Chemical equations and balancing. Theory and practice with simulations

07/05/2026

The online simulations of chemical equations on this page will help you to better understand how chemical equations work and the laws that govern them. We will discover what a chemical equation is, what chemical formulas are and how the balancing a chemical equation can be done.

This Thematic Unit is part of our Chemistry collection

Chemical Equation

Symbolic representation of a chemical reaction showing the substances that react and those that are produced.

Equation Balancing

Process of adjusting coefficients so that the number of atoms of each element is equal on both sides of the equation.

Law of Conservation of Mass

Principle stating that in a chemical reaction the total mass of the reactants is equal to the total mass of the products.

Product

Substance formed as a result of a chemical reaction, written to the right of the arrow in the equation.

Reactant

Initial substance that participates in a chemical reaction and is consumed to form new products.

State of Matter

Notation in the equation (s, l, g, aq) indicating whether a substance is solid, liquid, gaseous, or in aqueous solution.

Stoichiometric Coefficient

Number placed in front of chemical formulas in an equation to indicate the relative proportion of molecules or moles.

Subscript

Small number indicating the amount of atoms of a specific element present in a molecule or compound.

What is a chemical equation

A chemical equation is a symbolic representation of a chemical reaction. These equations describe the changes that occur in the atoms and molecules of substances that are combining or decomposing during a reaction.

Chemical formulas

Chemical equations are written in the form of chemical formulas that represent the substances involved in the reaction. For example, the chemical equation for the combustion of methane is:

CH₄+ 2O₂ → CO₂ + 2H₂O

In this equation, CH4 represents methane, O2 represents oxygen, CO2 represents carbon dioxide, and H2O represents water. The numbers in front of the chemical formulas are the stoichiometric coefficients, which indicate the ratio in which the substances react and are produced.

Balancing a chemical equation

It is important to note that chemical equations must be balanced, that is, they must have the same number of atoms of each element on both sides of the equation. Balancing a chemical equation is done by adjusting the stoichiometric coefficients, ensuring that the law of conservation of matter is met.

Application of chemical equations and chemical formulas

Ultimately, chemical equations and chemical formulas are important tools for understanding how chemical reactions occur and for predicting the products of a reaction. They are also used to calculate the amount of reactants needed to produce a specific amount of product and vice versa.

Explore the fascinating world of chemistry with our online simulations of chemical equations. Adjust stoichiometric coefficients and observe the effects in real time to develop your chemistry skills and knowledge – learn in a dynamic and entertaining way!

Chemical Equation

Symbolic representation of a chemical reaction showing the substances that react and those that are produced.

Equation Balancing

Process of adjusting coefficients so that the number of atoms of each element is equal on both sides of the equation.

Law of Conservation of Mass

Principle stating that in a chemical reaction the total mass of the reactants is equal to the total mass of the products.

Product

Substance formed as a result of a chemical reaction, written to the right of the arrow in the equation.

Reactant

Initial substance that participates in a chemical reaction and is consumed to form new products.

State of Matter

Notation in the equation (s, l, g, aq) indicating whether a substance is solid, liquid, gaseous, or in aqueous solution.

Stoichiometric Coefficient

Number placed in front of chemical formulas in an equation to indicate the relative proportion of molecules or moles.

Subscript

Small number indicating the amount of atoms of a specific element present in a molecule or compound.

Explore the exciting STEM world with our free, online, simulations and accompanying companion courses! With them you’ll be able to experience and learn hands-on. Take this opportunity to immerse yourself in virtual experiences while advancing your education – awaken your scientific curiosity and discover all that the STEM world has to offer!

Simulations of chemical equations

Balancing a chemical equation

Watch the first of our simulations of chemical equations. How do you know if a chemical equation is balanced? What can you change to balance an equation? Play a game to test your ideas!

Reactants, products and leftovers

Create your own sandwich and then see how you can make many sandwiches with different amounts of ingredients. Do the same with chemical reactions. See how many products you can make with different amounts of reactants, products and leftovers Can you get a perfect score on each level?

Law of Definite Proportions

The law of definite proportions, also known as the law of constant proportions, is one of the fundamental principles of chemistry. It states that in a chemical compound, the elements are always present in a fixed and definite proportion in terms of their mass. For example, in water (H2O), the ratio of hydrogen to oxygen by mass is always 2:16, or in terms of atoms, there are always two hydrogen atoms for every oxygen atom.

Observe in this simulation how in a reaction between hydrogen and oxygen. In a reaction between hydrogen and oxygen to form water, two atoms of hydrogen combine with one atom of oxygen to form a water molecule. Hydrogen and oxygen always react in a 2:1 ratio to form water.

Giants of science

“If I have seen further, it is by standing on the shoulders of giants”

Isaac Newton

John Dalton

1766

–

1844

John Dalton formulated the first atomic theory, explaining the composition of matter and the law of multiple proportions in chemical compounds.

