Anything that has mass and occupies a volume in space is called matter. It is classified into three phases.

• Solid:

Substances with definite shape and volume and the particles with the least freedom of movement are called solids. Examples: wood, glass, iron

• Liquid:

Substances with a definite volume but no definite shape are liquids. They possess the property of flowing or can be poured. Examples: water, milk, alcohol

• Gas:

Substances with no definite volume or shape are gases. They completely fill the container they are stored in and can be compressed. Examples: oxygen, hydrogen

Classification of Matter at Macroscopic Level

At bulk or macroscopic level, matter can be classified as follows:

• Mixtures: 

Mixtures are substances formed when two or more compounds are mixed in any ratio. There are two types:

Homogeneous mixture: When two or more substances are mixed to form a mixture in such a way that the composition of the mixture is uniform, then it is called a homogenous mixture. Example: solution of sugar and water. 

Heterogenous mixture: When two or more substances are mixed in a way that the resulting mixture has a non-uniform composition, then it is a heterogeneous mixture. Example: sand and camphor.

• Pure substances: 

A substance containing only one type of particle is called pure. They are categorised as follows: 

Element: A pure substance that contains only one kind of atom and cannot be further simplified is called an element. They can be metals, non-metals, or metalloids. 

Compound: A compound is a pure material that contains two or more elements mixed in constant proportion.

Each substance shows its unique and characteristic properties. These are divided as follows.

• Physical properties: 

The properties observed without changing the composition of the substance. For example, odour, density, and boiling point.

• Chemical properties:

The properties that can only be observed under chemical reactions. For example acidity and basicity.

Measurement

• Physical Quantities: 

They are measured in two parts: the number and unit. 

SI Units: 

The International System of Units has set seven fundamental scientific quantities. These include:

• Length: metre (m)
• Mass: kilogram (kg)
• Time: seconds (s)
• Electric Current: ampere (A)
• Thermodynamic Temperature: kelvin (K)
• Amount of substance: mole (m)
• Luminous Intensity: candela (cd)

Some Important Definitions

• Mass: 

The amount of substance present is called mass. SI unit: kilogram 

Weight: The force exerted by gravity on an object because of its mass. SI unit: newton

• Volume: 

The three-dimensional space surrounded by closed boundaries that is occupied or contained by a substance. SI unit: meter cube

• Density:

Density is mass per unit volume. SI unit: kg m³

• Temperature: 

The measure of hotness or coldness. SI unit: K

• Law of conservation of mass

Given by Antoine Lavoisier, the law states that in a chemical reaction, the mass of reactants is equal to the mass of products formed.

• Law of constant proportions

Given by Joseph Proust, the law states that in a compound, the mass proportions of the elements are always the same.

• Law of multiple proportions

Proposed by Dalton, the law states that when two elements combine to form more than one compound, then the weight of one element is proportional to the fixed weight of the other element and that a ratio is a whole number.

• Law of reciprocal proportions

Given by Richter, the law states that if two elements combine with a fixed mass of the third element, then the ratio of combined mass will be constant.

• Gay Lussac’s Law of Gaseous Volumes

It states that the relationship between the volume of a gaseous reactant and the product is a simple whole number.

• Avogadro Law

According to Avogadro, an equal volume of gases at the same temperature and pressure will have the same number of molecules.

Postulates of Dalton’s Atomic Theory released in 1808:

• All matter is made of indivisible atoms. 
• Atoms of a given element will have identical properties. Atoms of different elements will have different properties. 
• Atoms combine in a fixed, simple ratio to form compounds. 
• Atoms can neither be created nor be destroyed.

Atom 

Atom is the smallest unit that shows the properties of an element. The mass of an atom is defined in units of AMU. 1 AMU is equal to one-twelfth of the mass of C-atom. 

Molar atomic mass is the mass (in grams) of 6.022 x 10^23 atoms. This number is called Avogadro’s number.

Molecule

The molecule is the smallest unit of a substance that shows the physical and chemical properties of the substance. The molecular mass can be found by adding the atomic mass of each atom that constitutes the molecule.

Chemical Reaction 

The process of rearranging the molecular or ionic structure of a substance and the change differs from that which occurs in a physical or nuclear reaction is a chemical reaction. Chemical reactions must be balanced when written.

Stoichiometry 

Stoichiometry is the study of chemical reactions and calculations related to it. The stoichiometric coefficient is used to balance the equations.

Percent Yield 

Percent yield is the relationship between the amount of product formed and the amount of product predicted. 

Percentage yield = Actual Yield/Theoretical yield x 100

Reactions in Aqueous Media 

Two solids cannot react with each other in the solid-state. Thus, they are dissolved in liquid. The solution formed includes a solvent and a solute. The strength of the solution depends upon the concentration of solute present per unit solvent. Molarity and molality are commonly used to define the strength of a solution.

Dilution Law 

The number of moles present in the solution does not change even if its concentration is changed. 

M1V1 = M2V2

Effect of Temperature 

As the temperature increases, the volume of solvent also increases. There is no effect on the strength of the solution if the temperature is raised in a closed system.

The concept of equivalence is used to simplify understanding chemical reactions.

• Equivalent mass: 

The mass of an acid or base that has 1 mol of H+ or OH - ion is equivalent mass.

• Valence factor: 

The number of H+ or OH - ions present in 1 molecule or mole of acid of base.

• Equivalents: 

Number of equivalents if the ratio of the weight of acid and base taken is divided by the equivalent weight.

Mixture of Acids and Bases

When mixing acids and bases, the mixture can be acidic or alkaline based on the strength of the acid and base mixed.

Law of Chemical Equivalence 

The law states that an equivalent of a reactant is combined with an equivalent of another reactant to get an equivalent of each product. Thus, 

aA + bB\( \rightarrow \) cC + dD

Equivalent Weights of Salts 

The mass of cation divided by the charge on it will give the equivalent mass of cation. Similarly, the mass of an anion divided by its charge is the equivalent mass of the anion. These are used to calculate the equivalent weight of a compound that is neither base nor acid.

Origin of Equivalent Concept 

Equivalent weight was previously defined as the weight of the element combined with 1 gram of hydrogen. It was then changed to the weight of the element combined with 8 grams of oxygen. The equivalent weight of an element depends on its charge.

Equivalent Volume of Gases 

It is the volume occupied by 1 equivalent of a gas at STP. The equivalent mass of a gas is given by the ratio of molecular mass by atomic number. 1 mole of gas occupies 22.4 L of volume at STP.

Normality

The normality of a solution is the number of equivalents of solute present in 1 L of solution. 

N = equivalent of solute/volume of solution in L.

What are the topics in basic concepts of chemistry?

The topics include atom, molecule, equivalent concept, stoichiometry, the law of chemical combination, and more.

Are learning Some basic concepts of chemistry important? 

Yes, as the chapter goes over the most fundamental concepts of chemistry, it is important.

What are the two important basics of chemistry?

The two essential basics of chemistry are experiment and observation.