use atomic theory to explain why chemical reactions obey the law of conservation of mass
matter in the reactants just rearrange themselves into products, it is the same total matter.
Chemical reactions obey the law of conservation of mass because the total # of atoms of an element in a chemical reaction stays the same, which means that the atoms can't be created or destroyed because the total # of atoms always stays the same. It's Dalton's atomic theory!
Atomic theory provides a framework for understanding why chemical reactions obey the law of conservation of mass. According to atomic theory:
1. All matter is composed of tiny, indivisible particles called atoms.
2. Atoms of different elements have distinct properties.
3. Chemical reactions involve the rearrangement of atoms to form new substances.
The law of conservation of mass states that matter cannot be created or destroyed during a chemical reaction, only rearranged. This principle aligns with atomic theory in the following ways:
1. Atoms are neither created nor destroyed in a chemical reaction:
- In a reaction, the atoms in the reactants rearrange to form new compounds.
- The total number of atoms of each element involved in a reaction remains constant.
2. Atoms are indivisible:
- Atoms cannot be split or destroyed into smaller, subatomic particles during a chemical reaction.
- Instead, they rearrange to form new compounds, maintaining their identity and properties.
3. Atoms have a specific mass:
- Each atom has a unique mass that is measured relative to the carbon-12 isotope (atomic mass unit).
- During a chemical reaction, the total mass of the reactants is equal to the total mass of the products, as no atoms are lost or gained.
Thus, the law of conservation of mass aligns with atomic theory because it implies that the total number of atoms and their mass remain constant in a chemical reaction, reinforcing the idea that atoms are indivisible and cannot be created or destroyed.
To explain why chemical reactions obey the law of conservation of mass using atomic theory, we need to understand a few key concepts.
Atomic theory, proposed by John Dalton in the early 19th century, states that matter is composed of tiny indivisible particles called atoms. According to this theory, atoms combine and rearrange in chemical reactions, but they are neither created nor destroyed.
Now, let's consider a typical chemical reaction as an example. Let's say we have a reaction where hydrogen gas (H2) reacts with oxygen gas (O2) to produce water (H2O).
1. Balanced Equation: We start by writing the balanced chemical equation for the reaction:
2H2 + O2 -> 2H2O
2. Molar Ratios: The coefficients in the balanced equation represent the molar ratios of the reactants and products. In this case, 2 moles of hydrogen gas react with 1 mole of oxygen gas to produce 2 moles of water.
3. Mass Conservation: According to the law of conservation of mass, mass is neither created nor destroyed in a chemical reaction. This means that the total mass of the reactants must be equal to the total mass of the products.
In the example reaction above, the total mass of the reactants (hydrogen gas and oxygen gas) is equal to the total mass of the products (water):
Reactants:
2H2 (2 moles) = 2 x 2.02 g/mol = 4.04 g
O2 (1 mole) = 1 x 32.00 g/mol = 32.00 g
Total mass of reactants = 4.04 g + 32.00 g = 36.04 g
Products:
2H2O (2 moles) = 2 x 18.02 g/mol = 36.04 g
Total mass of products = 36.04 g
As you can see, the total mass of the reactants (36.04 g) is equal to the total mass of the products (36.04 g). This demonstrates the principle of mass conservation in a chemical reaction.
According to atomic theory, atoms are neither created nor destroyed in chemical reactions. Instead, they rearrange to form different molecules. In our example, the hydrogen atoms from hydrogen gas combine with the oxygen atoms from oxygen gas to form water molecules. The original atoms are not lost or gained; they are simply reshuffled to create different substances.
This adherence to the law of conservation of mass provides evidence for the validity of atomic theory in explaining chemical reactions.