Energy and Change Notes

Energy is defined as the ability to do work.
Energy exists in two primary forms: kinetic and potential.
- Potential energy is stored energy.
- Kinetic energy is the energy of motion; the faster an object moves, the greater its kinetic energy.

Heat energy is a type of kinetic energy, specifically related to the movement of particles within a substance.
When a substance is heated, its particles vibrate or move more rapidly.
Example: A hot stove. Macroscopically, the stove appears still, but at the atomic level, the particles on the surface are in rapid motion.
Higher temperatures correspond to greater kinetic energy of particles.

Physical and chemical changes involve energy changes.
Releasing energy: changes that release energy often occur spontaneously. Example: a bicycle rolling downhill.
Input of energy: pushing a bicycle uphill requires an input of energy to move it to a higher-energy state.

Energy changes can take various forms.
Example: A tree grows by absorbing solar energy to convert carbon dioxide and water into plant material. The energy is stored in the plant material.
If the tree is used as firewood, burning it releases the stored potential energy as heat, converting the plant material back into carbon dioxide and water.

High-energy substances (kinetic or potential) are more likely to cause a change.
Stable substances have less energy and are less likely to react.
Substances with a large amount of potential energy are more likely to react.

Example 1: Balancing Rocks
- Balancing rocks contain a deal of potential energy due to their unstable position.
- When the rocks fall, they release this stored energy, resulting in a more stable formation.
Example 2: Mousetrap
- Setting the trap involves storing energy by bending back the spring.
- Releasing the trigger releases the stored energy, snapping the bar with force.
- Once the energy is released, the trap is stable until reset.
General principle: objects tend to move spontaneously from higher to lower potential energy states.

Ethylene oxide is an unstable compound that can react and open to form a more stable product with less potential energy.
Systems generally move toward the lowest energy state possible.
Substances with low energy are considered stable and do not react readily.
The potential energy in a substance is dependent on its structure.

Many chemical changes involve the absorption or release of heat energy.
Exothermic change: Releases heat energy. Example: Burning wood.
Endothermic change: Requires energy to occur. Example: Heating water to convert it to steam.

Reaction: Carbon + Oxygen → Carbon Dioxide + Heat
This reaction releases energy, meaning carbon dioxide has less potential energy than carbon and oxygen.
Carbon dioxide is more stable than carbon and oxygen.
This reaction is exothermic.