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States of matter

• Matter exists in nature in different forms, the three basic states of matter are Solid, Liquid and Gas.
• Apart from these three, there are two more states of matter that exist which we do not see in our everyday life.
• They are Plasma & Bose-Einstein condensate.

Key Points

​Properties of Solid - 

• In solids, the particles are closely packed and the gaps between the particles are tiny and hence it is tough to compress them.
• Solid has a fixed shape and volume.
• Example: Dust, books etc.

Properties of Liquid -

• In a liquid, particles are less tightly packed as compared to solids and less difficult to compress as compare to solid because particles have less space between them to move but more than the solid.
• Liquids take the shape of the container in which they are kept.
• Liquids have definite volume but no fixed shape.
• Example: water, juice etc.

Properties of Gas -

• In gases, particles are far apart from each other, the force of attraction between the particles is negligible and they can move freely.
• The gaseous state has the highest compressibility as compared to solids and liquids.
• Gases have neither a fixed volume nor a fixed shape.
• Example: Air, water vapour, gases.

Important Points

• Feeling of cold: It is a feeling, feelings cannot be categorized under any state of matter.

Confusion Points

Humidity:

• Humidity is the concentration of water vapour present in the air.
• Water vapour, the gaseous state of water, is generally invisible to the human eye.
• Humidity indicates the likelihood for precipitation, dew, or fog to be present.
• It is a gaseous state of matter.

​Thus, the feeling of cold is not a matter.

Key PointsCelsius scale:

• The Celsius scale is nowadays set in such a way that Zero degrees C is the temperature at which water freezes.
• At the other end of the scale, 100 degrees Celsius is the boiling point of water.
• In this scale, a lower fixed point (ice point) is designated as 0° and the upper fixed point (steam point) is designated as 100°.
• The temperature measured on this scale was all in degrees Celsius (°C).

Kelvin scale:

• On the Kelvin scale, the boiling point of the water is considered to be 373.15 K and its freezing point is 273.15 K.
• Whereas it was assumed that at 0 K there is no relative motion of particles.
• The change in temperature of 1° K corresponds to a change of less than 1°C on the Celsius scale.

Important Points

How to convert Celsius to Kelvin:

• 0 degrees Celsius is equal to 273.15 degrees Kelvin
• The temperature T in Kelvin (K) is equal to the temperature T in degrees Celsius (°C) plus 273.15
• 0 °C = 273.15 K
• T(K) = T(°C) + 273.15
• So, T (K) = T (10°C) + 273.15 = 283.15 K ~ 283 K

​Thus, 10°C temperature is equal to 283 K.

 Additional Information

Fahrenheit scale

• The change in temperature of 1°F corresponds to a change of less than 1°C on the Celsius scale.
• On the Fahrenheit scale, water freezes at 32 degrees and boils at 212 degrees.
• The boiling and freezing point are therefore 180 degrees apart.
• Normal body temperature is considered to be 98.6 °F (in real life it fluctuates around this value).
• Absolute zero is defined as -459.67°F.​

Conversion Formulas

• Celsius
• °C = (°F - 32) × 5/9
• °C = K - 273.15
• Fahrenheit
• °F = (°C × 9/5) + 32
• °F = ((K - 273.15) x 9/5) + 32
• Kelvin
• K = °C + 273.15
• K = ((°F - 32) × 5/9) + 273.15

• Elements that lose electrons in a chemical reaction are called metals.
• Elements that accept electrons in a chemical reaction are called non-metals.

Key Points Difference between Metals and Non-metals:

Important PointsLead:  

• Lead is a chemical element with the symbol Pb and atomic number 82.
• It is a heavy metal that is denser than most common materials.
• Lead is soft and malleable, and also has a relatively low melting point.
• When freshly cut, lead is silvery with a hint of blue; it tarnishes to a dull grey colour when exposed to air.

