# Carbon and its Compounds - Grade 10 (SEE) Science
## Complete Chapter Notes with All Exercises - NEB Curriculum
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## 🎯 Chapter Overview
**These notes for the Class 10 Science chapter "Carbon and its Compounds" are crafted by curriculum experts to provide a detailed, step-by-step explanation of all concepts.** Aligned perfectly with the latest NEB curriculum of Nepal, these notes are designed to be a one-stop solution for students.
**This chapter is fundamental to understanding organic chemistry and is crucial for the SEE examination.** The notes cover everything from the unique properties of carbon, its various forms (allotropes), the vast world of hydrocarbons, to the laboratory preparation and properties of important carbon compounds like carbon dioxide. **All textbook exercises, including definitions, give reasons, differentiations, structural questions, and chemical reactions, are solved with clear explanations.**
**Weightage:** 10-14 marks in SEE examination
**Time Required:** 20-25 periods
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## 📚 Learning Objectives
After studying this chapter, students will be able to:
- Explain the unique properties of carbon (tetravalency and catenation).
- Differentiate between the allotropes of carbon: diamond, graphite, and fullerene.
- Define and classify hydrocarbons (saturated and unsaturated).
- Understand homologous series and functional groups.
- Write the IUPAC names of simple organic compounds.
- Define and draw structures for isomers.
- Describe the lab preparation, properties, and uses of carbon dioxide ($CO_2$).
- Explain the properties and effects of other carbon compounds like carbon monoxide (CO) and methane ($CH_4$).
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## 🔬 1. INTRODUCTION TO CARBON
### 1.1 Carbon: The Element of Life
Carbon is a non-metal element with the symbol **'C'**. It is the fourth most abundant element in the universe.
- **Atomic Number:** 6
- **Atomic Mass:** 12
- **Electronic Configuration:** 1s² 2s² 2p² or (2, 4)
- **Position in Periodic Table:** Group 14 (IVA), Period 2

### 1.2 Unique Properties of Carbon
Carbon forms millions of compounds due to its unique properties:
1.  **Tetravalency:** Carbon has **4 electrons** in its outermost shell. To achieve a stable octet configuration, it shares these 4 electrons with other atoms, forming **four covalent bonds**. This property is known as tetravalency.
2.  **Catenation:** Carbon has the unique ability to form strong covalent bonds with other carbon atoms, creating **long chains, branched chains, and rings**. This self-linking property is called catenation.



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## 💎 2. ALLOTROPES OF CARBON
**Allotropy** is the property of some chemical elements to exist in two or more different forms in the same physical state. These forms are called **allotropes**. Carbon's main crystalline allotropes are Diamond, Graphite, and Fullerene.

### 2.1 Comparison of Diamond and Graphite

| Property | Diamond | Graphite |
|---|---|---|
| **Structure** | Tetrahedral crystal lattice. Each carbon is bonded to 4 others. | Hexagonal layered structure. Each carbon is bonded to 3 others. |
| **Appearance** | Transparent, brilliant | Greyish-black, shiny |
| **Hardness** | Hardest natural substance known | Soft and slippery |
| **Electrical Conductivity**| Bad conductor (no free electrons)| Good conductor (has free electrons)|
| **Density** | High density (about 3.51 g/cm³)| Lower density (about 2.26 g/cm³)|
| **Uses** | Jewellery, cutting tools, drill bits| Pencils, lubricant, electrodes |



### 2.2 Fullerene
- Fullerenes are cage-like, spherical molecules of carbon.
- The most famous one is **Buckminsterfullerene ($C_{60}$)**, which has a shape like a soccer ball (20 hexagons and 12 pentagons).
- They are used in nanotechnology, as lubricants, and in medical research.

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## 🧪 3. ORGANIC COMPOUNDS & HYDROCARBONS
### 3.1 Organic Compounds
**Organic compounds** are the compounds of carbon, typically bonded with hydrogen, oxygen, nitrogen, and other elements. Initially, it was believed they could only be made by living organisms (Vital Force Theory), but **Friedrich Wohler** disproved this in 1828 by synthesizing **urea** (an organic compound) from an inorganic compound (ammonium cyanate).

### 3.2 Hydrocarbons
**Hydrocarbons are organic compounds containing only carbon and hydrogen atoms.** They are the simplest organic compounds.

#### A. Saturated Hydrocarbons (Alkanes)
- Hydrocarbons in which carbon atoms are linked by **single covalent bonds** only.
- **General Formula:** $C_n H_{2n+2}$ (where n = 1, 2, 3...)
- They are also called **paraffins** because they are less reactive.
- **Examples:** Methane ($CH_4$), Ethane ($C_2 H_6$), Propane ($C_3 H_8$).

