Carbon and its Compounds — Complete Grade 10 Chemistry Guide

Part 1: learn by doing, easy to hard · Part 2: going further, with NASA and university references · free and printable

Which syllabus are you studying?

1. The covalent bond

Salt solution conducts electricity. Why doesn't sugar solution?

Carbon has 4 outer electrons. To fill its shell to 8 it could gain 4 or lose 4. Which is easier? Write your answer, then open.

Carbon shares electrons: the shared pair counts for both atoms, so both shells fill. A bond formed this way is a covalent bond.

No ions form and intermolecular forces are weak, so covalent compounds have low melting and boiling points and are poor conductors.

Sugar is covalent: dissolving it produces no ions, so there is nothing to carry charge — no current.

Level 1 What kind of bond is in H₂, O₂ and N₂?

Level 2 Why does carbon not form ionic bonds?

Level 3 Draw the dot-and-cross diagram of ammonia, NH₃. How many of nitrogen's electrons are not shared?

2. The versatile nature of carbon

More carbon compounds are known than those of all other elements together. Why?

In the simulation below choose "Make Molecules". Drag carbon and hydrogen atoms together. How many hydrogens will attach to one carbon? Then try joining two carbons.

Simulation: PhET Interactive Simulations, University of Colorado Boulder — CC-BY 4.0.

Four hydrogens attached — and carbon bonded to carbon. Exactly the two properties:

Same formula, different structure = structural isomers (Figure 4). Rings also occur: cyclohexane C₆H₁₂, benzene C₆H₆.

Answer: catenation gives chains, branches and rings of any length; tetravalency puts four different atoms on each carbon. Multiply the two.

Level 1 Give one difference between saturated and unsaturated compounds.

Level 2 Draw propane (C₃H₈). How many covalent bonds does it contain?

Level 3 Does pentane (C₅H₁₂) have isomers? How many can you draw?

3. Homologous series and naming

Methane, ethane, propane… is there a pattern in the names? And in the formulae?

Compounds sharing a functional group whose consecutive members differ by –CH₂– (14 u) form a homologous series. Physical properties change gradually; chemical properties stay the same.

Name CH₃CH₂Br, HCHO and CH₃COCH₃.

Level 1 By what mass do consecutive members of a homologous series differ?

Level 2 Name the third member of the alkene series and give its formula.

Level 3 Of CH₃OH, C₂H₅OH and C₃H₇OH, which boils highest and why? What about their chemical behaviour?

4. Chemical properties

A gas hob leaves the pan clean — but block its air holes and the base turns black. Why?

Burn three things separately in tongs: camphor, spirit and a naphthalene ball. Predict which will smoke.

(a) Combustion

Saturated hydrocarbons burn with a clean blue flame; unsaturated ones — or any fuel short of air — burn yellow and sooty, the carbon unburnt. Coal and petroleum also contain sulfur and nitrogen, whose oxides pollute the air.

(b) Oxidation

Substances that supply oxygen to others are oxidising agents.

(c) Addition reaction

Unsaturated compounds add hydrogen and become saturated — the hydrogenation of vegetable oils. A catalyst alters a reaction rate without itself changing.

(d) Substitution reaction

In sunlight chlorine replaces the hydrogens one at a time.

Answer: blocked air holes = less air = incomplete combustion = soot on the pan. Open them and the flame turns blue again.

Level 1 Which catalyst is used to hydrogenate vegetable oils?

Level 2 Distinguish addition from substitution, with an example of each.

Level 3 A student says burning ethanol and oxidising it with KMnO₄ are both oxidation, so why teach them separately? How would you reply?

5. Ethanol, C₂H₅OH

Cough syrups and tincture of iodine list "alcohol" on the label. Why is it there?

A small piece of sodium is dropped into ethanol. Predict: sodium reacted with water earlier — what now?

Ethanol is a room-temperature liquid and a good solvent — hence tincture of iodine, cough syrups and tonics.

In the second reaction concentrated sulfuric acid acts as a dehydrating agent.

As a fuel: fermenting sugar-cane molasses gives ethanol, blended into petrol; it burns to CO₂ and water only. In medicines it is the solvent.

Level 1 Why is a blue dye added to denatured alcohol?

Level 2 How is ethene prepared from ethanol? Give the equation and conditions.

Level 3 Both ethanol and water give H₂ with sodium. Does that make ethanol an acid? How would litmus decide?

6. Ethanoic acid, CH₃COOH

Why does pure ethanoic acid freeze in a cold winter room — before water would?

Test dilute ethanoic acid and dilute HCl with universal indicator. Predict the lower pH.

A 5–8% solution in water is vinegar, a preservative. The pure acid melts at 290 K, so in cold weather it freezes and looks like ice — glacial acetic acid.

Esters are sweet-smelling — perfumes and flavourings. The CO₂ above turns limewater milky.

Answer: 290 K is about 17°C, while water freezes at 273 K (0°C) — so the acid solidifies first.

Level 1 What is vinegar, and at what concentration?

