1. a)
- QR: Liquid, only
- RS: Phase change
- ST: Gas, only
b) As heat is added during section QR, the water molecules gain kinetic energy and move faster, but they remain in the liquid state.
c) During section RS, the added heat energy is used to break the intermolecular forces holding the water molecules in the liquid phase, allowing them to transition into the gas phase. The temperature remains constant as this phase change occurs.
2. (1) 55°C
3. During line segment DE, the substance is undergoing a phase change from liquid to gas (boiling).
4. At point F, the particles are widely spaced and moving rapidly in random directions, representing the gaseous state.
5. During line segment BC, the substance is melting. Energy is being absorbed to overcome intermolecular forces, allowing particles to move from fixed positions in the solid lattice to a more mobile arrangement in the liquid state, while the temperature remains constant.
6. The heating curve for pure water between -10°C and 110°C includes:
- A sloping line from -10°C to 0°C (solid/ice)
- A horizontal line at 0°C (melting/freezing point, solid to liquid)
- A sloping line from 0°C to 100°C (liquid/water)
- A horizontal line at 100°C (boiling/condensation point, liquid to gas)
- A sloping line from 100°C to 110°C (gas/steam)
Parent Tip: Review the logic above to help your child master the concept of heating curve worksheet answers.