#### B. Unsaturated Hydrocarbons
- Hydrocarbons in which carbon atoms are linked by at least one **double or triple covalent bond**.
- They are more reactive than alkanes.
- **Types:**
    1.  **Alkenes:** Contain at least one carbon-carbon **double bond** (C=C).
        - **General Formula:** $C_n H_{2n}$ (where n = 2, 3, 4...)
        - **Examples:** Ethene ($C_2 H_4$), Propene ($C_3 H_6$).
    2.  **Alkynes:** Contain at least one carbon-carbon **triple bond** (C≡C).
        - **General Formula:** $C_n H_{2n-2}$ (where n = 2, 3, 4...)
        - **Examples:** Ethyne ($C_2 H_2$), Propyne ($C_3 H_4$).

### 3.3 Homologous Series
A **homologous series** is a series of organic compounds with the same functional group and similar chemical properties, in which successive members differ by a $CH_2$ group.
**Characteristics:**
- All members can be represented by a general formula.
- Each successive member differs by a $CH_2$ group.
- They have similar chemical properties.
- They show a gradual change in physical properties (like boiling point) as the molecular mass increases.

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## 🏷️ 4. FUNCTIONAL GROUPS AND IUPAC NOMENCLATURE
### 4.1 Functional Group
A **functional group** is an atom or a group of atoms that determines the chemical properties of an organic compound.
| Functional Group | Formula | IUPAC Suffix | Example |
|---|---|---|---|
| Alcohol | -OH | -ol | Methanol ($CH_3OH$) |
| Aldehyde | -CHO | -al | Ethanal ($CH_3CHO$) |
| Ketone | >C=O | -one | Propanone ($CH_3COCH_3$) |
| Carboxylic Acid | -COOH| -oic acid| Ethanoic acid ($CH_3COOH$)|
| Halo | -X (F, Cl, Br, I)| (Prefix) Halo- | Chloroethane ($C_2H_5Cl$) |

### 4.2 Isomerism
**Isomers** are compounds that have the **same molecular formula but different structural formulas** (different arrangements of atoms). This phenomenon is known as isomerism.
**Example: Isomers of Butane ($C_4 H_{10}$)**
1.  **n-butane:** A straight chain.
    $CH_3 - CH_2 - CH_2 - CH_3$
2.  **iso-butane (2-methylpropane):** A branched chain.
    $CH_3 - CH(CH_3) - CH_3$

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## 💨 5. IMPORTANT CARBON COMPOUNDS
### 5.1 Carbon Dioxide ($CO_2$)
#### A. Laboratory Preparation
Carbon dioxide is prepared in the lab by the reaction of calcium carbonate (marble chips or limestone) with dilute hydrochloric acid.


[Image of the laboratory preparation of carbon dioxide gas]


- **Principle Reaction:**
  $CaCO_3(s) + 2HCl(dil) \rightarrow CaCl_2(aq) + H_2O(l) + CO_2(g) \uparrow$
- **Procedure:** Marble chips are placed in a Woulfe's bottle, and dilute HCl is added through a thistle funnel. The gas produced is collected in an upward gas jar by the **upward displacement of air** because it is heavier than air.
- **Gas Test:** When a burning matchstick is brought near the gas jar, it extinguishes. When the gas is passed through lime water ($Ca(OH)_2$), the lime water turns milky due to the formation of a white precipitate of calcium carbonate ($CaCO_3$).
  $Ca(OH)_2(aq) + CO_2(g) \rightarrow CaCO_3(s) \downarrow + H_2O(l)$

#### B. Properties and Uses
- **Physical Properties:** Colorless, odorless gas, heavier than air, slightly soluble in water.
- **Chemical Properties:**
    - Neither combustible nor a supporter of combustion.
    - Acidic in nature (turns moist blue litmus paper red).
    - Reacts with burning magnesium: $2Mg + CO_2 \rightarrow 2MgO + C$
- **Uses:**
    - In fire extinguishers.
    - In soft drinks (to make them fizzy).
    - As dry ice (solid $CO_2$) for refrigeration.
    - In photosynthesis by plants.

### 5.2 Other Important Compounds
- **Carbon Monoxide (CO):** A colorless, odorless, and highly poisonous gas formed by the incomplete combustion of carbon fuels. It is dangerous because it binds to hemoglobin in the blood more strongly than oxygen, leading to oxygen deprivation.
- **Methane ($CH_4$):** The simplest alkane. It is the main component of natural gas and biogas. It is used as a fuel.

