Short Questions and Answers from the Class 8 CBSE Science Book

Question 1: What is the mode of nutrition in plants?

Answer:
Plants have the ability to synthesize their own food by the process of photosynthesis. This means that the mode of nutrition in plants is autotrophic. Autotrophic nutrition refers to the ability of an organism to produce its own food using simple inorganic substances like carbon dioxide and water, with the help of sunlight and chlorophyll.

Question 2: What is combustion?

Answer:
Combustion is a chemical process in which a substance reacts rapidly with oxygen and releases energy in the form of heat and light. It is an exothermic reaction that occurs when a fuel (such as wood, coal, or gasoline) combines with oxygen in the presence of a source of ignition (such as a spark or flame). The reactants of combustion are the fuel and oxygen, while the products are carbon dioxide, water, and heat.

Question 3: What is the function of a cell membrane?

Answer:
The cell membrane, also known as the plasma membrane, is a thin, flexible barrier that surrounds the cell and separates the internal environment of the cell from its external surroundings. The main function of the cell membrane is to regulate the movement of substances in and out of the cell. It is selectively permeable, which means it allows certain substances to enter or leave the cell while restricting the passage of others.

The key functions of the cell membrane include:
- Protection: It provides a protective barrier for the cell, preventing the entry of harmful substances and maintaining the integrity of the cell.
- Transport: It regulates the movement of ions, molecules, and nutrients into and out of the cell through various transport mechanisms such as diffusion, osmosis, and active transport.
- Cell recognition: The cell membrane contains receptors and markers that help in cell recognition and communication with other cells.
- Cell signaling: It plays a crucial role in cell signaling by transmitting signals from the external environment to the cell's interior, allowing the cell to respond to changes in its surroundings.
- Structural support: The cell membrane helps maintain the shape and structure of the cell by providing mechanical support.

Overall, the cell membrane is essential for the survival and functioning of the cell by controlling its interactions with the external environment.

Question 4: What is a mixture?

Answer:
A mixture is a combination of two or more substances that are not chemically combined. In a mixture, the individual substances retain their own physical properties and can be separated by physical means. Mixtures can be classified into two types: homogeneous and heterogeneous.

- Homogeneous mixture: A homogeneous mixture is uniform in composition, meaning that the components are evenly distributed throughout the mixture. Examples of homogeneous mixtures include saltwater, air, and sugar dissolved in water.

- Heterogeneous mixture: A heterogeneous mixture has non-uniform composition, with visible differences in the distribution of its components. Examples of heterogeneous mixtures include a mixture of sand and water,

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