Unit 1: States of Matter and Phase Changes — Short Questions

To understand the widely spread complex subject of chemistry and to concentrate on its specific aspects, chemistry is divided into many distinct branches. The purposes of this division is
• It helps in understanding the fundamental principles of chemical reactions and bonding.
• It allows scientists to develop new materials and technologies, improving everything products.
• These branches have distinct areas of study for the scientists to focus on and to achieve breakthroughs and advancements.

Reactions that involve electrons outside the nucleus are studied in physical chemistry and reactions that take place inside the nucleus are part of nuclear 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 use of instruments to analyze the matter.

Graphite i. It is a three-dimensional layered structure of hexagonal rings of carbon.
ii. Example: The pencil is made up of a mixture of graphite and clay.

Graphene i. It is a two dimensional single layer of carbon atoms arranged in a hexagonal pattern.
ii. Example: It is used in development of flexible, light weight touch screens

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.

In the sun, matter primarily exists in the plasma state. Plasma is not so 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.

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 sensors and even in medical devices. Because, graphene has exceptional properties such as tough, flexible and light material with a high resistance.

Most of the material things in this 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.

Experiment | Branch of Chemistry
1. Determining its composition. | Ans. Analytical chemistry
2. Studying the physical properties of materials it contains. | Ans. Physical chemistry
3. Carrying out chemicals reactions with usual inorganic reagents. | Ans. Inorganic chemistry

Gold (Au), Silver (Ag), Copper (Cu), Platinum (Pt), Sulphur (S) are found in pure state on Earth.

Astatine(At),Radium(Ra),Iodine (I),Uranium (U) and Beryllium (Be) are present in very small amounts of Earth.

i) The increase in the solubility of solids in liquids with increase in temperature may be used to purify crystal of potassium nitrate. Pure solids commonly appear as beautifully shaped crystals.
ii) Generally the solubility of gases decreases with increase in temperature. Carbon dioxide gas is also more soluble in water at low temperature. Soda water bottles are thus stored in the refrigerator to keep carbon dioxide gas dissolved in water for a longer period of time.

Chemistry is the science which deals with the properties composition and the structure of matter. It also studies the physical and chemical changes in matter and the laws or principles which govern these changes.

This branch investigates how substances behave at atomic or molecular levels. It provides clear explanation as to how fundamental physical laws governing our world cause atoms and molecules to show specific characteristics and it .turn react to give huge structures related to life.

Scope Physical chemistry is also used to predict and change the rates of reaction and thus optimize the conditions to carry out the reaction on industrial scale.

Organic chemistry It is the branch of chemistry that deals with the carbon compounds (hydrocarbons and their derivatives) other than its simple salts like carbonates, oxides and carbides.

Inorganic chemistry It is the study of the synthesis, composition, properties and structure of elements and compounds that contain little or no carbon.

Environment chemistry It is the scientific study of the chemical and biochemical phenomena that occur in this planet. In this subject, we study the sources, reactions, effects and fates of chemical species in the air, soil and water environments. 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 separation, identification and determination of the concentration of the material things.

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 transformation in the nuclei of atoms

Polymer Chemistry Polymers are large molecules made by linking together a series of building blocks. (Polymer chemistry focuses on the structure and synthesis of polymers and macromolecules. Many materials present in the living organisms including proteins, cellulose and nucleic acids are naturally occurring polymers.

Geochemistry The study of 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.

Medicinal Chemistry In this branch of chemistry, the chemist tries to design and synthesize a medicine or a drug which is beneficial for mankind.

Astrochemistry It is the study of molecules and ions recurring in space and interstellar space. In this discipline we study the abundance and reactions of molecules and ions in the universe and interaction of these species with radiation.

Nuclear process refer to any process that occurs within the nucleus of an atom. Such as Radioactive decay, Nuclear fission, Nuclear fusion.

Geothermal heat pump uses a pump to transfer underground water into the buildings during the winter to heat them and in the summer to cool them.

Anything that has mass and occupies space is called matter. This makes air, water, rocks and even people examples of matter.

