Conservation of Mass (GCSE Chemistry)
Conservation of Mass
Conservation of Mass
Mass is always conserved during a chemical reaction. When a chemical reaction takes place, the relative formula mass of the reactants is always equal to the relative formula mass of the products.
The law of conservation of mass applies to chemical reactions. All chemical reactions follow the ‘law of conservation of mass’. This law states that:
“No atoms are destroyed or created during a chemical reaction.”
The same number and types of atoms are on both sides of the equation. In any reaction, we should have the same types and the same numbers of atoms on both sides of the equation. Again, this follows the law of conservation of mass.
H2 + O → H2O
Calculations for Change in Mass in Reactants
You need to be able to work out the change in mass in a reaction using a balanced symbol equation. This can be helpful when explaining the reason for mass changes and understanding how the mass changes occurs.
2 Mg + O2 → 2 MgO
Practice Question:
Using the balanced equation, show whether mass is conserved in the following reaction: Mg (s) + 2H2O (l) -> Mg(OH)2 (aq) + H2 (g)
1.Add up the relative formula masses of reactants. To do this, we can use a periodic table.
Mr(Mg) = 24
Mr(H2O) = 2 x ((2 x 1) + 16) = 36
Overall Mr of reactants = 24 + 36 = 60
2. Add up the relative formula masses of the products. Again, we need our periodic table for this step.
Mr (Mg(OH)2) = 24 + ( 2 x (16 + 1)) =58
Mr (H2) = 2 x 1 = 2
Overall Mr of products = 58 + 2 = 60
3. Check that Mr of products equals mr of reactants.
Overall Mr of reactants = 24 + 36 = 60
Overall Mr of products = 58 + 2 = 60
Mass is conserved.
Mass Changes in an Equation
In some experiments, there is a change of mass. There can be mass changes between the products and the reactants in certain types of reactions. The mass can increase or decrease.
Mass changes occur with changes of state. If reactants undergo a change of state to become the products, this means that the mass of the products will be different to the mass of the reactants.
Increases in Mass
Reactants can be atmospheric gases. Some reactants (such as carbon dioxide) can be found in air. We cannot measure the ‘mass’ of these reactants, since they are free in the air.
Products settle in the reaction vessel. If the products are solids or liquids they will settle into the reaction vessel and become contained within it. There has been a change of mass during the reaction, leading to an increase in mass of the reaction vessel overall
Decreases in Mass
Products can be atmospheric gases. Some products (such as carbon dioxide) can be released into the air. We can no longer measure the mass of these products since they are free in the air.
Reactants can change state to become gaseous products. During a reaction, liquid or solid reactants can change state and turn into a gas. Gases have a smaller mass compared to solid and liquids.
Products can escape from the reaction vessel. If the products are gases, they can’t be ‘contained’ in the reaction vessel. There has been a change of mass in the reaction, leading to a decrease in the mass of the reaction vessel overall.
The law of conservation of mass in GCSE Chemistry states that the total mass of the reactants in a chemical reaction is equal to the total mass of the products. In other words, mass cannot be created or destroyed in a chemical reaction.
The law of conservation of mass is important in GCSE Chemistry because it provides a fundamental understanding of how matter behaves in chemical reactions. It allows scientists to predict the mass of the products in a reaction and to determine the amount of reactants required to produce a specific amount of products.
The law of conservation of mass can be demonstrated in GCSE Chemistry experiments by carefully measuring the mass of the reactants and products before and after a chemical reaction takes place. If the law of conservation of mass is upheld, the total mass of the reactants and products should remain the same.
No, the law of conservation of mass cannot be violated in GCSE Chemistry. It is a fundamental principle that applies to all chemical reactions and is considered to be one of the most important laws in the field of chemistry.
The real-world applications of the law of conservation of mass in GCSE Chemistry include:
Environmental monitoring: The law of conservation of mass can be used to monitor the release and disposal of hazardous chemicals, ensuring that they do not harm the environment.
Quality control in industry: The law of conservation of mass is also used to ensure the quality and purity of products in various industries, including pharmaceuticals, food, and cosmetics.
Waste management: The law of conservation of mass is used in waste management to determine the most efficient ways to recycle materials and minimize the amount of waste that goes to landfills.
Food production: The law of conservation of mass can be used in food production to calculate the amount of feed required to produce a certain amount of meat or dairy products.
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