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## 📋 6. COMPLETE EXERCISE SOLUTIONS
### **1. Define the following:**
**a. Catenation:** The self-linking property of carbon atoms to form long chains, branched chains, and rings through covalent bonds is called catenation.
**b. Tetravalency:** The property of a carbon atom to form four covalent bonds by sharing its four valence electrons is called tetravalency.
**c. Allotropy:** The phenomenon in which an element exists in two or more different forms in the same physical state is called allotropy.
**d. Hydrocarbons:** Organic compounds containing only carbon and hydrogen are called hydrocarbons.
**e. Homologous Series:** A series of organic compounds having the same functional group and similar chemical properties, where successive members differ by a $CH_2$ group.
**f. Isomerism:** The phenomenon in which compounds have the same molecular formula but different structural formulas is called isomerism.

### **2. Answer the following questions:**
**a. Why does carbon form a very large number of compounds?**
**Answer:** Carbon forms a very large number of compounds mainly due to two unique properties:
1.  **Tetravalency:** It can form four covalent bonds with other atoms.
2.  **Catenation:** It can link with other carbon atoms to form long chains and rings.

**b. Write the general formula of alkanes, alkenes, and alkynes.**
**Answer:**
- **Alkane:** $C_n H_{2n+2}$
- **Alkene:** $C_n H_{2n}$
- **Alkyne:** $C_n H_{2n-2}$

**c. Draw the isomers of pentane ($C_5 H_{12}$) and write their IUPAC names.**
**Answer:** Pentane has three structural isomers:
1.  **n-pentane:** $CH_3 - CH_2 - CH_2 - CH_2 - CH_3$
2.  **Isopentane (2-methylbutane):** $CH_3 - CH(CH_3) - CH_2 - CH_3$
3.  **Neopentane (2,2-dimethylpropane):** $C(CH_3)_4$

**d. Describe the laboratory preparation of carbon dioxide gas with a labeled diagram and a balanced chemical equation.**
**Answer:** Carbon dioxide is prepared in the lab by reacting calcium carbonate with dilute hydrochloric acid.
**Principle:** $CaCO_3 + 2HCl \rightarrow CaCl_2 + H_2O + CO_2$
**Procedure:** (As described in section 5.1 A)
**(A neat, labeled diagram showing a Woulfe's bottle, thistle funnel, delivery tube, and an upward gas jar must be drawn).**

**e. What happens when carbon dioxide is passed through lime water for a short time and then for a long time? Write balanced equations.**
**Answer:**
- **Short time:** Lime water turns milky due to the formation of insoluble calcium carbonate.
  $Ca(OH)_2 + CO_2 \rightarrow CaCO_3 \downarrow + H_2O$
- **Long time:** The milkiness disappears due to the formation of soluble calcium bicarbonate.
  $CaCO_3 + H_2O + CO_2 \rightarrow Ca(HCO_3)_2$ (soluble)

### **3. Distinguish between:**
**a. Saturated and Unsaturated Hydrocarbons**
| Saturated Hydrocarbons | Unsaturated Hydrocarbons |
|---|---|
| Contain only C-C single bonds. | Contain at least one C=C or C≡C bond. |
| General formula is $C_n H_{2n+2}$ (Alkanes).| General formula is $C_n H_{2n}$ (Alkenes) or $C_n H_{2n-2}$ (Alkynes).|
| They are less reactive. | They are more reactive. |
| Example: Ethane ($C_2 H_6$) | Example: Ethene ($C_2 H_4$), Ethyne ($C_2 H_2$) |

**b. Diamond and Graphite**
| Diamond | Graphite |
|---|---|
| It is the hardest natural substance.| It is soft and slippery. |
| It is a bad conductor of electricity. | It is a good conductor of electricity. |
| Each carbon atom is bonded to 4 others.| Each carbon atom is bonded to 3 others.|
| It has a tetrahedral structure. | It has a hexagonal layered structure. |

### **4. Give reasons:**
**a. Diamond is very hard while graphite is soft.**
**Answer:** In diamond, each carbon atom is strongly bonded to four other carbon atoms in a rigid, three-dimensional tetrahedral network. In graphite, carbon atoms are arranged in hexagonal layers that can slide over one another, making it soft.

**b. Graphite is a good conductor of electricity but diamond is not.**
**Answer:** In graphite, each carbon atom is bonded to only three other carbon atoms, leaving one free electron per atom. These free electrons are mobile and can conduct electricity. In diamond, all four valence electrons of each carbon atom are used in bonding, so there are no free electrons to conduct electricity.