Gases do not have a definite shape & volume because gas molecules are widely apart with no order and have weak intermolecular forces.

Solid have definite shape/volume because their molecules are closely attached and have significant intermolecular forces.

Because molecule widely apart with no order and weak intermolecular forces. This makes gases easily compressibility.

Matter in gaseous state does not have definite shape and volume. Therefore, gases occupy all the available space. Gases have very weak intermolecular forces.

Matter that has a definite shape and volume is called solid. For example, wood, coal, plastic etc.

There are four states of matter.
i) Gas ii) Liquid
iii) Solid iv) Plasma

Energy can change matter into different states. For example, solids become liquids or gases when heated. At very high temperatures or when subjected to a strong electric field, the gas transforms into plasma. Under normal condition, most substances remain in one distinct state: solid, liquid or gas. Temperatures and energy levels on the earth are not sufficient to ionize atoms and create plasma.

Plasma is not so 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.

Liquid crystal is state of matter whose properties are between those of conventional liquids and those of crystalline solids. Liquid crystals are used in display devices including computer monitors, clocks, watches and navigation systems.

Matter can be classified as:
i. Substance (Pure matter)
ii. Mixture (Impure matter)
1. Substance can be classified as:
a) Element b) Compound
2. Mixtures can be classified as:
a) Homogeneous mixture
b) Heterogeneous mixture

Rocks are composed of different types of minerals such as granite, mica and limestone.

Technetium was first element created by scientists in the laboratory.

We can removed the impurities in a mixture by Filtration, Evaporation and crystallization.

Compound show chemical formula because they have a fixed ratio by mass and they are formed by chemical combination of elements.

The simplest form of matter made up the same type of atoms, having same atomic numbers and cannot be broken down into simpler substance by ordinary chemical means.

When two or more elements chemically combine, meaning undergo a .chemical reaction to form a new substance, this is called a compound.

Mixtures are the physical combination of substances. A mixture that does not contain the same types of particles. It is a substance formed when two or more substances physically combine without any fixed ratio by mass.

Elements may exist in more than one structural forms which can exhibit quite different physical and chemical properties. These forms are called allotropic forms and phenomenon is called allotropy.

For example -
Allotropic forms of oxygen:
Oxygen exists in two allotropic forms namely oxygen (O₂) and ozone (O₃).

Diamond | Graphite
i. Diamond has a giant macromolecular structure. | i. Graphite has a layered structure of hexagonal rings of carbon.
ii. Carbon is covalently bonded to four other carbon atoms forming rigid network tetrahedral in shape. | ii. Graphite is composed of flat two dimensional layers of hexagonally arranged carbon atoms.
iii. Diamond is non-conductor of electricity. | iii. Graphite is a good conductor of electricity.

Buckminster fullerene (C₆₀) consists of spheres made of atoms arranged in pentagons and hexagons. Fullerenes are stable at high temperatures and high pressures. Being covalent in nature, they are soluble in organic solvents. The fullerene structure is unique in that the molecule is not charged, has no boundaries and has no unpaired electrons. They have a cage like structure. Fullerene C₆₀ has a low melting point. It is soft and cannot conduct electricity.

Buckyballs, also known as fullerenes, have a football like fused hollow ring structure made up of twenty hexagons and twelve pentagons. Each of its 60 carbon atoms are bonded to 3 carbon atoms.

A solution is such a mixture in which solute particles are completely homogenized in the solvent e.g. dissolution of sodium chloride or copper sulphate in water.

Characteristics The solute particles in such solution cannot be seen by the naked eye. If a solution is filtered, these particles pass through the pores of filter paper leaving no precipitate. Such a solution is called a true solution.

A suspension is a mixture in which solute particles do not dissolve in the solvent.

Characteristics -
We can actually see these particles.
If a suspension is kept for some time, these particles settle down. Again, if this suspension is filtered, the particles in it cannot pass through the pores of filter paper like the particles of a true solution.

In colloidal solution the solute particles do not homogenize with solvent.

