Latent heat, heat of fusion, heat of vaporization problems. Flexible learning approach to physics eee module p7. Find out the rate which is proportional to heat transferred through the surface of the sphere solution. Pdf exact solution for a twophase stefan problem with. A spherical constant temperature heat source of radius r 1 is at the center of a uniform solid sphere of radius r 2. Latent heat, heat of fusion, heat of vaporization problems and solutions free download as pdf file. Pv diagram problems and solutions in this page we have pv diagram problems and solutions on heat and thermodynamics for jee and competitive examinations. Latent heat is the amount of heat added to or removed from a substance to produce a change in phase.
Latent heat, heat of fusion, heat of vaporization problems and solutions. An energy transfer is heat transfer when its driving force is temperature difference. Calculate the amount of heat added to 1 gram gold to change phase from solid to liquid. Latent heat of condensation enthalpy of condensation.
This paper is concerned with a reliable treatment of the stephan problem with variable latent heat. For a transition from solid to liquid, l is known as the latent heat of fusion, l. Chapter 1 basics of heat transfer 1e a logic chip in a computer dissipates 3 w of power. How much steam at 100 is needed to just melt 5 kg of ice at 15c. In order to melt one gram of ice into liquid water at 0 c, 334 j of heat must be absorbed, or in order to freeze 1 g of liquid water into ice at 0 c 334 j of heat must be released. This physics video tutorial explains how to solve problems associated with the latent heat of fusion of ice and the latent heat of vaporization of ice. It is also known as enthalpy of vaporization, with units typically given in joules j or calories cal. It could either be from a gas to a liquid or liquid to solid and vice versa. Also, an analytical solution based on a similarity variable is presented in the case when the dirichlet boundary condition at the waterice interface depends on time. The heat gained by the ice will be equal to the heat lost by the coffee.
A body with mass 2 kg absorbs heat 100 calories when its temperature raises from 20oc to 70oc. The amount of heat required to change the state of unit mass of a solid to liquid at constant temperature at its melting point or vice versa is known as latent heat capacity of fusion or solidification. Table of contents show 1 ncert exemplar problems for class 9 science. Latent heat storage is a popular research area with industrial and domestic applications, such as energy recovery of airconditioning and underfloor electric heating by using a phase changing material. The heat it removes is the latent heat required to change the sweat from a liquid to gas. The most practicable routes of latent heat storage are solid to liquid and solid to solid.
Sensible heat, latent heat and specific heat engineers gallery. The latent heat is the heat released or absorbed per unit mass by a system in a. Question 1 calculate the energy released when a 10 g water at 100 c and b 10 g of steam at 100 c are each spilt on the hand. The specific heat of ice is 2060 jkg c, the initial temperature is 10 and the final temperature is 0. We consider isolated systems, unless otherwise stated, so that no heat is lost to the environment and the principle of. Large volume changes render such systems complex and impractical. On the solutions of a stefan problem with variable latent heat. Dec 04, 2019 calculate the specific latent heat of vaporsation of steam given. Lastly, the specfic latent heat of vapourization lv is the thermal energy required for 1kg of the substance to boil or condense. Latent heat of fusion and vaporization, specific heat. If the system as a whole is at rest, so that the bulk mechanical energy due to translational or rotational motion is zero, then the. Latent heat is associated with processes other than changes among the solid, liquid, and vapour phases of a single substance. The usual units used for quantities in this equation are degrees celsius for temperature sometimes kelvin, grams for mass, and specific heat reported in caloriegram c, joulegram c, or joulegram k. Latent heat problems flashcards create, study and share.
Indiana chemistry standards resource, november 2003 substance cp jgc water l 4. Phase changes and latent heat how much energy does it take to boil water. Solved problems on specific heat, latent heat and entropy. Why does the temperature of h 2 o not increase when it is boiling. This is the heat per kilogram needed to make the change between the liquid and gas phases, as when water boils or when steam condenses into water.
Where, the specific latent heat is l, heat is q, and mass of any substance is m. To leave a comment or report an error, please use the auxiliary blog. Take the specific heat capacity of water to be 4200 j kg 1 k 1 and the specific latent heat of vaporisation of water to be 2. Students know how to solve problems involving heat flow and temperature changes, using known values of specific heat and latent heat of phase change. Calculate the energy taking place when a substance changes state. The rate h at which heat is transferred through the. Water leaves a hose at 20oc and is converted by the heat from the fire into steam at 300oc. The method is examined for computational efficiency and accuracy. How much heat is needed to convert 1 kg of ice at 10oc to steam at 100oc. Calculate the specific latent heat of vaporsation of steam given. The rate h at which heat is transferred through the slab is, a directly proportional to the area a. The first law of thermodynamics work and heat are two ways of transfering energy between a system and the environment, causing the systems energy to change.
