces.
Q.24 Why solid have a definite shape & volume?
Because their molecules are closely attached and have significant intermolecular forces.
Q.25 Why do gases show the property of compressibility?
Because molecules are widely apart with no order and weak intermolecular forces, allowing them to be easily compressed.
Q.26 Describe the gaseous state of matter.
Matter in this state has no definite shape and volume, occupies all available space, and has very weak intermolecular forces.
Q.27 What is meant by solid?
Matter that has a definite shape and volume is called a solid, such as wood, coal, or plastic.
Q.28 What are the physical states of matter?
There are four states: i) Gas, ii) Liquid, iii) Solid, and iv) Plasma.
Q.29 How can matter change its state?
Energy can change matter states; for example, solids become liquids or gases when heated.
Q.30 What is plasma? Write its uses.
Plasma is composed of particles with very high kinetic energy. It exists in fluorescent tubes, lightning, and welding arcs.
Q.31 What is a liquid crystal?
A state of matter with properties between conventional liquids and crystalline solids. They are used in display devices like computer monitors, clocks, and watches.
Q.32 What are the classifications of matter?
Matter is classified as Substances (Elements and Compounds) and Mixtures (Homogeneous and Heterogeneous). Element, Compound, and Mixture
Q.33 How are rocks formed?
Rocks are composed of different types of minerals such as granite, mica, and limestone.
Q.34 Which was the first element created in the laboratory?
Technetium is the first element created in the laboratory.
Q.35 Write the method to remove the impurities in a mixture?
Ans. Impurities can be removed by filtration, evaporation, and crystallization.
Q.36 Why compound show a chemical formula?
Because they have a fixed ratio by mass and are formed by the chemical combination of elements.
Q.37 Define element.
The simplest form of matter is made up of the same type of atoms with the same atomic number, which cannot be broken down simpler by ordinary chemical means.
Q.38 Define compound.
When two or more elements chemically combine through a chemical reaction to form a new substance.
Q.39 Define mixture. Give example.
Mixtures are the physical combination of substances without a fixed ratio by mass. Examples include air and steel.
Q.40 Define the term allotropy with examples.
Elements exist in more than one structural form with different physical and chemical properties. Example: Oxygen exists as O₂ and O₃ (ozone).
Q.41 What is the difference between diamond and graphite?
Diamond has a giant macromolecular rigid tetrahedral structure and is a non-conductor of electricity. Graphite has layered hexagonal rings and is a good conductor of electricity.
Q.42 What do you know about Buckminster fullerene (C₆₀)? / Why is fullerene stable at high temperatures and pressures?
It consists of spheres of atoms in pentagons and hexagons. They are stable at high temperatures/pressures due to their covalent nature and unique cage-like structure.
Q.43 How are bucky balls made?
They have a football-like hollow ring structure made of twenty hexagons and twelve pentagons.
Solutions and Solubility
Q.44 Define solution. Give a few characteristics of the true solution.
A homogenized mixture of solute particles in a solvent. Characteristics: particles cannot be seen by the naked eye and pass through filter paper without leaving precipitate.
Q.45 Define suspension. Give a few characteristics of suspension.
A mixture where solute particles do not dissolve. Characteristics: particles can be seen, settle down over time, and cannot pass through filter paper.
Q.46 Define colloidal solution. Give a few characteristics of a colloidal solution.
A solution where solute particles do not homogenize with the solvent. Characteristics: particles are larger than true solutions but too small for the naked eye, do not settle, and pass through filter paper.
Q.47 How can the formation of mixtures be useful in daily life?
Mixtures are essential as they constitute the air we breathe, the food we consume, and the fluids in our bodies.
Q.48 How is an unsaturated solution formed?
It is a solution that can dissolve more solute at a particular temperature.
Q.49 Justify with an example that the solubility of a salt increases with an increase in temperature.
When salt like KNO₃ dissolves, heat is absorbed to break attractive forces; therefore, solubility increases with temperature.
Q.50 Define solubility.
The number of grams of solute dissolved in 100g of solvent at a particular temperature.
Q.51 Why does the solubility of Li₂CO₃ and CaCrO₄ decrease with the increase in temperature?
They dissolve with the evolution of heat, because the energy is released, solubility decreases as temperature increases.
