Examples of heat of vaporization in the following topics:
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- Evaporation of water requires a substantial amount of energy due to the high heat of vaporization of water.
- As a result of the network of hydrogen bonding present between water molecules, a high input of energy is required to transform one gram of liquid water into water vapor, an energy requirement called the heat of vaporization.
- Water has a heat of vaporization value of 40.65 kJ/mol.
- They depend only on the vapor pressure of water.
- Explain how heat of vaporization is related to the boiling point of water
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- The latent heat is the energy associated with a phase change of a substance.
- The heat Q required to change the phase of a sample of mass m is given by
- where the latent heat of fusion, Lf, and latent heat of vaporization, Lv, are material constants that are determined experimentally.
- The system is constructed so that no vapor evaporates while ice warms to become liquid water, and so that, when vaporization occurs, the vapor remains in of the system.
- The long stretches of constant temperature values at 0ºC and 100ºC reflect the large latent heat of melting and vaporization, respectively.
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- Water transitions from ice to liquid to water vapor as heat is added to it.
- A constant rate of heating is assumed, so that one can also think of the x-axis as the amount of time that goes by as a substance is heated.
- Liquid water becomes water vapor or steam when it enters the gaseous phase.
- Use the heat of vaporization ($\Delta H_{vap}$ ) to calculate how much heat was absorbed in this process: $q=m\cdot C_{H_2O(g)}\cdot \Delta T$, where m is the mass of the sample of water.
- After breaking the bonds, heat is then absorbed and converted to increased kinetic energy of the molecules in order to vaporize them.
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- The solid has such high vapor pressures that heating leads to a substantial amount of direct vaporization even before the melting point is reached.
- The enthalpy of sublimation (also called heat of sublimation) can be calculated as the sum of the enthalpy of fusion and the enthalpy of vaporization.
- Even ice has a measurable vapor pressure near its freezing point, as evidenced by the tendency of snow to evaporate in cold dry weather.
- There are other solids whose vapor pressure overtakes that of the liquid before melting can occur.
- Notice the triple point of the substance.
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- Vaporization of a sample of liquid is a phase transition from the liquid phase to the gas phase.
- Vaporization of a sample of liquid is a phase transition from the liquid phase to the gas phase.
- This is because the liquid can be heated less in order for its vapor pressure to equal the atmospheric pressure.
- If the vapor pressure of the drop is greater than the partial pressure of vapor in the gas phase, the drop will evaporate.
- Run the model, then heat the liquids.
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- The amount of water vapor in air is a result of evaporation or boiling, until an equilibrium is reached.
- The expression "it's not the heat, it's the humidity" makes a valid point.
- The amount of water vapor the air can hold depends on its temperature.
- The capacity of air to hold water vapor is based on vapor pressure of water.
- The vapor pressure of water at 100ºC is 1.01×105 Pa, or 1.00 atm.
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- Evaporation is a type of vaporization of a liquid that only occurs on the liquid's surface.
- Usually, the molecules in a glass of water do not have enough heat energy to escape from the liquid.
- With sufficient heat, however, the liquid would quickly turn into vapor.
- Evaporation of water occurs when the surface of the liquid is exposed, allowing molecules to escape and form water vapor; this vapor can then rise and form clouds.
- They depend only on the vapor pressure of water.
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- The vapor pressure of a solution is directly influenced by the number of solute molecules present in a given amount of solvent.
- Vapor pressure is a measure of the tendency of a material to escape into the environment via gas.
- The vapor pressure of a solvent is lowered by the addition of a non-volatile solute to form a solution.
- Raoult's law states that the vapor pressure of an ideal solution is dependent on the vapor pressure of the pure solvent and the mole fraction of the component present in the solution.
- Calculate the vapor pressure of a solution consisting of 3 moles of a nonvolatile solute and 15 moles of water at 25 oC, given that the vapor pressure of pure water at 25 oC is 23.8 torr.
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- Most of the water is in the liquid phase, where it is held by the mutual attraction of water molecules.
- Likewise, every once in a while a vapor molecule collides with the liquid surface and condenses into the liquid.
- If the liquid is heated a little over 100 °C, the transition from liquid to gas will occur not only at the surface, but throughout the liquid volume: the water boils.
- The water vapor in it changes phases.
- Collisions between water molecules in the atmosphere allows some to condense and some to remain in vapor.
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- Example: Calculating Heat Transfer by Convection: Convection of Air Through the Walls of a House.
- The specific heat of air is a weighted average of the specific heats of nitrogen and oxygen, which is c=cp≅1000 J/kg⋅C (note that the specific heat at constant pressure must be used for this process).
- If the water vapor condenses in liquid droplets as clouds form, heat is released in the atmosphere (this heat release is latent heat) .
- Water vapor carried in by convection condenses, releasing tremendous amounts of energy, and this energy allows air to become more buoyant (warmer than its surroundings) and rise.
- Cumulus clouds are caused by water vapor that rises because of convection.