The Kinetic Theory of Matter — Reading Comprehension

The kinetic theory of matter describes how all substances are made of extremely small particles, such as atoms or molecules, that are always in motion. This theory helps explain why materials behave differently under various conditions. For example, when perfume is sprayed in one corner of a room, its scent eventually spreads throughout the entire space. Scientists use the kinetic theory to understand the causes behind this and similar everyday phenomena.

Particle Motion and Temperature
Particles in solids, liquids, and gases are never completely still. In solids, particles vibrate in place and are closely packed. In liquids, they move more freely but still remain close together. In gases, particles move rapidly and are far apart. The speed at which particles move is related to temperature. Temperature measures the average kinetic energy of particles. When you add heat to a substance, the particles move faster because they gain energy. For instance, if you place a drop of food coloring in hot water, the color spreads quickly. This happens because the hotter water particles move faster, helping the coloring to disperse rapidly. In cold water, the movement is much slower.

Diffusion and Real-World Examples
One important process explained by the kinetic theory is diffusion. Diffusion is the movement of particles from an area of high concentration to an area of low concentration. In the case of perfume, the scent particles move through the air until they are evenly spread out. This happens because air particles and perfume particles are always bumping into each other and moving around. The rate of diffusion increases with temperature because particles have more energy and move faster. This is also why food coloring spreads more quickly in warm water than in cold water. Scientists have measured that diffusion can be up to twice as fast in hot water compared to cold, depending on the temperature difference.

Broader Implications and Scientific Connections
The kinetic theory not only explains diffusion but also other changes, such as melting, evaporation, and condensation. When heat is added to ice, the particles vibrate so much that they break free from their fixed positions, turning into liquid water. The theory connects to larger scientific principles, like the laws of thermodynamics, which describe how energy moves and changes in systems. Understanding kinetic theory has led to advances in technology, from refrigerators to air conditioning, and helps people make sense of everyday observations, such as why heating a room makes the air feel less dense.

In summary, the kinetic theory of matter provides a powerful explanation for why matter changes and moves. It shows the connection between energy, temperature, and the behavior of particles in different states. This theory is a foundation for many scientific discoveries and real-world technologies.

Interesting Fact: 
At absolute zero (−273.15°C), particles have their lowest possible energy, but they never stop moving completely!

What does the kinetic theory of matter explain?

Which state of matter has particles that vibrate in place and are tightly packed?

What is diffusion?

What happens to particle motion when heat is added to a substance?

What does temperature measure, according to the passage?

Based on the passage, why does food coloring spread faster in hot water than cold?

Why do scientists think diffusion happens faster at higher temperatures?

Which process is NOT explained by the kinetic theory according to the passage?

True or False: Particles in a solid are completely still and never move.

True or False: At absolute zero, particles have their lowest energy but do not stop moving.