Must see the chart
Homogeneous mixture-Material said to be homogeneous if it has uniform composition and identical properties throughout or a material is said to be homogeneous. Heterogeneous mixture- A material is said to be heterogeneous if it consists of a number of phases are separated from each other by distinct boundaries. Atoms-An atom is the smallest particles of an element which may or may not be capable of independent existence. Example- atom of iron,silver,gold Molecules-A molecule is the smallest particles of an element or a compound which can exist freely. Molecules may be classified into two types.
1. Molecules of elements- They are made of only one kind of atom .they are called homoatomic or homo nuclear molecules. 2.The atomicity of metal elements like sodium, magnesium, aluminium etc..is taken as monoatomic molecules. 3.hydrogen Nitrogen, oxygen,clorine,bromine, etc.. have two atoms in their molecules . So the atomicity is 2.They are called as diatomic molecules. 4.Ozon has 3 atom in its molecules,so the atomicity is 3 .They are called as triatomic. 5.phosphorus has 4 atom in its molecules,so the atomicity is 4 .They are made up atoms of different elements and hence are called heteroatomic or heteronuclear molecules.They may be dioatomic,tetraatomic, depending upon the name of atoms present in a molecules of the compound. Ex-HCL,water, carbon dioxide, ammonia,methen,etc..... Physical properties-Physical properties are those which can be measured or observed without changing the identity or composition of the substance. Example-mass, volume, melting point, boiling point Chemical properties- Chemical properties are those in which a chemical change in the substance occurres.
The measurements of any physical quantities consists of two parts. a.The number b.The unit Example-its an object weight 4.5 kg It involves two parts 4.5 is the number and kg is the unit.
~ A unit is defined as the standards of reference choosen to measure any physical quantities. ~In metric system the differents units of a physical quantity are related to each others as multiples of power of 10 Example-The improve system of units has been accepted international system SI units or in sorts SI units.
Seven basic units(must learn)
Measurements of temperature- There are 3 scale of temperature : 1.Degree celsius 2.Degree Fahrenheit 3.kelvin
Measurements of volume- The SI unit of volume is m^3 1L=1000 ml 1L=100 dm^3 1m^3=100(cm)^3=10^3 L
Measurements of mass- Mass is the quantity of Matter contained in the sample and for the given sample it is constant and it's it's doesn't depend upon the palace.
Weight is the force with which the body is attracted towards the earth it depends upon the acceleration due to gravity which varies from place to place .The mass of a substance can be determined very accurately in the laboratory by using analytical balance . SI unit of mass is kilograms 1kg=1000g
Unit of length...The SI unit of length is metre. It is also expressed in angstrom or nanometres or picometre.
Accuracy of measurement-The accuracy of any measurements depends upon the 1.accuracy of the measuring device used. 2.The skill of its operator .
If the average value of differents measurements is closed to the correct value the measurements is said to be accurate.
If the value of different measurements are closed to each other and hence close to the average value,the measurement is said to be precise. A measurement can have a good accuracy but poor precision because different measurement may give a correct average. Error is measurement when the same mistake is made repeatedly are called systemic error. They don't effect the precision but they often affect the accuracy of measurement . Significant figure-The total number of digits in a number including the last digits whose value is uncertain is called the number of significant figures. Rules for determining the number of significant figures..1.all non-zero digits as well as the zeros. Between non-zero digits are significant. 573 has three significant figures 5004 has 4 significant figures. 0.49 has three significant figures.
2.zero to left of the first non-zero digits in a number are not significant. 0.05 has 1 significant figures. 0.0045 has two significant figures.
3.If a number ends in zero but these zeros are to the right of the decimal point then these zero are significant. 5.0metre has two significant figures. 2.500 has two significant figures. 0.0200has three significant figures.
4.It a number ends in zero but these zeros not to right of a decimal point,these zeros m inay be significant. 1.05×10^3 has four significant figures 1.060×10^3has four significant figures. Mathematical operations on numbers expressed in scientific rotation...1)4567.654 will be written as 4.683507×10^3
Decimal is moved three places towards left and that only one non-zero digits is left and number of places moved is the exponent of 10 in scientific rotation.
2)0.000256 will be written as 2.56×10^-4
Decimal is moved four places towards right so that there is only non-zero digits before the decimal point of 10 in -4 .
Calculation and involving multiplication & division in multiplication the coefficient I.e. The factor 10^n are multiplied and the exponents of 10 and added up. Example-(5.7×10^6) (4.2×10^5) =(5.7 ×4.2) (10^6+5) =23.94×10¹¹
Indivision the factor N are divided and exponent are subtracted . Example-(5.7×10^6)÷(4.2×10^3) =(5.7÷4.2)×(10^6-3) =1.357×10^3
In addition and subtraction 1st number are written in such a way that they have the same exponents.Talkingout 10^n common. The coefficients are added or subtracted. Example-4.56×10^3 + 2.62×10^2 =45.6×10^2+2.62×10^2 =(45.6+2.62)×10^2 =58.22×10^2
Rules for determining the number of significant figures.....Rule1.the result of an addition or subtraction should be reported to the same number of decimal point as that of the term with least num.of decimal places. Example-4.523+2.3+6.24 Actual sum=13.063 Reported sum=13.1 4.523has 3 decimal places. 2.3 has 1 decimal places 6.24 has 2 desimal places.
Answer should be reported only up to one decimal places.
Example- 18.4215-6.01 Actual difference- 12.4115 Reported difference- 12.41 As the second number has 2 decimal places only the answer is reported up to two decimal places.
Rule2.the result of a multiplication or division should be reported to the same number of significant figures as is possessed by the least precise term used in calculation. Example-4.327×2.8 Actual product- 12.1156 Reported product- 12
The 1st num.has 4 significant figures while the 2nd has 2. The actual product has been rounded of to give a reported product, containing two significant figures. Example- 0.46÷15.734 Actual quotient- 0.029236 Reported quotient- 0.029
It should contain only significant figures .
Rule3.If a calculation involved a number of steps the results should contain the same number of significant figures as that of the least precise.number involved,other than the exact number. (42.967×0.02435)÷(0.34×4) =0.7692988 =0.77
Thanks for viewing,this is part one of "some basic concepts of chemistry" I'll try to publish next part soon🙏🙏Thanks for visit🙏🙏
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Nice sir
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