In the some basic concepts of chemistry,we will study about importance of chemistry,what is difference between solids liquids and gases,properties of matter,some basic laws that applied in chemistry….etc
Importance of Chemistry
- • In meeting human needs for food, health care products and eduation other products required for improving quality of life.
- • In various areas such as weather patterns, functioning of brain and operation of a computer.
- • In chemical industries,factories…etc
Particles are held very close to each other in anfor more orderly manner with no freedom of movement.with a definite volume and shape.
Particles are close and can move around,with definite volume but no definite shape.
Particles are far apart and their movement is easy and fast.without any volume or shape
Properties of Matter
- Physical: Properties measured/observed without changing the identity or composition of substance. (Colour, odour)
- Chemical: Properties measured/observed when a chemical reaction occurs. for more FOR VIDEO
- (Acidity or Basicity, combustibility)
Measurement of Matter:
International System of Units (SI): (Length-m)
When the properties of a substance are studied, measurement is essential. The measurement system is done SI units (International System of Units).
Mass is the amount of matter present in a substance.
Weight is the force exerted by gravity on an object.
Uncertainty of measurement: Range of possible values within which the true,value of the measurement lies.
- Meaningful digits known with certainty.
- -Precision: Closeness of various measurements for same quantity.
- -Accuracy: Agreement of a particular value to true value of result.
Law of Conservation of Mass:
it states that matter can neither be created nor destroyed. proposed by Antoine Lavoisier.
Law of Definite Propportions:
A given compound always contains exactly the same proportion of
elements. proposed by Joseph Proust 1799
Law of Multiple Porportions:
This law states that If two elements can combine to form more than one
compound, the masses of one element that combine with a fixed mass of the other element are in ratio of small whole numbers. proposed by Dalton 1803 .
Gay Lussac’s Law of Gaseous Volume: Gay Lussac- 1808
When gases combine or all produced in a chemical reaction they do so in simple ratio by volume provided all gases are at same temperature and pressure.
Equal volumes of gases at the same temperature and pressure should contain equal number of molecules.
All these laws led to the Dalton’s atomic theory which states that atoms are building blocks of matter
(iii)Dalton’s Atomic Theory:
•Matter consists of in divisible atoms.
•All the atoms of a given element have identical properties including identical mass.
•Compounds are formal when atoms of different elements combine in a fixed rate.
•Atoms are neither created nor destroyed in chemical reaction Elements:Contains one type of particles i.e., atoms, molecules (fe,N)
- Compounds:Two or more atoms of different elements(H2,NH3)
- MIXTURES; TWO OR MORE SUBSTANCE PRESENT IN ANY RATIO
- Homogenous mixtures : Uniform composition (Sugar solution, air
- Hetrogenous: Non-uniform composition (Mixtures of salt and sugar
Atomic mass of an element is a number that expresses how many times the mass of an atom of the element is greater than 1/12th the mass of a C12 atom Molecular mass
The molecular mass of a molecule is obtained by taking sum of the atomic masses of different atoms present in a molecule
The amount of substance present in a given volume of a solution is expressed in number of ways, e.g., mass per cent, mole fraction, molarity and molality
mass per cent;It is the number of parts solute present in 100 parts by mass of solution.
Mole fration; It is the fraction of a particular component in the solution expressed in terms of mole.
Molarity;It is defined as the number of moles of solute dissolved per litre of solution
Molality; It is defined as the number of moles of the solute present per kilogram (kg) of the solvent
How To Determine Empirical and Molecular Formula:
- Step 1: Conversion of mass percent to grams.
- Step 2: Convert into number moles of each element.
- Step 3: Divide the mole value obtained above by the smallest number.
- Step 4: Write empirical formula by mentioning the number after writing
- the symbols of respective elements.
- Step 5: Writing molecular formula
(a) Determine empirical formula mass. Add the atomic masses
of various atoms present in the empirical formula.
(b) Divide molar mass by empirical formula mass.
(c) Multiply empirical formula by n obtained above.
Deals with the calculation of masses of the products and reactants involved in a reaction
How To Balance A Chemical Equation
- Step 1: Write correct formulas of reactants and products.
- Step 2: Balance number of C atoms.
- Step 3: Balance number of H atoms.
- Step 4: Balance number of O atoms.
- Step 5: Verify the number of atoms of each element