Have you ever wondered why ice melts into water or water boils into steam? What causes these changes in the state of matter? The answer is temperature. Temperature is a measure of how hot or cold something is, and it affects the physical properties of matter. In this article, we will explore how temperature is related to the physical change of a substance, and what happens when matter changes from solid to liquid, liquid to gas, or vice versa.
Contents
What is a Physical Change?
A physical change is a change in the appearance or form of a substance, but not in its chemical composition. For example, when you cut an apple into slices, you are changing its shape and size, but it is still an apple. A physical change can also involve a change in the state of matter, such as melting, freezing, vaporization, condensation, sublimation, or deposition. A change in the state of matter occurs when a substance changes from solid to liquid, liquid to gas, or gas to solid.
How Does Temperature Affect the State of Matter?
The state of matter of a substance depends on how fast its molecules are moving and how closely they are packed together. Temperature affects both of these factors. Temperature is related to the kinetic energy of molecules, which is the energy of motion. When you heat up a substance, you are increasing its kinetic energy, which means its molecules move faster and farther apart. When you cool down a substance, you are decreasing its kinetic energy, which means its molecules move slower and closer together.
The state of matter of a substance also depends on the intermolecular forces between its molecules, which are the attractions that hold them together. Different substances have different intermolecular forces, which determine how much kinetic energy they need to change state. For example, water has strong intermolecular forces called hydrogen bonds, which make it harder to separate its molecules than other liquids.
When the kinetic energy of a substance is high enough to overcome its intermolecular forces, it changes state. For example, when you heat up ice, you are increasing its kinetic energy until it reaches its melting point, which is the temperature at which it changes from solid to liquid. When you heat up water, you are increasing its kinetic energy until it reaches its boiling point, which is the temperature at which it changes from liquid to gas.
What Happens During a Change in State?
During a change in state, a substance absorbs or releases energy from or to its surroundings. This energy is called latent heat, which is the amount of energy needed to change the state of one gram of a substance without changing its temperature. For example, when ice melts into water at 0°C, it absorbs 334 joules of energy per gram from its surroundings. This energy is used to break the intermolecular forces that hold the ice crystals together. When water vaporizes into steam at 100°C, it absorbs 2260 joules of energy per gram from its surroundings. This energy is used to overcome the intermolecular forces that keep the water molecules together.
The opposite happens when a substance changes state from gas to liquid or liquid to solid. It releases latent heat to its surroundings as it forms intermolecular bonds. For example, when steam condenses into water at 100°C, it releases 2260 joules of energy per gram to its surroundings. When water freezes into ice at 0°C, it releases 334 joules of energy per gram to its surroundings.
Conclusion
Temperature is related to the physical change of a substance because it affects the kinetic energy and intermolecular forces of its molecules. When a substance changes state from solid to liquid or liquid to gas, it absorbs latent heat from its surroundings as it breaks intermolecular bonds. When a substance changes state from gas to liquid or liquid to solid, it releases latent heat to its surroundings as it forms intermolecular bonds.
