Question

A tree grows and increases its mass. Explain why this is not a violation of the law of conservation of matter.

Short answer

The tree's mass increases by converting carbon dioxide and water into biomass, respecting the conservation of matter.

Step-by-step solution

Understanding the Law of Conservation of Matter

The Law of Conservation of Matter states that matter cannot be created or destroyed in an isolated system. It means the amount of matter remains constant, and chemical reactions or physical changes may only change the form of matter, not its amount.

Identifying the Source of Tree Mass Increase

When a tree grows, its increase in mass primarily comes from the carbon it absorbs from carbon dioxide in the air during the process of photosynthesis. This carbon is converted into organic matter, such as cellulose and other biomolecules, which contribute to the tree's mass.

Role of Photosynthesis in Mass Increase

During photosynthesis, trees take in carbon dioxide (CO2) and water (H2O), using sunlight as energy. The chemical reaction converts these substances into glucose (C6H12O6) and oxygen (O2). The equation is: \[ 6CO_2 + 6H_2O + light ightarrow C_6H_{12}O_6 + 6O_2 \]This glucose provides the carbon necessary for biomass increase.

Examining Matter Transformation

The carbon dioxide and water are transformed into different molecules, but the total mass of the substances before and after the reaction is conserved. This means the increase in the tree’s mass is merely a transformation of atmospheric gases and water into solid form inside the tree.

Conclusion on Matter Conservation

Thus, the growth of a tree doesn't violate the law of conservation of matter because the tree is not creating matter; it is merely rearranging molecules from air and water to form its structure.

Key concepts

Photosynthesis

Photosynthesis is a vital process that allows plants, such as trees, to grow and increase in mass. It essentially powers the Earth's ecosystem by converting light energy into chemical energy. During photosynthesis, plants take in carbon dioxide (CO_2) from the air and water (H_2O) from the soil. Using sunlight as an energy source, they transform these components into glucose (C_6H_{12}O_6) and oxygen (O_2).
The overall chemical equation for photosynthesis is: \[ 6CO_2 + 6H_2O + ext{light} \rightarrow C_6H_{12}O_6 + 6O_2 \] This formula illustrates the conversion of molecules where six carbon dioxide and six water molecules yield one glucose molecule and six oxygen molecules.
Photosynthesis not only allows the tree to build strong tissues but also produces the oxygen we breathe. This beautiful natural process exemplifies the law of conservation of matter, as it alters molecules without creating or destroying any atoms.

Biomass

Biomass refers to the organic material that makes up living organisms. In the context of trees, biomass is the accumulated mass derived primarily from carbon compounds formed during photosynthesis. When a tree absorbs carbon dioxide from the atmosphere, it utilizes the carbon to build glucose and other organic molecules like cellulose, which gives trees their solid form.
The continual conversion of atmospheric carbon into tree biomass is integral to the growth and expansion of trees. It enables them to increase in size, height, and thickness. This accumulation happens while honoring the law of conservation of matter—only transforming available elements into a different form without the addition of new matter.
Creating biomass involves converting simple inorganic molecules from the environment into complex organic structures within the tree. This transformation is what results in the visibly increased size and mass of the tree.

Chemical Reactions

Chemical reactions are the processes by which matter is transformed, and photosynthesis is a prime example. Each reaction involves breaking bonds in reactant molecules and forming new bonds to create product molecules. In trees, these reactions occur using enzymes that facilitate the conversion of carbon dioxide and water into glucose and oxygen.
The law of conservation of matter is always at play in these reactions. It ensures that the mass of the products equals the mass of the reactants—a principle firmly demonstrated in the photosynthetic equation:
\[ 6CO_2 + 6H_2O + ext{light} \rightarrow C_6H_{12}O_6 + 6O_2 \]
This reaction highlights how molecules are rearranged to form new products, without any loss or gain in the overall mass. Through these chemical processes, a tree can efficiently use its surroundings to foster growth, converting what it absorbs into physical mass.