Characteristics -
These particles are a little bit bigger than the solute particles present in the true solution but not big enough to be seen with a naked eye like the particles present in a suspension. If kept for some time, the particles of a colloidal solution do not settle down. On filtration, these particles pass through the filter paper like particles of true solution. Starch solution and white of an egg are the common examples of colloidal solutions.

Mixtures are closely related to our everyday lives. The air we breathe, the foods we consume, the fluids in our body, the solids like steel we use, are all either homogeneous or heterogeneous mixture.

A solution containing maximum amount of solute at a given temperature is called a saturated solution.

For example If the solutions of table sugar and sodium chloride are prepared, it is found that 36 g of sodium chloride can dissolve in 100 g of water at 20°C to give a saturated solution. Against this 203.9 g of table sugar can dissolve in water at 20°C to give its saturated solution.

A solution which can dissolve more amount of a solute at a particular temperature is called an unsaturated solution.

For example Take about 100g of water in a beaker add to it 5g of table sugar and stir it. The sugar will dissolve in water. Then add another 5g of sugar and stir. This will also dissolve it.

When a salt like KNO₃, is dissolved in water, heat is absorbed. It means heat is required to break the attractive forces between ions of solute. Therefore, solubility of such salt increases with increase of temperature.

Solubility is defined as the number of grams of the solute dissolved in 100g of solvent at a particular temperature.

Li₂CO₃ and CaCrO₄ dissolve in water with the evolution of heat, therefore solubility of such salts decrease with the increase of temperature. In such cases attractive forces among the solute particles are weaker and solute-solvent interaction are stronger. As a result, there is release of energy.

In a supercritical state, a substance looks like a dense fluid that show properties of both gases and a liquid. It doesn't have a distinct boundary between liquid and gas. So, it can fill a container like a gas while still being dense like a liquid. Supercritical fluids are often clear and can flow easily.

In a fluorescent tube, plasma is created by applying a high voltage current at low pressure to the tube which ionizes the gas inside. This ionization process causes the gas to convert into a plasma state, emitting light as the excited electrons return to their ground state. This is how the fluorescent tube produces light

Biochemistry | Organic Chemistry
i. 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. | i. Organic chemistry: It is the branch of chemistry that deals with the carbon compounds (hydrocarbons and their derivatives) other than its simple salts like carbonates, oxides and carbides.
ii. Biochemistry provides insights into the structure and function of molecules such as proteins, carbohydrates, lipids and nucleic acids. | ii. Organic compounds are found in all forms of life and are also essential for life.

To enhance the brilliance of diamond, they can be cut and polished in specific ways to optimize the reflection and refraction of light within the stone. The cut of a diamond such as the proportions and angles greatly influences how light interacts with the diamond affecting its brilliance and sparkle.

The dissolution of NaCl occurs when the ions of the NaCl separate in water due to the polar nature of water molecules. The partially charged ends of water molecules attract and surround the positive and negative ions of NaCl. Due to this, the attraction between sodium ions and chloride ions break apart and thus NaCl dissolve in water

Different solutes have different solubilities in a water. For example, If the solutions of table sugar and sodium chloride are prepared, it is found that 36 g of sodium chloride can dissolve in 100 g of water at 20°C to give a saturated solution. Against this 203.9 g of table sugar can dissolve in water at 20°C to give its saturated solution. In other words, the solubility of table sugar in water is far greater than that of sodium chloride at 20°C. This is due to the fact that sugar molecules are larger than salt ions, so more water molecules can surround a single sugar molecule, causing it to dissolve in larger amounts.

The solubility of potassium nitrate increase significantly with the increase in temperature and on cooling excess potassium nitrate crystallizes out from water. On the other hand, in case of sodium chloride, the solubility does not increase with increase in temperature so the NaCl does not crystallizes out on cooling. That's why, NaCl cannot by crystallized from water like KNO₃.

Graphite is slippery to touch because of its layered structure. The layers in graphite are held together by weak forces allowing them to slide over each other easily. This property of graphite enables it to be used as a lubricant.