Uploaded August 2025 | Updated September 2026, 1 week ago
Laws of Conservation of Mass and Constant Composition Explained
Dr. DeBacco
Law of Conservation of Mass
Lavoisier- “Father of Chemistry”
Matter cannot be created or destroyed during a chemical reaction; it is only rearranged.
The total mass of reactants in a chemical reaction equals the total mass of the products
Assuming provided the reaction occurs in a closed system where no matter is added or removed
Law of Conservation of Mass
When 12 g of carbon reacts with 32 g of oxygen to form carbon dioxide (CO₂), the resulting CO₂ has a mass of 44 g
12 g Carbon + 32 g Oxygen = 44 g Carbon dioxide
Conserving the total mass
Law of Constant Composition
Law of Constant Composition, also known as the Law of Definite Proportions, states that a chemical compound always contains the same elements in the same fixed proportions by mass, regardless of the source or method of preparation.
This means the ratio of the masses of the elements in a compound is constant.
Law of Constant Composition
Fixed Ratios: For example, water (H₂O) always has hydrogen and oxygen in a 2:1 ratio by molecule count, or approximately 1:8 by mass (11.19% hydrogen, 88.81% oxygen), whether it’s from a river, lab, or ocean
Link to Lecture Slides: drive.google.com/file/d/1S0rpNq-X8n3PWYWwdpT017gGlCI6Lfan/view?usp=drive_link
*Due to the description character limit the full work cited for "Laws of Conservation of Mass and Constant Composition Explained" can be viewed at... docs.google.com/document/d/1BLxq4tEEbfkCL1ml_n7WCi9f_o_yAq3w/edit?usp=drive_link&ouid=104237452697237972847&rtpof=true&sd=true
Laws of Conservation of Mass and Constant Composition Explained
Dr. DeBacco
Law of Conservation of Mass
Lavoisier- “Father of Chemistry”
Matter cannot be created or destroyed during a chemical reaction; it is only rearranged.
The total mass of reactants in a chemical reaction equals the total mass of the products
Assuming provided the reaction occurs in a closed system where no matter is added or removed
Law of Conservation of Mass
When 12 g of carbon reacts with 32 g of oxygen to form carbon dioxide (CO₂), the resulting CO₂ has a mass of 44 g
12 g Carbon + 32 g Oxygen = 44 g Carbon dioxide
Conserving the total mass
Law of Constant Composition
Law of Constant Composition, also known as the Law of Definite Proportions, states that a chemical compound always contains the same elements in the same fixed proportions by mass, regardless of the source or method of preparation.
This means the ratio of the masses of the elements in a compound is constant.
Law of Constant Composition
Fixed Ratios: For example, water (H₂O) always has hydrogen and oxygen in a 2:1 ratio by molecule count, or approximately 1:8 by mass (11.19% hydrogen, 88.81% oxygen), whether it’s from a river, lab, or ocean
Link to Lecture Slides: drive.google.com/file/d/1S0rpNq-X8n3PWYWwdpT017gGlCI6Lfan/view?usp=drive_link
*Due to the description character limit the full work cited for "Laws of Conservation of Mass and Constant Composition Explained" can be viewed at... docs.google.com/document/d/1BLxq4tEEbfkCL1ml_n7WCi9f_o_yAq3w/edit?usp=drive_link&ouid=104237452697237972847&rtpof=true&sd=true
