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Heat Energy

Difference between Heat and Temperature
Total kinetic energy (K.E.) of molecules due to vibration is called heat energy.	Heatness or coldness of object is called temperature
Its unit is Joule (J).	Its Unit is 0C or 0K.
It is cause of temperature	It is effect of heat
It is measured by Calorimeter	It is measured by thermometer

Q. Define heat energy?
→ Heat energy of object is the total kinetic energy (K.E.) of the molecules due to vibration present in it. Its unit is calori in CGS and Joule (J) in SI system.

1 calori = 4.2 Joule.

Q. On which factor heat energy depends?

• Number of molecules in matter or mass of matter.
• average of k.E. of molecules.

Q. Write the effect of Heat energy?

• change in volume.
• change in physical state.
• change in temperature.
• change in solubility.
• change in chemical state.
  Q. The tight lid of bottle is heated to open it. Which effect of heat refers this statement, Give reason also?
  → This statement refers the when object heated its volume increases. When objects heated molecules of it vibrate excessively and become as far as possible. So object volume increases.

• → Heat energy depends on total kinetic energy of molecules i.e. heat energy depends on mass of object.
• → Temperature of object depends on average kinetic energy of molecule i.e. temperature doesn't depends on mass of object.
• → Heat energy transfer from a body of higher temperature to lower temperature and always tend to equal temperature to all bodies.
• → Amount of transfer of heat from a body to another body is directly proportional to contact surface area.

Q. Burning matches stick or hot water full of bucket. In which high temperature and in which high heat, why?

→
• Burning matches stick has high temperature because in it molecules have high vibration and more k.E.
• A bucket of water has high heat energy because it has large number of molecules.

Q. A cup of tea and a cup of cock is kept at same place. Why, cup of tea goes on cooling and cup of cock goes on heating ?
→ Cup of tea has higer temperature than environment so heat transfer from cup of tea to environment and cup of tea goes on cooling.
→ Cup of cock has lower temperature than environment so heat transfer from environment to cup of cock and cup of cock goes on heating.
Q. Lid of closely tight bottle is heated to open, why ?
→ When lid is heated it get expansion and bocome a bit loose. So it is easier to open. Therefor lid is heated.
Q. In hot season electricity or telephone wire get more inclied, why ?
→ In hot season due to excessive heat in environment electricity or telephone wire get expansion and hence more inclied.
Q. When solid is heated it is melted, why?
→ When matters are heated vibration of molecules increase and kitenic energy also increases. As a result space between molecules increase and hence they melt.
Q. When liquid are cooled it becomes solid, why?
→ When liquid are cooled vibration as well as kitenic energy decreases. As a result space between molecules decreases and attration force between molecules increase and hence they becomes solid.
Q. Why woolen clothes should be wear in cold season?
→ Woolen is insulator of heat. If we wear woolen cloths heat could not escape from body to surrounding so that body become worm.
Q. In bridge, empty space is made between compartment, why?
→ When vehicles run on bridge due to friction heat energy is produced. Due to excessive heat beam get expanded. During expansion of beam it would not bent so empty space are made. If there is no empty space then during expansion it would bent and may cause accident.
Q. Cloudy night is hot, why?
→ In cloudy night heat reflected from earth again reflected by cloud toward earth and become hot but if there no cloud then heat reflected from earth is absorbed by environment and hence not so hot.
Q. New quilt(sirak) is more wormer than old quilt, why?
→ New quilt has more cotton molecules so there is more air which is insulator of heat. These air prevent transfer of heat from body to environment, so it becomes wormer.
Q. In a cup made by thin paper can boil water but not in a cup made by thick wooden cup, why?
→ When heat is given to water with thin paper cup then heat is transmit to water and temperature of paper cup would not raise to 100⁰c and not burn.
When heat is given to water with thick wooden cup then heat is not transmit to water and temperature of wooden cup raise which would burn to wooden cup.
Q. Same temperature and same mass of water is kept in steel glass and steel wide bowl, which one get cold faster, why ?
→ Water in wide bowl has more surface area contact with environment so it loose more heat to environment and become cold faster than water in steel glass.
Q. When we put hot water in quartz glass it may brust, why?
→ When we put hot water in quart glass, due to high temperature lower part of glass would get expansion but due insulation property of glass heat is not trasfer to upper part of glass and upper part is not get expansion, which cause to brust. Do yourself

• Q. When we sit in shining day it hot. Give reason?
• Q. In hot season, when start fan in becomes colder, why?
• Q. In hot season, dogs bring its tounge outside, why?
• Q. In hot season, water in soil pot is clod, why?
• Q. In cold season, dogs sleep with shrinking, why?
• Q. In cold season, wormer clothes are needed, why?
• Q. In hot season, sweat comes, why?
• Q. In hot season, plants have new leaf, why?
• Q. In cold season, it is good to wear two thin shirt than a single thick jacket, why?
• Q.