**c. Carbon monoxide is considered a poisonous gas.**
**Answer:** Carbon monoxide is poisonous because when inhaled, it binds very strongly with the hemoglobin in red blood cells, forming carboxyhemoglobin. This reduces the oxygen-carrying capacity of the blood, leading to oxygen starvation, suffocation, and death.

**d. Carbon dioxide gas is collected by the upward displacement of air.**
**Answer:** Carbon dioxide gas is about 1.5 times heavier than air. Therefore, when collected in a gas jar, it settles at the bottom and displaces the lighter air upwards.

**e. An iron nail sinks in water but a huge ship made of iron floats.**
**Answer:** This question relates more to the chapter on Pressure/Archimedes' Principle. The reason is density. An iron nail is solid, and its density is much greater than water, so it sinks. An iron ship is hollow and contains a lot of air. Its overall average density (mass of the ship divided by its total volume) is less than the density of water, so it floats.

### **5. Structural and IUPAC Naming Questions:**
**a. Write the structural formula and IUPAC name of the 2nd member of the alkene series.**
- **Molecular Formula:** For alkene, $C_n H_{2n}$. For 2nd member, n=3. So, $C_3 H_6$.
- **IUPAC Name:** Propene
- **Structure:** $CH_2 = CH - CH_3$

**b. Identify the functional group in $CH_3COOH$ and write its IUPAC name.**
- **Functional Group:** Carboxylic acid (-COOH)
- **IUPAC Name:** Ethanoic acid

**c. Draw the electron-dot structure of methane ($CH_4$).**
**Answer:** In the electron-dot structure, the central carbon atom shares one electron with each of the four hydrogen atoms. Each hydrogen atom shares its one electron with carbon. This results in carbon having a stable octet and each hydrogen having a stable duplet.
**(Draw a central 'C' with 4 dots around it. Draw four 'H' atoms around the 'C', each with one 'x'. Circle one dot and one 'x' for each C-H bond.)**

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## 📈 7. IMPORTANT FORMULAS & REACTIONS SUMMARY
### **Hydrocarbon Formulas**
- **Alkane:** $C_n H_{2n+2}$
- **Alkene:** $C_n H_{2n}$
- **Alkyne:** $C_n H_{2n-2}$

### **Key Reactions**
- **$CO_2$ Lab Preparation:** $CaCO_3 + 2HCl \rightarrow CaCl_2 + H_2O + CO_2$
- **Lime Water Test:** $Ca(OH)_2 + CO_2 \rightarrow CaCO_3 \downarrow + H_2O$
- **Incomplete Combustion:** $2C + O_2 \rightarrow 2CO$
- **Complete Combustion:** $C + O_2 \rightarrow CO_2$

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## 🏆 8. EXAM PREPARATION TIPS
- **High Priority Topics:** Allotropes of carbon (especially the differences between diamond and graphite), Hydrocarbons (saturated vs. unsaturated), and the Lab Preparation of $CO_2$.
- **Practice Drawing:** Be perfect in drawing the lab preparation setup for $CO_2$, the structures of diamond and graphite, and the isomers of butane and pentane.
- **Master IUPAC:** Learn the basic rules for naming simple alkanes, alkenes, alkynes, and compounds with -OH and -COOH groups.
- **Give Reasons:** Understand the 'why' behind concepts. Questions like "Why is diamond hard?" are very common.
- **Balanced Equations:** Memorize and practice writing the balanced chemical equations for the preparation and tests of $CO_2$.

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## ✅ 9. CHAPTER CHECKLIST
**Before your SEE Exam, make sure you can:**
- [ ] Define catenation and tetravalency.
- [ ] List at least three differences between diamond and graphite.
- [ ] Classify hydrocarbons into alkanes, alkenes, and alkynes with their general formulas.
- [ ] Draw the labeled diagram for the lab preparation of $CO_2$.
- [ ] Write all chemical equations related to $CO_2$.
- [ ] Draw the isomers of butane ($C_4 H_{10}$).
- [ ] Explain why carbon monoxide is poisonous.
- [ ] Give the IUPAC name for simple organic compounds.

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## 🎊 CONCLUSION
The chapter "Carbon and its Compounds" opens the door to the vast and fascinating world of organic chemistry. Its concepts are not just essential for your SEE exams but also form the foundation for higher studies in science. **These comprehensive notes, with complete exercise solutions, are designed to make your learning process smooth, clear, and effective.** By mastering the unique properties of carbon, you'll understand why it is the backbone of life itself.
**Key to Success:** Understand the Concepts + Practice Drawing Structures + Memorize Key Reactions = Excellent Marks!
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