Bismuth:

• Bismuth is a high-density, silvery, pink-tinged brittle metal.
• Bismuth is brittle and so it is usually mixed with other metals to make it useful.
• Its alloys with tin or cadmium have low melting points and are used in fire detectors and extinguishers, electric fuses and solders.

Mistake Points 

• Although bismuth is a metal it is selected as a non-metal because of all the given options, it is the element that shows the least metal-like properties.

Thus, Bismuth is not a metal.

Key Points

Compounds:

• A compound is a substance made up of two or more elements chemically combined in a fixed proportion by mass.
• A compound cannot be separated into its constituents by physical processes.
• It can only be separated into its constituents by chemical processes.
• The properties of a compound are entirely different from those of its constituents.
• Energy (in the form of heat, light, etc.) is usually given out or absorbed during the preparation of a compound.
• The composition of a compound is fixed, the constituents are present in a fixed proportion by mass.
• A compound has a definite formula.
• A compound has a fixed melting point, boiling point.
• Example: washing soda (Na₂CO₃), quicklime (CaO).

Important PointsBrass: 

• Brass is a mixture of the elements of copper and zinc.

Confusion PointsMarble:

• Marble is typically more than 95%-99% calcium carbonate.
• Calcium carbonate (CaCO₃) is a compound.

​Thus, Brass is not a compound.

Additional InformationMixture:

• The mixture contains two or more substances mixed, but neither chemically as well as not in exact quantity.
• A mixture shows the properties of its constituents but the properties of a compound are entirely different from its constituents
• Mixtures do not have a certain formula.
• A mixture may be homogeneous or heterogeneous.
• The constituents of a mixture can be separated by physical methods.

​The correct answer is Liquid and Vapour

• Water is the only substance on Earth that naturally occurs in three physical states: solid, liquid, and gas.
• Water is an inorganic, transparent, tasteless, odourless, and nearly colourless chemical substance.
• It is the main constituent of Earth's hydrosphere and the fluids of all known living organisms.
• Water is called the universal solvent because it is capable of dissolving more substances than any other liquid.

Key Points

States of water:

• Depending on the temperature and atmospheric pressure, water can change from one state to another, a process called physical phase change.
• The physical state of water at 25°C is liquid.
• The physical state of water can be both liquid and solid at 0°C.
• It is so because 0°C is the melting point of ice as well as the freezing point of water.
• The physical state of water can be both liquid or gas at 1000C.
• It is so because 1000C is the boiling point of water as well as the condensation temperature of steam.

Thus, the state of water at 100°C is liquid and vapour.

The correct answer Dalton.

Key Points

Indivisibility of matter:

• It is also known as the Atomic theory
• It is a scientific theory of the nature of matter, which states that matter is composed of discrete units called atoms.
• The atomic theory of matter was first proposed by John Dalton.
• Dalton's atomic theory was the first complete attempt to describe all the matter in the terms of atoms and their properties.
• Many of the scientists gave the concept for the atomic theory of matter.
• But, the first atomic theory of matter was proposed by John Dalton.
• John Dalton (1766-1844) developed the first useful atomic theory of matter.

Important PointsDalton's atomic theory

• All matter is made up of tiny, indivisible particles called atoms.
• All atoms of a specific element are identical in mass, size, and other properties. However, atoms of different elements exhibit different properties and vary in mass and size.
• Atoms can neither be created nor destroyed. Furthermore, atoms cannot be divided into smaller particles.
• Atoms of different elements can combine in fixed whole-number ratios to form compounds.
• Atoms can be rearranged, combined, or separated in chemical reactions.
• Dalton based his theory on the law of conservation of mass and the law of constant composition.

Limitations of Dalton's Atomic Theory:

• Atoms consist of particles like electrons, protons, and neutrons but Dalton said atoms are indivisible and can neither be created nor be destroyed.
• The Discovery of isotopes revealed that the atoms of the same element possess different weights.

Thus, the indivisibility of matter was proposed by Dalton.

