Carbon is a non-metal existing in various allotropes, each with unique properties. Diamond, the hardest known natural substance, boasts exceptionally high melting and boiling points, while graphite, another allotrope, conducts electricity. These differing properties stem from the distinct arrangement of carbon atoms in their respective structures. Carbon's versatility makes it a crucial element, forming the basis of organic chemistry and essential to life itself. Its ability to bond in diverse ways contributes to the vast array of organic compounds found in nature and synthesized by humans.

The types of chemical reactions are combination, decomposition, displacement, double displacement, and redox (oxidation-reduction).

The Indian economy, like most others, is divided into three main sectors: * **Primary Sector:** This sector involves the extraction and production of raw materials. Examples include agriculture (farming, forestry), fishing, and mining. * **Secondary Sector:** This sector focuses on manufacturing and processing of raw materials into finished goods. Examples include industries, construction, and power generation. * **Tertiary Sector (Services Sector):** This sector provides services to individuals and businesses. Examples include banking, finance, insurance, transportation, communication, healthcare, education, and tourism.

1. **Carbon's Allotropy:** * *Exists in different forms (allotropes).* 2. **Diamond (allotrope):** * *Hardest natural substance.* * *High melting/boiling point.* 3. **Graphite (allotrope):** * *Conducts electricity.*

1. **Heredity Definition:** *The passing of traits from parents to offspring during reproduction.* 2. **Key Aspects:** *Offspring resemble parents. *Variations exist due to DNA copying differences. *These variations drive evolution and adaptation.

Acids are one of the three main categories of chemical compounds (along with bases and salts). They are characterized by several key properties: * **Taste:** Acids have a sour taste. Think of the sourness of lemon juice (citric acid) or vinegar (acetic acid). * **Effect on litmus:** Acids turn blue litmus paper red. Litmus paper is an indicator – a substance that changes color depending on whether a solution is acidic or basic. * **Reactions with metals:** Acids react with many metals, producing hydrogen gas (H₂) as a byproduct. This is a characteristic chemical reaction of acids. * **Reactions with carbonates:** Acids react with carbonates (like calcium carbonate in limestone) to produce carbon dioxide (CO₂) gas, water, and a salt. * **pH scale:** Acids have a pH less than 7 on the pH scale, which measures acidity and basicity. The lower the pH, the stronger the acid. * **Neutralization:** Acids react with bases in a neutralization reaction to form salt and water. Acids are classified as strong or weak based on their degree of ionization (how readily they release hydrogen ions, H⁺, in solution). Strong acids ionize completely, while weak acids only partially ionize. Acids are found in many everyday applications and are vital in various biological processes. Examples include citric acid in fruits, acetic acid in vinegar, and hydrochloric acid in our stomachs (which aids digestion).

The provided text describes several chemical reactions, but doesn't explicitly define what a chemical reaction *is*. It shows examples like: * **Acids reacting with metals:** Producing hydrogen gas. * **Acids reacting with carbonates:** Producing carbon dioxide gas. * **Neutralization reactions:** Acids and bases reacting to form salt and water. A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. This transformation involves the rearrangement of atoms and/or molecules, creating new substances with different properties. The text illustrates this with the formation of new substances (hydrogen gas, carbon dioxide, salt and water) from the reactants.

Carbon exists in allotropes like diamond and graphite, varying in properties.

* **Essential functions for life maintenance.** * **Includes:** nutrition, respiration, transport, excretion. * **Requires constant molecular movement within cells.** * **Continues even during rest (e.g., breathing, tissue repair).** * **Energy from food is crucial.** * **Depends on continuous energy input and system maintenance.**