Conservation Laws
Conservation Laws - Related Videos
09:46
Conservation of Momentum
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2023
Source: Nicholas Timmons, Asantha Cooray, PhD, Department of Physics & Astronomy, School of Physical Sciences, University of California, Irvine, CA The goal of this experiment is to test the concept of the conservation of momentum. By setting up a surface with very little friction, collisions between moving objects can be studied, including their initial and final momenta. The conservation of momentum is one of the most important laws in physics. When something is conserved in physics, the...
02:31
Scientific Laws and Theories
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2020
Scientific Laws In science, a law is defined as a concise, verbal or mathematical, statement that summarizes a vast number of experimental observations. It describes or predicts some facets of the natural world that always remain the same under the same conditions. Scientific Theory A scientific theory is a unifying principle that provides a well-substantiated and testable explanation of aspects of nature and provides the reason for why things happen. Well-established theories are the...
02:16
First Law of Thermodynamics
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2020
Energy Conservation Energy can be converted from one form into another, but all of the energy present before a change occurs always exists in some form after the change is completed. This observation is expressed in the law of conservation of energy: during a chemical or physical change, energy can be neither created nor destroyed, although it can be changed in form. According to the law of conservation of matter, there is no detectable change in the total amount of matter during a chemical...
02:49
Second Law of Thermodynamics
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2020
In the quest to identify a property that may reliably predict the spontaneity of a process, a promising candidate has been identified: entropy. Processes that involve an increase in entropy of the system (ΔS > 0) are very often spontaneous; however, examples to the contrary are plentiful. By expanding consideration of entropy changes to include the surroundings, a significant conclusion regarding the relation between this property and spontaneity may be reached. In thermodynamic models, the...
04:06
Ideal Gas Law - Concepts
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2020
Derivation of the Ideal Gas Law Gases are a fundamental state of matter. A gas is a collection of molecules that have a significant distance between their molecules. Due to this distance, colorless gases are invisible to the human eye and are studied using four measurable parameters: pressure (P), volume (V), number of moles (n), and temperature (T). The ideal gas law is a mathematical equation that relates all of these parameters. It is a combination of several different laws that describe the...
FAQs
Chemical equations track atoms by element because reactions rearrange existing atoms into new combinations. A coefficient changes the number of whole molecules or formula units, whereas a subscript changes a substance’s composition and therefore cannot be altered during balancing. Matching each element on both sides preserves the molecular accounting needed for valid stoichiometric calculations.
Charge provides a second accounting requirement, especially for reactions involving ions or electrons. The total positive and negative charge must match on the reactant and product sides, even when atoms are redistributed. Checking charge alongside elemental composition helps identify missing ionic species or electrons and is essential when representing electron-transfer processes accurately.
Conservation of mass tracks the amounts of elements through a transformation, while conservation of energy tracks energy transfers or changes associated with that transformation. A balanced equation can satisfy elemental accounting without indicating how energy is distributed. Considering both principles gives a fuller analysis of chemical systems, including reaction calculations and their thermodynamic context.
A proposed transformation satisfies the relevant conservation constraints when its products contain the same elemental inventory and total charge as its reactants, with energy accounted for in the broader system description. If an equation fails these checks, it cannot represent the stated chemical process as written. Conservation therefore provides an early test of chemical plausibility.
First write the correct formulas for all reactants and products, then compare the number of atoms of each element on both sides. Adjust coefficients, not subscripts, until every elemental count agrees; for ionic reactions, check total charge as well. The resulting coefficients establish the mole relationships used in subsequent stoichiometric calculations.
Balanced-equation coefficients provide quantitative ratios between reactants and products. These ratios allow a known amount of one substance to be converted into the corresponding amounts of other substances, provided the chemical formulas and units are handled consistently. Conservation makes those ratios meaningful because they represent the same elemental inventory before and after the reaction.
Comparing measured or predicted products with conserved elemental amounts and charge can reveal an incomplete equation, an omitted product, or an accounting error. Conservation does not by itself determine every reaction outcome, but it restricts which outcomes are possible. Combined with energy considerations, it helps researchers assess whether a proposed transformation is chemically consistent.
At the molecular level, reactions rearrange atoms and redistribute electrons; at the system level, conservation principles organize the resulting changes in matter and energy. This connection lets chemists relate a symbolic equation to measurable reaction behavior and thermodynamic models. The same accounting framework supports reaction analysis while distinguishing composition changes from energy changes.