Level 2 How are esterification and saponification related?

Level 3 Two unlabelled bottles hold ethanol and ethanoic acid. Identify them using only baking soda.

7. Soaps and detergents

Back to the opening question — why does soap remove an oil stain when water alone cannot?

1. Two glasses, each half full of water plus two drops of cooking oil.
2. Add a little soap solution to one only.
3. Stir both hard, then let them stand for two minutes.

Second test: the same soap in rainwater and in well water. Which lathers faster?

Soaps are the sodium or potassium salts of long-chain carboxylic acids. Each molecule has two ends: an ionic head that dissolves in water (hydrophilic) and a long hydrocarbon tail that dissolves in oil (hydrophobic).

Soap molecules surround the dirt — tails in the oil, heads in the water. This cluster is a micelle; rinsing carries it away.

Full answer: water cannot grip oil; the soap molecule is a bridge — tail holds the oil, head the water. Where water is hard, detergents dominate, because soap would be wasted as scum.

Level 1 What does soap form in hard water?

Level 2 Explain micelle formation with a labelled diagram. (3 marks)

Level 3 A solution lathers very little with soap. Give two possible causes and say how you would tell which it is.

Your ladder — score yourself

How many of the seven "Check" questions were right at each level?

The trap table

Diagrams to draw, and how marks are awarded

Example mark scheme (typical practice, not an official scheme)

Final test — mixed, including earlier topics

Earlier topics are mixed in. 8+ correct = solid.

1. What is the valency of carbon?
2. Formula of ethyne and the bond type in it?
3. How many isomers does C₄H₁₀ have?
4. Name CH₃CHO.
5. One industrial use of an addition reaction?
6. Why is it called glacial acetic acid?
7. How do you recognise an ester?
8. Why do detergents work in hard water?
9. (acids topic) How do you test for CO₂?
10. (metals topic) Solid NaCl does not conduct, yet methane never conducts in any state. Why the difference?

Glossary

For parents and teachers

A. The shape of methane

Figure 2 drew methane flat, with four bonds at right angles. That is a convenience of paper. A real methane molecule is tetrahedral: the four hydrogens sit at the corners of a triangular pyramid, about 109.5° apart. ^[1]

The reason is simple repulsion — four bonding pairs of electrons push as far from each other as they can, and in three dimensions that is the tetrahedron. This idea, called VSEPR (valence shell electron pair repulsion), is taught in most Grade 11 and US honors courses. ^[1] It also explains why long carbon chains zig-zag rather than lie straight.

B. Why life is built on carbon, not silicon

Part 1 noted that silicon catenates only up to about seven or eight atoms. That single sentence sits on top of one of the biggest questions in astrobiology — because silicon is roughly 150 times more abundant in the Earth's crust than carbon, yet life chose carbon.

A 2024 NASA technical review of "life as we don't know it" sets out the chemistry: Si–Si bonds are far more reactive than C–C bonds in water, and silicon is largely unavailable for biochemistry on Earth because it locks itself into chemically stable minerals — sand and rock. ^[2] Bond-energy tables tell the same story: a C–C bond is substantially stronger than a Si–Si bond. ^[1]

C. From ethene to plastics

In Part 1, ethene added hydrogen across its double bond. That same double bond can instead open and join to another ethene molecule, and then another, thousands of times over. The result is a long chain — polythene. ^[1]

This is addition polymerisation: many small molecules (monomers) becoming one very large molecule (a polymer), with nothing left over. ^[1] Nearly every plastic around you — bags, bottles, pipes — comes from unsaturated hydrocarbons treated this way. The property that makes plastics so useful, the strength of the carbon chain, is also why they persist so long in the environment.

D. Ethanol as a fuel, worldwide

NCERT mentions ethanol blended into petrol. The scale is larger than most students imagine. According to the United States Department of Energy, more than 98% of US petrol contains ethanol, usually as E10 — 10% ethanol, 90% petrol — which reduces air pollution. ^[3]

The same source notes that ethanol has the identical chemical formula whether it is made from maize, as in the United States, or sugar cane, as in Brazil, or from wood chips and crop residues. ^[3] Your CH₃CH₂OH is the same molecule in every case — a neat demonstration that chemistry does not care about geography.

E. Where this leads

References

Only universities and government agencies are cited. Each link was checked when this guide was written.

1. Chemistry LibreTexts — open textbook project hosted by the University of California, Davis. Chapters on VSEPR and molecular shape, bond energies, and addition polymers. chem.libretexts.org
2. Grefenstette, N. et al. "Life as We Don't Know It" (2024), Chapter 9. NASA Technical Reports Server. ntrs.nasa.gov
3. United States Department of Energy, Alternative Fuels Data Center. "Ethanol Fuel Basics." afdc.energy.gov
4. PhET Interactive Simulations, University of Colorado Boulder. "Build a Molecule", CC-BY 4.0. phet.colorado.edu
5. National Council of Educational Research and Training (NCERT), Government of India. Science — Textbook for Class X. ncert.nic.in

About this guide