Law of Conservation of Mass with Examples and Experiments
The conservation of mass is a fundamental principle in Physics and Chemistry. It states that the total mass of a closed system remains constant, regardless of the processes acting inside the system. In other words, mass can neither be created nor destroyed during any physical or chemical change. This law applies to all standard reactions and is frequently introduced in the early study of science.
Understanding the Conservation of Mass
When a chemical reaction or physical process takes place in a closed container, the total amount of matter before the change equals the total amount after. The substances involved may change their form or combine with each other, but the overall mass does not alter.
This concept is widely applicable, whether you are studying basic laboratory reactions or large-scale environmental processes. It ensures that calculations involving the mass of reactants and products can be reliably balanced in every scientific equation.
Key Concept Example
Suppose a reaction involves mixing chemical substances A and B in a sealed flask. When the reaction completes, the contents inside may look or behave differently, but the combined mass of the system—flask plus all its substances—does not change. This is a direct demonstration of mass conservation.
Applying Conservation of Mass: Stepwise Problem Approach
- Write down all reactants involved and their respective masses.
- List all products formed in the process.
- In a closed system, sum the masses of reactants and compare with the total mass of products.
- The masses must be equal, confirming the conservation of mass.
Example Table: Conservation of Mass in a Reaction
| Process | Mass Before (g) | Mass After (g) | Mass Change |
|---|---|---|---|
| Mixing two solutions in a closed flask | 100 | 100 | 0 |
| Heating a solid in a sealed container | 250 | 250 | 0 |
Formula for Conservation of Mass
The general mathematical statement for conservation of mass in a closed system is:
Total mass before = Total mass after
This can be applied to both chemical and physical changes as long as no mass escapes or enters the system.
Applications in Physics
Conservation of mass is used in solving numerical problems, balancing chemical reactions, and predicting behaviors in larger systems such as environmental cycles. It also supports the study of Laws of Motion and Thermodynamics where closed systems are regularly analyzed.
Practice Step: Example Problem
| Given | Required | Solution Steps |
|---|---|---|
| 30 g of substance X reacts with 70 g of Y | Total mass of produced substances |
Add masses:
30 g + 70 g = 100 g. Therefore, total mass after reaction = 100 g. |
Key Points to Remember
- The law of conservation of mass holds for all chemical and physical changes in a closed system.
- Any observed loss or gain of mass is usually due to an open system, where matter can enter or leave.
- Mastery of this law is essential for analyzing chemical reactions, environmental processes, and basic laboratory work.
Further Learning and Related Topics
- Study related laws such as conservation of energy and conservation of momentum.
- Review core concepts in basic laws of physics.
- Practice more numerical problems on conservation of mass.
Summary and Next Steps
- The conservation of mass forms the foundation of numerous topics in Physics and Chemistry.
- Understanding and applying this law helps in balancing equations and ensures consistency in experimental analyses.
- For deeper study, visit the Law of Conservation of Mass page and explore interactive sessions and practice questions provided by Vedantu.
FAQs on Law of Conservation of Mass: Explanation, Formula & Applications
1. What is the simple definition of the law of conservation of mass?
The law of conservation of mass states that the total mass of substances before and after a chemical reaction remains the same. In other words, mass is neither created nor destroyed during a chemical or physical change.
2. Who discovered the law of conservation of mass?
Antoine Lavoisier, a French scientist, is credited with discovering the law of conservation of mass in the late 18th century. His experiments demonstrated that the total mass in a closed system remains constant during chemical reactions.
3. What is the law of conservation of mass for kids?
The law of conservation of mass for kids means that the amount of stuff (mass) stays the same, even if it changes shape or form. Nothing gets lost or made from nothing during changes like melting, mixing, or reactions.
4. Why is mass conserved in a reaction?
Mass is conserved in a reaction because atoms are rearranged during chemical changes, but the total number and type of atoms stay the same. No atoms are lost or gained, so the overall mass remains constant.
5. State the law of conservation of mass with an example.
Law of conservation of mass: "In a closed system, the mass of reactants equals the mass of products."
Example: If 4g hydrogen reacts with 32g oxygen to form water, the water created will weigh 36g, showing that total mass is unchanged during the reaction.
6. What is the formula for the law of conservation of mass?
The formula is:
Total mass of reactants = Total mass of products
It is often written as:
mReactants = mProducts
7. How can the law of conservation of mass be demonstrated through an experiment?
The law can be shown by carrying out a chemical reaction in a closed container. For example:
- Weigh the sealed container with reactants before the reaction.
- Allow the reaction to happen without opening it.
- Weigh the container again after the reaction. The mass remains the same, proving mass conservation.
8. What is the difference between the conservation of mass and the conservation of energy?
Conservation of mass means total mass stays the same during changes, while conservation of energy means total energy in a system remains constant. Both are fundamental concepts but apply to different physical quantities.
9. Is the law of conservation of mass always valid?
The law of conservation of mass is valid for ordinary chemical and physical reactions in closed systems. However, in nuclear reactions or at speeds close to light, a small amount of mass can convert into energy, as described by Einstein’s equation (E=mc2).
10. In which types of chemical reactions does the law of conservation of mass apply?
The law applies to all chemical reactions and physical changes carried out in a closed system, including synthesis, decomposition, displacement, and combustion reactions.
11. What are some common misconceptions about the law of conservation of mass?
Common misconceptions include thinking that:
- Mass changes if substances change state.
- Mass can be lost as gas or gained as heat.
- The law does not apply if a new substance forms.
However, in every case, total mass is conserved in a closed system.
12. Why is the law of conservation of mass important for students?
The law is important because:
- It helps students understand chemical equations must be balanced.
- It is fundamental to Physics and Chemistry concepts for exams.
- It provides a foundation for solving numerical problems and understanding nature’s rules.
