The end result of increased molecular motion is that the object expands and takes up more space. Mass of the object remains the same, however. Solids, liquids and gases all expand when heat is added. ... Liquids: Liquids expand when heated and they contract when cooled.

Expansion of Matter on Heating

When matter is heated, it tends to expand. This phenomenon can be explained by understanding the behavior of particles within the substance. The expansion occurs due to an increase in the kinetic energy of the particles, leading to greater movement and spacing between them. Different substances have varying expansion coefficients, which determine their expansion on heating. In general, gases expand the most, followed by liquids, and then solids.

Expansion of Gases
Gases exhibit the highest expansion on heating. This is because gas particles have high kinetic energy and are not bound tightly to each other. When heated, the gas molecules move faster and collide with each other more frequently and with greater force. This increased molecular motion causes the gas to expand and occupy a larger volume. The expansion of gases is described by the ideal gas law, which states that the volume of a gas is directly proportional to its temperature.

Expansion of Liquids
Liquids also expand upon heating, but to a lesser extent compared to gases. The particles in a liquid are closely packed but still have some degree of freedom to move. As the temperature of a liquid increases, the kinetic energy of its particles increases, resulting in more vigorous motion. The increased movement causes the liquid to expand, leading to a slight increase in volume. However, the expansion of liquids is generally less noticeable than that of gases.

Expansion of Solids
Solids exhibit the least expansion on heating compared to gases and liquids. The particles in a solid are tightly packed and have limited freedom of movement. When heated, the particles vibrate more energetically within their fixed positions, but the overall arrangement of the solid remains relatively stable. As a result, the expansion of solids is minimal and often difficult to observe without precise measurements.

Expansion Coefficients
The expansion of a substance can be quantified by its coefficient of linear expansion (α), which measures the change in length per unit length per degree Celsius. The coefficient of linear expansion varies for different materials and is typically higher for gases, followed by liquids, and then solids. For example, the coefficient of linear expansion for steel is approximately 12 × 10^-6 per degree Celsius, while for air it is around 3.4 × 10^-3 per degree Celsius.

In conclusion, the expansion of matter on heating is a result of increased kinetic energy and particle motion. Gases expand the most due to their high molecular freedom, followed by liquids, and then solids. The expansion coefficients of different substances determine the extent of their expansion, with gases generally exhibiting the highest coefficients. Understanding the expansion of matter is crucial in various applications, such as in the design of bridges, buildings, and temperature measurement devices.

All states of matter expand when heated and contract when cooled. Gases expand most when heated and solids the least because gas particles are already far apart and are much freer to move.