Question

• Classify the following change in as many ways as possible.
  Growth of a tree

Answer 1

The following changes were the observed in growth of a tree:

Slow change:

• The type of changes that occurs over a long period of time are considered slow changes.
• The tree's growth is slow because it takes days to months for a seed to grow into a sapling, then years to grow into a tree.

Natural change:

• It is the type of change that occurs in its nature without the interference of human beings.
• The growth of a tree is natural because all of the processes occur naturally and rely on natural resources such as water, sunlight, and soil.

Chemical change:

• A change in which the composition and chemical properties of the substance get changed is called a chemical change.
• During a chemical change, one or more new substances are formed.
• The growth of a tree is a chemical change because photosynthesis and respiration are chemical changes that convert light, water, and carbon dioxide into oxygen and glucose, which are then used as energy by the tree.
• We call this a chemical change because the composition of the initial substances is changed during the process.

Respiration in plants:

• In plants, respiration is done during the day and night.
• Plants - Respiration is done through tiny pores on the surface of the leaves called ‘stomata’.
• The stomata help in taking Oxygen from the air and giving out Carbon dioxide. Thus, they help in the exchange of gases.
• The balanced equation for respiration is as follows:
• $$\begin{gathered} {\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\left(\mathrm{s}\right)+6{\mathrm{O}}_2\left(\mathrm{g}\right)\to 6{\mathrm{CO}}_2\left(\mathrm{g}\right)+6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+\mathrm{Energy} \\ \mathrm{Glucose}\mathrm{Oxygen}\mathrm{Carbon}\mathrm{dioxide}\mathrm{Water} \end{gathered}$$

Photosynthesis in plants:

• Photosynthesis is a process by which green plants prepare their own food in the presence of sunlight, and Carbon dioxide. water and chlorophyll.
• In the leaf of a green plant are present leaf cells which contain chloroplasts which is present a green pigment called chlorophyll.
• The photosynthesis process occurs during the daytime, carbon dioxide and water in the presence of sunlight, carbon dioxide, water, and chlorophyll are changed into glucose, and oxygen is released.
• $$\begin{gathered} 6{\mathrm{CO}}_2\left(\mathrm{g}\right)+12{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\underset{\mathrm{chlorophyll}}{\overset{\mathrm{sunlight}}{\to }}{\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\left(\mathrm{s}\right)+6{\mathrm{O}}_2\left(\mathrm{g}\right)+6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{Carbon}\mathrm{dioxide}\mathrm{Water}\mathrm{Glucose}\mathrm{Carbon}\mathrm{dioxide}\mathrm{Water} \end{gathered}$$

Physical change:

• A change in which only the physical properties of any substance get changed is called a physical change.
• During a physical change, no new substance is formed.
• It is a physical change because the tree's growth occurs due to an increase in cell number and size.
• Growth of the tree is observed due to an increase in the size and mass of the plant. It is a very slow process and also irreversible.

Non-periodic change:

• The changes that do not occur periodically at regular intervals are known as non-periodic changes.
• The growth of a tree is considered to be non-periodic because there are no specific time intervals during which changes take place.

Irreversible change:

• The change which cannot be reversed even by changing conditions is said to be an irreversible change.
• The change that occurs during plant growth is irreversible. A tree cannot be transformed into a small plant or seed. As a result, plant growth is an irreversible change.