Question 1: Define a simple molecule and give two examples.

Answer: A molecule made up of a small number of atoms held together by covalent bonds; examples include H₂O (water) and CH₄ (methane).

Question 2: Explain how covalent bonds are formed between atoms.

Answer: Covalent bonds form when two atoms share pairs of electrons to achieve a full outer shell, resulting in a stable molecule.

Question 1: Calculate the number of covalent bonds in a molecule of carbon dioxide (CO₂).

Answer: Two covalent bonds (each oxygen atom shares two pairs of electrons with carbon).

Question 2: If a molecule of ammonia (NH₃) has a molar mass of 17 g/mol, what is the mass of 0.5 moles of ammonia?

Answer: 8.5 grams (mass = number of moles × molar mass = 0.5 × 17 g).

Question 1: Describe a safe procedure for demonstrating the formation of a simple covalent molecule in a classroom experiment.

Answer: Use safe, non-toxic chemicals such as water and iodine vapour. Ensure proper ventilation, wear safety goggles and gloves, and handle chemicals with care. Demonstrate the sharing of electrons through a visual model or molecular representation while avoiding direct contact with reactive substances.

Question 2: Identify the variables that need to be controlled when investigating the boiling point of different simple molecules.

Answer: Variables include the atmospheric pressure, purity of the molecules, and the rate of heating.

Question 1: A series of simple molecules (H₂, N₂, O₂, F₂) have boiling points of -253°C, -196°C, -183°C, and -188°C respectively. Explain how molecular size and intermolecular forces influence these boiling points.

Answer: Larger molecules with more electrons generally have stronger London dispersion forces, leading to higher boiling points. Despite similar sizes, F₂ has a higher boiling point than O₂ due to its greater polarizability. Intermolecular forces significantly influence boiling points in simple molecules.

Question 1: Describe the process of covalent bonding in methane (CH₄) and explain how this bonding affects its physical properties.

Answer: Covalent bonding in methane involves the sharing of four pairs of electrons between one carbon atom and four hydrogen atoms, forming four C-H bonds. This creates a stable, low-boiling, and non-conductive molecule with a tetrahedral shape. The shared electrons lead to low intermolecular forces, resulting in methane’s gaseous state at room temperature.

Question 1: Discuss how knowledge of simple molecules like water and carbon dioxide is important in environmental science and industry.

Answer: Understanding water's properties aids in water treatment and conservation. Knowledge of carbon dioxide is crucial for managing greenhouse gas emissions, climate change, and in processes like photosynthesis and carbon capture technologies.