Particle Movement
Explain why solids keep their shape but gases do not, using particle motion.
Particles in solids vibrate in place and are closely packed; particles in gases move freely and spread out.
Identify whether heat is absorbed or released during condensation and explain particle behavior.
Heat is released; particles slow down and move closer together to form liquid.
Explain why a liquid thermometer rises more in a narrow tube than in a wide tube.
Narrow tube shows expansion more clearly; liquid moves further per unit of volume change.
Explain why ice floats on water using particle arrangement and density.
Ice particles are more spread out than liquid water; lower density makes it float.
Why does a balloon shrink in cold weather?
Particles slow down, move less, contract, reducing balloon volume.
A liquid is heated. Predict how the motion and spacing of particles change, then explain how this leads to a change in volume.
Particles move faster and spread farther apart, causing the liquid to expand slightly.
Ice melts at 0°C but stays at 0°C until fully melted. Explain using particle motion and energy transfer.
Energy goes into breaking bonds between particles, increasing potential energy, not temperature.
A thermometer is placed in ice water and then in boiling water. Explain how scientists calibrate it using these reference points.
0°C is marked at ice melting; 100°C at water boiling; scale is divided into equal increments for intermediate temperatures.
Predict what happens when a metal bridge expands in hot weather.
Metal particles move faster and spread slightly; bridge lengthens; engineers leave gaps to prevent damage.
Explain why puddles evaporate faster on a windy day.
Moving air removes particles that evaporate, increasing rate; particles at the surface escape more easily.
Describe what happens to particles at a molecular level when a gas is compressed.
Particles are forced closer together; they collide more often but do not lose energy.
Water boils at 100°C. Explain why bubbles form inside the liquid and rise to the surface.
Particles gain enough energy to overcome liquid forces; vapor forms bubbles that rise because gas is less dense than liquid.
Describe what happens at the particle level when the thermometer’s liquid contracts in cold weather.
Particles lose energy, move slower, and occupy less space, causing liquid to fall in the tube.
A cube of metal and a cube of wood have the same volume. Predict which sinks in water and explain using density.
Metal sinks (density > water), wood floats (density < water). Density depends on particle spacing and mass.
Predict and explain what happens when you pour hot water over a metal lid to loosen it.
Heat causes metal particles to expand faster than glass; lid expands, loosens.
Compare the motion of particles in a warm solid and a cold liquid. Which has faster-moving particles and why?
The cold liquid’s particles slide past each other, but the warm solid’s particles vibrate faster. The warm solid particles move faster due to added energy.
Evaporation can occur at any temperature. Explain why this is different from boiling.
Only the fastest-moving particles at the surface escape during evaporation; boiling involves all particles gaining enough energy.
Why can two liquids in thermometers (e.g., alcohol vs. mercury) respond differently to the same temperature change?
Different liquids have different expansion rates due to particle size and interactions.
Explain why heating a sealed gas container increases pressure.
Particles move faster, collide more with container walls, increasing pressure; volume may be constant.
A kettle whistles when water boils. Explain what causes the whistling using particle motion.
Steam bubbles rise; high-speed particles collide with kettle spout, producing vibrations (sound).
Explain why increasing temperature always increases particle speed, but does not always cause a change of state.
Temperature increases particle kinetic energy; a change of state only occurs if particles have enough energy to overcome forces holding them together.
Predict what happens to the boiling point of water at high altitudes and explain using particle motion.
Boiling occurs at lower temperatures because lower pressure allows particles to escape more easily.
Design an experiment to measure the temperature of a cup of warm water without using a thermometer. Explain your reasoning.
Example: Use expansion of a liquid in a tube, or melting point of ice as a reference. Must explain how particle expansion/contraction gives measurable change.
Explain why a steel ball might not fit through a metal ring in summer but fits in winter.
Steel expands in heat (particles move faster, spacing increases) and contracts in cold; change in particle spacing affects size.
Explain how understanding particle motion helps engineers design safer bridges, buildings, or pipelines.
Engineers account for expansion/contraction of materials; predict stresses due to particle motion; prevent structural damage.