3.4 Moving from hot to cold

• Heat is a form of energy
• When energy is added to atoms, they begin to move more rapidly
• The more motion atoms have, the hotter they feel to the touch
• Energy transfer from hot to cold means that energy is transferred from fast-moving atoms to slow-moving atoms
• In energy transfer, fast-moving atoms impact slow-moving atoms, transferring their kinetic energy
• The temperature at which the ice melts is called its freezing point
• When water changes state, it absorbs or releases heat energy
• A substance with a low specific heat capacity changes temperature quickly when heated or cooled
• If two objects with different temperatures come into contact, some heat will flow between them until both reach the same temperature
• Heat energy can be absorbed by an object without changing its temperature if there are no other objects nearby to absorb the heat
• The temperature at which water boils is called its boiling point
• Thermal Energy Transfer: When you feel heat from a hot drink, thermal energy moves from the drink, through the container, and into your hands. This transfer occurs because thermal energy always flows from hotter places to colder places, with "hotter" indicating a higher temperature and "colder" indicating a lower temperature.
• Feeling Cold: Holding ice makes your hand feel cold, but cold itself isn't an energy store. Instead, the sensation occurs because thermal energy transfers away from your hand and into the ice. This transfer reduces the thermal energy in your hand, resulting in the perception of coldness. Holding ice for too long can damage your skin as it depletes the necessary thermal energy.
• Dissipation: Dissipation refers to the spreading out and loss of energy, making it less useful. When thermal energy moves from a hotter place to a colder place, such as from a warm room to the cooler outdoors, we say that thermal energy has dissipated. This process occurs naturally and increases in speed as the temperature difference between hot and cold places grows.
• Energy Conservation: It's important to note that while thermal energy spreads out and moves to colder places, it doesn't disappear or get destroyed. Instead, it simply redistributes. Energy conservation principles dictate that the total energy within a system remains constant over time, even as energy dissipates and spreads out.