Understanding Chemical Reactions and Matter Transformation

Physical and Chemical Changes

Physical changes do not cause new substances to appear. However, chemical changes produce substances that were not present before the transformation, as a result of a chemical change.

Reagents and Products in a Chemical Reaction

Reagents are the pure substances that are combined together in order to produce a chemical reaction. Products are the substances produced as a result of combining reagents in order to produce a chemical reaction.

Characteristics of Chemical Changes

• Energy is exchanged throughout the course of a chemical reaction.
• Reversible and irreversible reactions.
• The states of aggregation.

Collision Theory in Chemical Reactions

According to collision theory, chemical reactions take place because the molecules in reagents bump into one another with so much energy that they break the bonds between the reagent atoms.

The Rate of Chemical Reactions

The rate of a chemical reaction is quantified by observing how the amount of product increases in a certain amount of time.

Factors Influencing Chemical Reactions

Temperature: When temperature is increased, the molecules have more energy.

Writing Chemical Reactions

Chemical equations use symbols to explain a chemical reaction in a chemical formula.

Atomic Reordering in Chemical Reactions

In a chemical reaction, the atoms in the reagent elements are reordered and form different bonds.

Balancing Chemical Equations

To balance a chemical equation, the stoichiometric coefficients of each substance must be adjusted.

Fundamental Laws in Chemical Reactions

According to the Law of Conservation of Mass, matter cannot be created or destroyed in a chemical reaction. In other words, the collective mass of the products is equal to the collective mass of the reagents.

Fixed Proportions in Chemical Reactions

In chemical reactions, the proportion by mass of the substances involved in the reaction is fixed, regardless of the quantity of each substance available.

Amount of Substance and Chemical Reactions

The amount of a substance in moles tells us how many units there are in a certain portion of a substance, regardless of the mass of these units.

The amount of substance is measured in moles, which are defined as the amount of substance that contains the same number of entities.

The molar mass of a substance is the mass expressed in grams of one mole of said substance.