Conservation of mass
No The smallest part of an element that can exist. are created or destroyed in a chemical reaction. Instead, they just join together in a different way than they were before the reaction, and form A substance formed in a chemical reaction.. This means that the total The amount of matter an object contains. Mass is measured in kilograms (kg) or grams (g). of the products in a chemical reaction will be the same as the total mass of the A substance that reacts together with another substance to form products during a chemical reaction..
The total mass stays the same during a chemical reaction. This is the law of conservation of mass.
Calculations using the law
The mass of one substance in a reaction can be calculated if the masses of the other substances are known. For example:
Image caption, Calcium carbonate is made up of 28 grams of calcium oxide and 22 grams of carbon dioxide
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Reactions in closed systems
No substances can enter or leave a A reaction vessel where no reactants or products can escape or are lost to the surroundings.. A simple closed system could be a sealed container such as a stoppered flask.
The reactants and products stay in the beaker. The total mass of the beaker and the substances it contains stays the same during the reaction.
Reactions in non-enclosed systems
Substances can enter or leave a In chemistry, a system in which gases or other substances can enter or leave during a reaction.. These systems are often open flasks or crucibles that let gases enter or leave. If a gas escapes, the total mass will look as if it has decreased. If a gas is gained, the total mass will look as if it has increased. However, the total mass stays the same if the mass of the gas is included.
Example
Zinc reacts with hydrochloric acid to produce zinc chloride and hydrogen gas.
Zn(s) + 2HCl(aq) \(\rightarrow\) ZnCl2(aq)+ H2(g)
Use the The scientific theory used to explain the properties of solids, liquids and gases. It involves the arrangement and movement of the particles in a substance. to explain why the reaction between zinc and hydrochloric acid appears to lose mass.
During a reaction no atoms can be created or destroyed. The hydrogen atoms from the hydrochloric acid in solution become hydrogen gas A collection of two or more atoms held together by chemical bonds. in the products. The reaction takes place in an open container. According to the particle model, particles in a gas are free to move position and are far apart. The hydrogen gas can therefore escape into the atmosphere. This causes the mass measured to decrease.