Organic Chemistry Essentials Worksheet

Name:

Date:

Class:

Organic chemistry molecules illustration

🧪 Introduction: What is Organic Chemistry?

Organic chemistry is the branch of chemistry that studies compounds containing carbon. Carbon is unique because it can form long chains, rings, and complex structures by bonding with other carbon atoms and elements such as hydrogen, oxygen, nitrogen, and more. Organic compounds are found everywhere in everyday life — from the petrol used in New Zealand vehicles, to the plastics in our packaging, to the proteins in our food. Understanding organic chemistry helps us make sense of the materials and fuels that shape our world.

📝 Part 1: Multiple Choice

Circle the letter of the best answer for each question.

1. Which of the following best describes a hydrocarbon?

A) A compound containing only hydrogen and oxygen

B) A compound containing only carbon and hydrogen

C) A compound containing carbon, hydrogen, and nitrogen

D) Any compound that dissolves in water

2. Which family of hydrocarbons has the general formula C_nH_2n+2 and contains only single bonds?

A) Alkynes

B) Alkenes

C) Alkanes

D) Aromatics

3. Alkenes are described as unsaturated hydrocarbons. What does this mean?

A) They contain only single bonds between carbon atoms

B) They contain at least one double or triple bond between carbon atoms

C) They cannot burn in oxygen

D) They dissolve easily in water

4. Which functional group is present in alcohols?

A) –COOH

B) –CHO

C) –OH

D) –NH₂

5. When a hydrocarbon undergoes complete combustion, which two products are formed?

A) Carbon monoxide and hydrogen

B) Carbon dioxide and water

C) Methane and oxygen

D) Carbon and steam

6. Which functional group is found in carboxylic acids?

A) –OH

B) –NH₂

C) –COOH

D) –CO–

7. Polymers are large molecules made by joining many smaller units called:

A) Electrons

B) Monomers

C) Isotopes

D) Ions

8. Which of the following is an example of a synthetic polymer commonly used in New Zealand packaging?

A) Glucose

B) Ethanol

C) Polyethylene (plastic)

D) Methane

🔗 Part 2: Matching — Functional Groups

Draw a line from each functional group name on the left to its correct descriptor on the right.

Alcohol

Carboxylic Acid

Aldehyde

Ketone

Amine

Alkene

Contains –NH₂; found in amino acids

Contains –C=C–; unsaturated hydrocarbon

Contains –COOH; acidic, found in vinegar

Contains –OH; e.g. ethanol in hand sanitiser

Contains –CHO; carbonyl group at end of chain

Contains –CO– in the middle of a carbon chain

✏️ Part 3: Short Answer Questions

Answer each question in full sentences where possible.

9. As the number of carbon atoms in an alkane increases, what happens to its boiling point? Give a reason for this trend.

10. Describe two physical properties of alkanes that make them useful as fuels in New Zealand vehicles and home heating.

11. Explain how adding a hydroxyl group (–OH) to a hydrocarbon chain changes the properties of the molecule. Give one example of how this is useful.

12. How does the naming system for alkanes, alkenes, and alkynes change as the number of carbon atoms increases? Complete the table below:

Prefix for carbon count:
1 carbon = meth– | 2 carbons = __________ | 3 carbons = __________ | 4 carbons = __________

Suffix for bond type:
Single bond (alkane) = –ane | Double bond (alkene) = __________ | Triple bond (alkyne) = __________

13. Write the word equation for the complete combustion of methane (the main component of natural gas used in NZ homes).

14. Explain why incomplete combustion is dangerous. What harmful product can be produced?

🔬 Part 4: Identify the Molecule

Look at each molecular formula below. Identify the hydrocarbon family OR the functional group present. Write your answer on the line provided.

15. For each formula, write the name of the hydrocarbon family or functional group, and one key feature that helped you identify it.

a) C₅H₁₂ (fits C_nH_2n+2)

Family/Group: _________________________ Key feature: _________________________

b) C₂H₄ (fits C_nH_2n)

Family/Group: _________________________ Key feature: _________________________

c) CH₃OH

Family/Group: _________________________ Key feature: _________________________

d) CH₃COOH

Family/Group: _________________________ Key feature: _________________________

🌿 Part 5: Creative Task — Polymers in Action

Think about the role of synthetic polymers (plastics) in everyday New Zealand life.

16. Design or describe a real or imagined product made from a synthetic polymer (e.g. a reusable drink bottle, food packaging, a piece of sports gear). In your response:

    • Name or describe the product and the polymer it is made from (e.g. polyethylene, polypropylene, PET)
    • Explain one benefit of using this polymer for this product
    • Explain one environmental consideration related to this polymer in a NZ context

My product: _____________________________________________

Polymer used: _____________________________________________

Optional: Sketch your product in the box below.

📋 Answer Guide — Teacher Use Only

For teacher reference. Do not distribute to students.

Part 1: Multiple Choice

1. B | 2. C | 3. B | 4. C | 5. B | 6. C | 7. B | 8. C

Part 2: Matching

Alcohol → Contains –OH; e.g. ethanol in hand sanitiser
Carboxylic Acid → Contains –COOH; acidic, found in vinegar
Aldehyde → Contains –CHO; carbonyl group at end of chain
Ketone → Contains –CO– in the middle of a carbon chain
Amine → Contains –NH₂; found in amino acids
Alkene → Contains –C=C–; unsaturated hydrocarbon

Part 3: Short Answers

9. Boiling point increases as carbon chain length increases. Longer chains have greater London dispersion (van der Waals) forces between molecules, requiring more energy to separate them.

10. Accept any two: flammable (release energy when burned), liquid at room temperature (easy to store/transport), relatively stable, reasonable energy density. E.g. petrol (octane) and LPG (propane/butane).

11. Adding –OH increases polarity and the ability to form hydrogen bonds, making the molecule more soluble in water and raising its boiling point compared to the equivalent alkane. Example: ethanol (hand sanitiser, disinfectant) mixes with water easily.

12. Prefixes: 2 = eth–, 3 = prop–, 4 = but–. Suffixes: double bond = –ene, triple bond = –yne.

13. Methane + oxygen → carbon dioxide + water (CH₄ + 2O₂ → CO₂ + 2H₂O)

14. Incomplete combustion produces carbon monoxide (CO), a colourless, odourless, toxic gas that can cause poisoning or death. It occurs when there is insufficient oxygen for complete combustion.

Part 4: Identify the Molecule

a) Alkane — fits C_nH_2n+2; only single bonds, saturated
b) Alkene — fits C_nH_2n; contains a C=C double bond, unsaturated
c) Alcohol — contains –OH functional group (methanol)
d) Carboxylic acid — contains –COOH functional group (ethanoic acid / acetic acid / vinegar)

Part 5: Creative Task

Accept any reasonable polymer product. Look for: named polymer (e.g. PET, polyethylene, polypropylene, nylon), a clear benefit (durable, lightweight, waterproof, cheap to produce), and a genuine environmental consideration (e.g. slow to biodegrade, contributes to landfill/ocean pollution, recycling challenges in NZ, carbon footprint of production). Award marks for scientific reasoning and NZ context.