Exercises

This chunk presents two exercises: the first asks students to convert temperatures from Kelvin to Celsius, and the second asks them to convert from Celsius to Kelvin. The formula to convert Kelvin to Celsius is to subtract 273 from the Kelvin value. Conversely, to convert Celsius to Kelvin, you add 273 to the Celsius value. Students will practice these conversions to understand the relationship between the two temperature scales.

These questions encourage students to think critically about physical changes and diffusion. Naphthalene balls gradually sublimate, transitioning directly from solid to gas without leaving a residue. Similarly, the dispersal of perfume molecules in the air allows us to detect its scent from a distance due to the process of diffusion, where particles spread out from an area of higher concentration to lower concentration.

This exercise asks students to rank substances based on the strength of the forces acting between their particles. Generally, solids have the strongest intermolecular forces, followed by liquids and then gases, which have the weakest. For this list, sugar (a solid) has the strongest attraction, followed by water (a liquid), and then oxygen (a gas), which has the weakest intermolecular forces.

This chunk requires knowledge of the three states of water: liquid, solid, and gas. Water is a liquid at room temperature (25°C), solid (ice) at 0°C, and gas (water vapor) at 100°C. Understanding these transitions is crucial for grasping how temperature affects the state of matter.

For part (a), water is a liquid at room temperature because its particles are not held in fixed positions, allowing it to flow, take the shape of its container, and maintain a consistent volume. In part (b), iron is a solid at room temperature because its particles are tightly packed in fixed positions, lending it a definite shape and volume, resisting forces that might change its structure.

Ice, being a solid, absorbs heat more effectively when it melts due to the latent heat of fusion. This heat is needed to break the bonds between the ice molecules. In contrast, water at the same temperature doesn't absorb the same amount of heat for cooling since it is already in a liquid state—this highlights the difference in energy absorption during state changes.

Steam produces more severe burns than boiling water despite being at the same temperature. This is because steam contains latent heat of vaporization. When steam condenses on the skin, it releases this heat, causing more severe burns than boiling water that simply cools when splashed.

This exercise likely refers to a visual representation of the various states of matter changes, identifying solid, liquid, gas transitions such as melting, freezing, condensation, evaporation, and sublimation. Understanding these terms helps students visualize how matter interacts with temperature.

This activity involves creating a simple model that visually represents how particles behave in solids, liquids, and gases. By physically manipulating the model, students can observe how particles are arranged and how they move, leading to a deeper understanding of matter’s states.