What is chemistry?
Chemistry is a branch of science that deals with the study of the composition, structure & properties of matter.
List out the important branches of chemistry
1) Physical Chemistry 2) Inorganic Chemistry
3) Organic Chemistry 4) Analytical Chemistry.
Importance of chemistry
- Chemistry plays an important role in providing food, cloth & shelter.
- It plays an important role in the production of many lives saving drugs.
- It plays an important role in the manufacture of fertilizers, insecticides & pesticides.
- It plays an important role in controlling pollution.
- It plays an important role in the production of superconducting ceramics, polymers, optical fibers, etc.,
Matter
Anything which has mass & occupies space. It can exist in three physical states i.e. Solid, liquid & gas. It is classified as a Pure substance & Mixture.
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General characteristics of solid, Liquid & gases
Solid
The particles are held close to each other & there is no freedom of movement. They have definite shape & definite volume.
Liquid
The particles are close to each other, but they can move around. They have definite volume but do not have a definite shape.
Gases
The particles are far apart & their movement is easy & fast. They do not have definite volume & definite shape. They completely occupy the container in which they are placed.
Mixture
A mixture is the physical combination of two or more substances in which the identities are retained. It is again classified as Homogeneous & Heterogeneous mixtures.
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Homogeneous Mixture
A mixture of two or more components forming a single phase & composition is uniform throughout.
Ex: sugar solution in water.
Heterogeneous Mixture
This is a mixture in which the composition is not uniform throughout.
Ex: Water & oil.
Pure Substance
A substance that has a fixed( definite & Constant) chemical composition throughout with definite chemical properties. It is further classified as an element & compound.
Elements
An element consists of only one type of atom.
Compounds
This is formed by the combination of two or more elements in a fixed & definite ratio.
Ex: HNO3
Properties of Matter
It is classified as physical properties & Chemical properties.
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Physical Properties
This can be measured or observed without changing the composition of the substance.
Ex Colour, Odour, melting point, boiling point, density, etc.,
There are seven basic physical quantities.
Chemical Properties
Basic Physics Quantities
| Physical Quantity | Name of the unit | Symbol |
| Length | meter | m |
| Mass | kilogram | kg |
| Time | second | s |
| Temperature | kelvin | K |
| Electric Current | ampere | A |
| Luminous Intensity | candela | cd |
| Amount of substance | mole | mol |
Multiples & prefixes used in the SI system
Length (Meter): It is equal to the distance traveled by light in a vacuum in ¹/₂₉₉,₇₉₂,₄₅₈ second. (300,000,000)
Mass (Kilogram): It is equal to the mass of the international prototype of the kilogram.
Time(Second): It is defined in terms of the radiation frequency at which atoms of the element cesium change from one state to another.
Ampere: The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2 X 10-7 N.
Kelvin: The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.
Amount of Substance: The mole(mol) is the amount of substance of a system that contains as many elementary entities as there are atoms in 0.012 kilograms of carbon12.
Luminous intensity: The candela is the luminous intensity. In a given direction, of a source that emits monochromatic radiation of frequency 540 X 1012 hertz & that has a radiant intensity in that direction of 1/383 watt per steradian.
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What is the mass of a substance?
The amount of matter present in a substance.
What is the weight of a substance?
The force excreted by gravity on an object.
| Mass | Weight |
| The mass of a substance is constant | The weight of the substance varies from place to place ( it depends on gravity) |
| Mass is a scalar quantity | Weight is a vector quantity |
SI Unit
Volume
cm3 or dm3 1L =1000mL., 1000cm3=1dm3 or 1L, cm3 =mL
Density
kgm-3 , CGS gcm-3
Temperature
- Degree Celsius (oC).
- Degree Fahrenheit
- Kelvin (K)-SI unit
Relation between oF to oC:
Relation between oC to Kelvin: K = oC + 273.15.
Scientific Notation
Scientific notation is a way of expressing numbers that are too large or too small to be conveniently written in decimal form.
Precision
Refers to the closeness of various measurements for the same quantity.
Accuracy
Is the agreement of a particular value to the true value of the results.
| Measurements / g | ||||
| Student A | 1.95 | 1.93 | 1.940 | Precision |
| Student B | 1.94 | 2.05 | 1.995 | Nor Precision & Accuracy |
| Student C | 2.01 | 1.99 | 2.000 | Precision & Accuracy |
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What are significant figures? Give the general rule.
Significant figures are meaningful digits that are known with certainty.
- All non-zero digital are significant (Noteworthy or having a particular meaning).
- Zeros proceeding to the first non-zero digit (leading zeros) are not significant.
- Zeros between two non-zero digits are significant.
- Zeros at the end or right of a number (trailing zeros) are significantly provided they are on the right side of the decimal point.
- When the numbers are written in scientific notation the number of digits between 1 & 10 gives the number of significant figures.
- Round Off: Rounding off means a number is made simpler by keeping its value intact but close to the next number.
- Rules for rounding the numbers
- If the rightmost digit to be removed is more than 5, the preceding number is increased by one.
