Evidences & Symbols of Chemical Reactions - 1st Sem Chemistry

Physical charge

A change in physical properties where there is no formation of a new substance.

Chemical change

A change in matter that produces one or more new substances. Also known as chemical reaction.

Reactants

A starting substance in a chemical reaction.

Products

The different substances produced by a chemical reaction.

Phase change

A change from one state to another without a change in chemical composition.

Production or absorption of heat and light; Evolution of gas; Formation of precipitate; Change in temperature/color; Production of mechanical energy; Production of sound

Enumerate seven (7) evidences of chemical reaction:

Production or absorption of heat

Formation of sparks or flame or light.

Exothermic

Warming the surrounding.

Endothermic

Cooling the surrounding.

Evolution of gas

Formation of bubbles.

Formation to precipitate

Insoluble (cannot be dissolved) solid is formed.

Word equation

An equation in which the reactants and products in a chemical reaction are represented by words.

+

Written between symbols and/or formulas of reactants or products.

→

"Yields," separates reactants from products.

⇌

Used in place of → for reversible reactions.

(s); (l); (g)

Designates a reactant or product in the solid state, liquid state, or gaseous state; placed after the formula.

(aq)

Designates an aqueous solution; the substance is dissolved in water; placed after the formula.

Δ

→

/

heat

→

Indicates that heat is supplied to the reaction.

Pt

→

A formula written above or below the yields sign indicates its use as a catalyst (in this example, platinum).

H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂

Enumerate seven (7) diatomic molecules:

CₙH₂ₙ+2

State the formula for fuel (alkanes), where n = any integer:

Methane

CH₄

Ethane

C₂H₆

Propane

C₃H₈

Butane

C₄H₁₀

Pentane

C₅H₁₂

Hexane

C₆H₁₄

Heptane

C₇H₁₆

Octane

C₈H₁₈

Nonane

C₉H₂₀

Decane

C₁₀H₂₂