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Chemistry LibreTexts

11: Energy

  • Page ID
    118832
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    • 11.1: Energy and Chemical and Physical Change
      Phase changes involve changes in energy. All chemical reactions involve changes in energy. This may be a change in heat, electricity, light, or other forms of energy.     Reactions that absorb energy are endothermic. Reactions that release energy are exothermic.
    • 11.2: Energy
      When we speak of using energy, we are really referring to transferring energy from one place to another. Although energy is used in many kinds of different situations, all of these uses rely on energy being transferred in one of two ways. Energy can be transferred as heat or as work.
    • 11.3: Temperature: Random Motion of Molecules and Atoms
      Three different scales are commonly used to measure temperature: Fahrenheit (expressed as °F), Celsius (°C), and Kelvin (K).
    • 11.4: Temperature Changes - Heat Capacity
      The specific heat of a substance is the amount of energy required to raise the temperature of 1 gram of the substance by 1 degree Celsius.
    • 11.5: Energy and Heat Capacity Calculations
      Heat is a familiar manifestation of transferring energy. When we touch a hot object, energy flows from the hot object into our fingers, and we perceive that incoming energy as the object being “hot.” Conversely, when we hold an ice cube in our palms, energy flows from our hand into the ice cube, and we perceive that loss of energy as “cold.” In both cases, the temperature of the object is different from the temperature of our hand.
    • 11.6: Phase Changes
      Fusion, vaporization, and sublimation are endothermic processes, whereas freezing, condensation, and deposition are exothermic processes. Changes of state are examples of phase changes, or phase transitions. All phase changes are accompanied by changes in the energy of a system. Changes from a more-ordered state to a less-ordered state (such as a liquid to a gas) are endothermic. Changes from a less-ordered state to a more-ordered state (such as a liquid to a solid) are always exothermic.
    • 11.7: Evaporation and Condensation
      Evaporation is the conversion of a liquid to its vapor below the boiling temperature of the liquid. Condensation is the change of state from a gas to a liquid. As the temperature increases, the rate of evaporation increases.
    • 11.8: Melting, Freezing, and Sublimation
      Phase changes can occur between any two phases of matter. All phase changes occur with a simultaneous change in energy. All phase changes are isothermal.


    11: Energy is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts.

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