Ex 2.359 = 2.36, ( 5 is the preceding number)
- If the rightmost digit to be removed is less than 5, the preceding number is not changed.
Ex: 2.344 =2.34.
- If the rightmost digit is to be removed is 5 the preceding number is not changed if it is an even number but it is increased by one if it is an odd number.
Ex 6.35 =6.4, 6.25 = 6.2
What is the dimensional analysis Factor label method or unit factor method
The method used to convert units from one system to other while solving problems.
1 inches = 2.54 cm
State law of Conservation of Mass by Antoine Lavoisier
It states that matter can neither be created nor destroyed.
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Law of definite proportions by Joseph Proust
A given compound always contains exactly the same proportion of elements by weight.
Law of multiple proportions by Dalton
If two elements can combine to form more than one compound, the masses of the one element that combine with a fixed mass of the other element are in the ratio of the small whole number
Ex H2 (2g) + O2 (16g) H2O ( 18g)
Ex H2(2g) + O2 ( 32 g) H2O2 ( hydrogen peroxide)
The mass of oxygen ( 16 g and 32g ) combined with a fixed mass of hydrogen (2g) bears a sample ratio (16:32 or 1:2).
Law of gaseous Volumes by Gay lussac
When gases combine or are produced in a chemical reaction they do so in a simple ratio by volume provided all gases are at the same temperature & pressure.
H2 (100g) + O2 (50g) gives H2O (100g) (Hydrogen & oxygen ratio is 2:1).
Avogadro Law by Avogadro
An equal volume of gases at the same temperature & pressure should contain an equal number of molecules.
Dalton’s Theory
- The matter is made of atoms, which are indivisible.
- All atoms of a given element are identical in mass and properties.
- Compounds are combinations of two or more different types of atoms.
C + O ————-> CO (1:1).
- The chemical reaction is a rearrangement of atoms.
Molecular Mass
Molecular mass is the sum of the atomic masses of the elements present in a molecule. Ex: CH4 : ( 1 X 12.011) + (4 X 1.008) = 16.043u
Formula Mass
Formula mass is the sum of the atomic weight of the atoms in the empirical formula of the compound.
NaCl crystal contains huge numbers of Na & Cl. ( 23.0 + 35.5 =58.5u).
( Ionic compound is not a molecule, NaCl crystal contains an equal number of cations & anions They exist in a 1:1 ratio, so the empirical formula is one).
Formula mass is used in ionic solids instead of molecular mass. Why?
Because ionic solids do not exist as a single entity in the solid state.
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Atomic mass
It is defined as the mass exactly equal to 1/12th the mass of one atom of carbon-12 isotopes.
Note: Avogadro ’s number = 6.022 X 1023
Molar Mass
The mass of one mole of a substance in grams is called its molar mass.
Molar Volume
The volume occupied by one mole of gas at STP is called molar volume.
Molar Mass of water=18.02 gmol-1
Molecular Mass
Is the mass of one molecule of a substance expressed in unified mass (u).
Empirical Formula
It is the simplest formula that represents the simplest whole number ratio of various atoms present in a compound.
(C6H12O6– Empirical formula of glucose: CH2O i.e 1:2:1 Ratio)
Molecular Formula
It gives the kind and number of atoms of each element present in the molecule of a compound.
Molecular Formula – C6H12O6.
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Stoichiometry
Stoichiometry deals with the calculation of masses (sometimes volumes also) of the reactants and the products involved in a chemical reaction.
Limiting Reagent
It is defined as the reagent which is completely consumed during the reaction and is called the limiting reagent.
Excess Reagent
The reagent that is not completely consumed in a chemical reaction is called excess reagent.
Reaction in solution
Most of the reactions are carried out in a solution state. The concentration of a solution or the amount of substance present in its given volume can be expressed in any of the following ways.
- Mass percent or Weight percent
- Mole fraction
- Molarity
- Molality.
Mass Percentage
Mole Fraction
It is the ratio of the number of moles of a particular component to the total number of moles of the solution.
Molarity
It is defined as the number of moles of the solute in 1 liter of the solution.
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Molality
It is defined as the number of moles of solute present in 1kg of solvent.
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- THERMODYNAMICS
It is the branch of physics that deals with the concepts of heat and temperature and the inter conversion of heat and other forms of energy. - THERMAL PROPERTIES OF MATTER
Temperature is a relative measure or indication of the hotness or coldness of a body. The temperature of a body determines the direction of the flow of energy. The SI unit of temperature is kelvin (K). °C is a commonly used unit of temperature. - MECHANICAL PROPERTIES OF FLUIDS – PART 2
The viscous drag increases with increases velocity of the body, but it is found that the body after attaining certain velocity starts moving with a constant velocity called terminal velocity. - MECHANICAL PROPERTIES OF FLUIDS – PART 1
The materials that can flow are called fluids. Liquids and gases are collectively known as fluids. Unlike a solid, a fluid has no definite shape of its own. - MECHANICAL PROPERTIES OF SOLIDS
The property of a body, due to which it tends to regain its original size and shape when deforming force is removed, is called elasticity. The deformation caused is called as elastic deformation.
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