Specific latent heat describe what is meant by specific latent heat of fusion and specific latent heat of vaporisation. How latent heat of vaporisation is used to run trains and machines asked by lovemaan5500 23rd november 2017 7. How to calculate the latent heat needed to cause a phase. Specific heat and latent heat use the table and equations to solve the problems below.
This assumption is pragmatic in the absence of relevant data. Note that the enthalpy of condensation or heat of condensation is by definition equal to the enthalpy of vaporization with the opposite sign. The latent heat of vaporization of water is 2260 jg. Attached is a list of needed values to solve problems 1. The heat thermal energy required for an objects phase transition is. Specific latent heat examples, solutions, videos, notes.
Latent heat, heat of fusion, heat of vaporization problems and. Physics 0608 the 1st law of thermodynamics and simple processes. Icse solutions for class 10 physics specific heat capacity. Latent heat is defined as the heat or energy that is absorbed or released during a phase change of a substance. We can use the table table 1 above and the equations below to calculate specific latent heat. What amount of heat is removed from the fire by 1 tonne kg of water. Latent heat energy must be removed from substance example how much heat is released from 50g of water as it a changes from liquid to ice at 0oc. Hope you like them and do not forget to like, social share and comment at the end of the page. The process of dissolving one substance in another often involves heat. Latent heat definition, types, formula, fusion and. Heat of vaporization is the amount of heat energy required to change the state of a substance from a liquid into a vapor or gas. It varies with the type of material and the nature of the phase transition. Scroll down the page for more examples and solutions on how to use the formula.
Ncert exemplar problems solutions class 9 science pdf format are available to download. In order to extract the maximum flavor in the shortest amount of time, your local fast food purveyor has decided to brew its coffee at 90 c and serve it quickly so that it has only cooled down to 85 c. Solidtogas and liquidtogas transitions have a higher latent heat of fusion, but their large volume expansion, associated with containment problems, rule out their potential use in thermal storage systems 58. Latent heat is related to a heat property called enthalpy. Find out the rate which is proportional to heat transferred through the surface of the sphere. In order to extract the maximum flavor in the shortest amount of time. The latent heat for vapourisation of pure water is used, even though the water will be evaporating from a moderately concentrated or saturated solution at the later stages of evaporation in the model. Sensible heat, latent heat and specific heat engineers. Schroeder, an introduction to thermal physics, addisonwesley, 2000 problems 1. To solve latent heat of phase change problems the latent heat of fusion of water is 334 jg or the latent heat of vaporization of water is 2260 jg. In the chart in figure 2 notice that temperature is plotted on the left margin, and heat content is plotted along the bottom of the chart. To condense 1 g of steam into liquid water at 100 c, 2260 j of heat energy must be released. This energy is the latent heat of evaporation it is latent meaning hidden in that during the phase change the measurable temperature sensible heat of the liquid does not change.
Latent heat and evaporation je2f for a liquid to evaporate into a gas vapor, energy must be added to break the molecular bonds of the liquid. Problems of specific and latent heat 1 a 250g piece of gold is at 19 c. The amount of heat assimilated or discharged by a substance experiencing a change of state, for example, ice changing to water or water to steam, at consistent temperature and pressure. If there is no heat loss to the surroundings, the heat released by the condensation of m 1 g of steam at 100c into water at 100c can be used to. Assumptions heat transfer from the surface is uniform. Chemistry latent heat of phase change problems 2011. Specific heat and heat capacity problems and solutions. Physics 0609 the 2nd law of thermodynamics and heat.
Latent heat of vaporisation of water 2260 kjkg ospecific heat of steam 2. Mech302heat transfer homework10 solutions problem 10. The following example describes the sensible heat and latent heat characteristics of 1 lb of water at standard atmospheric pressure from 0f through the temperature range to above the boiling point. However, an important point that we should consider regarding latent heat is that the temperature. Q coffee this mixing problem is more complicated than the ones in the previous section, however. The amount heat dissipated in 8 h and the heat flux on the surface of the chip are to be determined. Specific heat problems 1 how much heat must be absorbed by 375 grams of water to raise its temperature by 25 c. Explain your answer by drawing a heatingcooling curve for water. Heat to raise temperature of water from 20oc to 100oc x 4. Many solids exist in different crystalline modifications, and the transitions between these generally involve absorption or evolution of latent heat. Latent heat definition, types, formula, fusion and vaporization. For condensation, latent heat effects associated with the phase change are significant, similarly as for boiling, but in reverse. The following diagram shows the formula for specific latent heat. Ncert exemplar problems class 9 science solutions in pdf.
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