Additional Information

Rutherford:

• Ernest Rutherford gave his atomic model in 1911 after observing the gold foil scattering experiment.
• According to him, the positive charge and almost whole of the atomic mass is concentrated in the centre of the atom (as the nucleus).
• Electrons revolve around the nucleus in circular paths.

Bohr:

• In 1915, The Bohr model of the atom was proposed by Neil Bohr.
• Bohr's model explaining that electrons move in fixed orbitals.
• Bohr also explained that each orbit has a fixed energy level.

Einstein:

• Einstein was one of the famous scientists for his creative imaginations
• Albert Einstein was best known for his General and Special theory of relativity and the concept of mass-energy equivalence (E = mc2.)

Key PointsFerric sulfate:

• The chemical formula is Fe2 (SO4)3
• Ferric sulfate appears as a yellow crystalline solid or a greyish-white powder.
• The primary hazard is the threat to the environment.
• It is used for water purification and as a soil conditioner.

​Thus, the correct formula of Ferric sulphate is Fe2(SO4)3

Additional Information

FeSO4: Ferrous Sulphate

Fe(SO4)2: Compound does not exist

Fe3(SO4)2: Compound does not exist

Key Points

Calcium carbonate:

• Calcium carbonate is a chemical compound with the formula CaCO₃.
• It is a common substance found in rocks as the minerals calcite and aragonite (most notably as limestone, which is a type of sedimentary rock consisting mainly of calcite) and is the main component of eggshells, snail shells, seashells, and pearls.
• A limestone is a form of calcium carbonate.
• Other Different forms of calcium carbonate are Chalk and Marble.

Properties of Calcium Carbonate:

• Molar mass - 100.0869 g/mol.
• Odour - odourless.
• Appearance - Fine white powder; chalky taste.
• pH value - 9

Important Points

Molecular weight of CaCO_3​ = 40 + 12 + 3 × 16 = 100 gm

Mass of calcium in 1 mole of CaCO₃ ​= 40 gm

Percentage of calcium = (40/100) × 100 = 40%

Thus, the percentage of calcium in calcium carbonate is 40%

Key Points

Sound waves:

• Sound waves are mechanical waves, that is, they require a material medium to travel.
• It is the movement of the medium that transmits the wave.
• Since the density of solids is high and the molecules of a solid are closely packed, sound waves are quickly transmitted from one molecule to the next thus enabling it to travel faster.
• The speed of sound, therefore, is fastest in solids, followed by liquids (less dense than solids) and then gas (least dense).
• Sound cannot travel in a vacuum as there is no material medium.

Important PointsSpeed of Sound in Different Media:

• The speed of sound in the air is 331 m/s–1 at 0ºC and 344 m/s–1 at 22ºC.
• It depends on the type of medium through which it is travelling.
• It depends on the temperature and pressure of that medium.
• Speed of sound Decrease- when it passes from the solid to the gaseous state of a given medium.
• Speed of sound Increase- In any medium, when temperature and humidity increase.
• Speed of Sound- Solid > Liquid > Gases

​Thus, in solid medium sound travels faster.

Key Points

Light Year: 

• A light-year is a unit of distance.
• A light-year is a distance a beam of light travels in a single Earth year, or 6 trillion miles (9.7 trillion kilometres).
• One light-year is the distance travelled by light in a vacuum in one year.
• A light-year is a convenient unit of measurement of large distances.
• Generally, a light-year is used to represent astronomical distances.
• 1 light year = 9.46 × 1015 m = 9.46 × 1012 km = 9.46 × 1017 cm

Thus, one light-year is equal to all the above.

Important Points

Additional Information 

Parsec (parallactic second):

• It is the largest practical unit of distance used in astronomy.
• It is defined as the distance at which an arc of the length of 1 astronomical unit subtends an angle of 1 second of arc.
• 1 parsec = 3.08 × 1016 m

Astronomical unit:

• It is defined as the mean distance of the earth from the sun.
• It is used in astronomy to measure the distance of planets.
• 1 astronomical unit = 1 AU = 1.496 × 1011 m