“Science is the foundation of truth”

Marie Curie

1867

–

1934

Marie Curie discovered the elements polonium and radium, introduced the concept of radioactivity, and pioneered nuclear chemistry, demonstrating that atoms were not indivisible

“In life, there is nothing to be afraid of, only to understand”

Become a giant

Your path to becoming a giant of knowledge begins with these top free courses

Free mode

Basic Steps in Magnetic Resonance

Free mode

Basic Analytical Chemistry

Free mode

Big Bang and the Origin of Chemical Elements

Free mode

Preparing for CLEP Chemistry: Part 1

Free mode

Pre-University Chemistry

Professional development for Educators

Your path to becoming a giant of knowledge begins with these top free courses

Free mode

HP Digital Skills for Educators – Google Workspace

Free mode

Teaching with Physical Computing: Practical application and classroom strategies for PBL

Free mode

Teach kids computing: Developing your programming pedagogy

Free mode

Teach teens computing: Databases and SQL

Giants of science

“If I have seen further, it is by standing on the shoulders of giants”

Isaac Newton

Marie Curie

1867

–

1934

Marie Curie discovered the elements polonium and radium, introduced the concept of radioactivity, and pioneered nuclear chemistry, demonstrating that atoms were not indivisible

“In life, there is nothing to be afraid of, only to understand”

Fritz Haber

1868

–

1934

Fritz Haber developed the Haber-Bosch process, enabling large-scale ammonia synthesis, revolutionizing fertilizer production and industrial chemistry

“Chemistry has the power to transform life on Earth”

Become a giant

Your path to becoming a giant of knowledge begins with these top free courses

Free mode

Basic Steps in Magnetic Resonance

Free mode

Basic Analytical Chemistry

Free mode

Big Bang and the Origin of Chemical Elements

Free mode

Pre-University Chemistry

Free mode

Preparing for CLEP Chemistry: Part 1

Professional development for Educators

Your path to becoming a giant of knowledge begins with these top free courses

Free mode

Teach kids computing: Programming

Free mode

Teach computing: Physical computing with Raspberry Pi and Python

Free mode

Teaching with Physical Computing: Practical application and classroom strategies for PBL

Free mode

Teach teens computing: Encryption and cryptography

Test your knowledge

What is a chemical equation and what is it used for?

A chemical equation is a symbolic and concise representation of a chemical reaction in which formulas are used to show which substances react (reactants) and which substances are formed (products), connected by arrows indicating the direction of the process and accompanied by coefficients that ensure the number of atoms of each element is conserved during the change. This is essential because chemical equations not only organize and describe what happens during a reaction, but also allow calculations of amounts of reactants and products, help understand how chemical bonds are transformed, and predict behaviors in experiments or industrial processes without having to describe every detail in words.

How is a chemical equation balanced and why is it important?

Balancing a chemical equation means adjusting the coefficients of reactants and products so that the number of atoms of each element is the same on both sides of the equation, which is fundamental because the law of conservation of mass states that atoms are neither created nor destroyed in a chemical reaction, only rearranged. Balancing ensures that the equation respects this natural law, allowing an accurate representation of how substances interact and guaranteeing that any further calculations, such as determining how much of a reactant is needed or how much product is formed, are based on a correct and reliable depiction of reality.

Why isn’t it enough to just write the formulas without balancing them?

It might seem that writing the formulas of reactants and products is enough to describe a reaction, but if the equation is not balanced, it represents something that physically cannot happen because one of the basic principles of chemistry is that matter is not lost or gained during a reaction. Adjusting the coefficients to equalize the number of atoms of each element ensures a faithful description of the actual process, which in turn allows any predictions or calculations to be made on a correct basis, because without balancing, the results would not make sense in terms of quantities or the energy involved.

What if I struggle to find the right coefficients when balancing, is there a step-by-step way?

At first, finding the correct coefficients for a chemical equation can be confusing, but a common strategy is to identify the elements that appear in the fewest places and balance them one by one, adjusting coefficients gradually so that changing one does not unbalance others already balanced, and finally checking that all atoms are balanced. With practice and patience, this process becomes more intuitive, and by focusing on one element at a time and reviewing changes step by step, students develop a deeper understanding of how the amounts of reactants and products are related in a reaction.

If everything is balanced and the formulas are correct, does that mean the reaction will definitely occur?

Not necessarily, because having a balanced equation and correct formulas is an essential part of describing how matter transforms, but it does not guarantee that the reaction will happen spontaneously under given conditions. For a reaction to take place, factors such as activation energy, temperature, the presence of catalysts, or the physical compatibility of reactants also play a role, so while the equation provides an accurate and balanced description, the actual experiment or system may require specific conditions for the transformation to occur in reality.