Thermal Properties Of Matter

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Common Misconceptions

6 min read

- What you are getting from a statement might not be necessarily true. Let's burst some of the common misconceptions

HIGHER HEAT IMPLIES MORE TEMPERATURE:

We all are misconceived by the fact that hotter the substances more will be the temperature, but it is not the case. Heat and Temperature are two different things. The heat of an object is the total energy of all the molecular motion inside that object. Temperature is the measure of the thermal energy or average heat of the molecules in a substance. When two bodies are kept in thermal contact, the one with higher temperature will transfer energy to the other by heat. Let us consider we have a metal block and a plastic block. What do you think will be more colder? If your answer is metal then you are right. But if we are trying to check the temperature of both the blocks we will find that the temperature reading of both the blocks are somewhat same. This is because, even though both are at same temperature when we touch them with our fingers there is gain in heat from plastic block to our fingers and loss of heat from our finger to metal block since it conducts heat. That makes us feel a substance hotter or cooler. So this clearly shows that Heat does not directly implies the temperature.

GETTING BURNT BY BOILING WATER IS MORE PAINFUL THAN STEAM:

We always have heard people saying about getting burnt by boiling water, but there are also few instances about getting burnt by steam. So it gave us a understanding that getting burnt by boiling water is much more painful than steam, but it is a clear misconception. This is so because when 1 gram of steam at 100 degree Celsius gets converted to water at 100 degree Celsius, there is a release of heat. The heat evolved is approximately equal to 536 calories. This clearly shows that steam at 100 degree Celsius has more internal energy than that of water at 100 degree Celsius. Hence, it is more painful to get burnt by steam rather than by boiling water at same temperature.

HEAT REQUIRED TO CONVERT LIQUID TO VAPOR IS LESS THAN SOLID TO LIQUID:

We always tend to think that whenever liquid is converted into steam it requires less heat, but this not true. Lets talk about the concept of latent heat. Latent heat is defined as heat energy that is absorbed or released during the transition phase of a substance. It can be either the transition of gas to a liquid or a liquid to a solid or vice-versa. Latent heat of fusion is the quantity of heat required to change the phase from solid to liquid and latent heat of vaporization is the quantity of heat required to change the phase from liquid to gas. When a substance gets converted from liquid to vapor, there is a large increase in volume. Hence more amount of heat is required. But when a solid gets converted o a liquid, then the increase in volume is negligible. hence, very less amount of heat is required. We can say that the latent heat of vaporization is more than the latent heat of fusion. Therefore the heat required to convert liquid to steam is more than heat required to convert solid to liquid.

THE RATE OF THERMAL EXPANSION IS DIFFERENT FOR SOLID MATERIAL AND HOLLOW MATERIAL:

Let us consider a solid sphere and a hollow sphere. Assume that both are made of same material and have equal radius. Now, if both the spheres are heated at the same temperature, which sphere do you think will undergo a larger expansion and which one a smaller? If your answer is "hollow sphere will undergo more thermal expansion than solid sphere" then you are wrong. The answer is thermal expansion of both the spheres will be equal, this is because the expansion of isotropic solids is similar to true photographic enlargement. This means the expansion in hollow and solid sphere will be same if both are made up of same material. But to raise the temperature of both sphere with same amount, solid sphere will take more heat because its mass would be more.

MORE COLD FELT AT THE TIME OF ICEMELT RATHER THAN AT THE TIME OF SNOWFALL

People enjoy a lot at the time of snow falling but when snow stops falling and it started to melt then it becomes very difficult to sustain. In the mountain areas (where Only one major source of heat 'Sun' is rarely reached) snowmelt by absorbing large amount of heat from the surrounding and get converted into water. In this process temperature of surrounding decrease time to time. By insufficient availability of sunlight, the temperature goes down in significant amount and it becomes difficult to survive in such scenario.

We have also seen More shivering effect of ice cream on teeth as compared to that of water (obtained from ice). This is because when ice cream melts down it absorbs large amount of heat from teeth.

HOT AND COLD TEMPERATURES ARE PROPERTIES OF MATERIALS:

We feel that metal objects are cold and polystyrene ones are hot (or at least warm) - when they are at room temperature. That is because when we touch objects made of them at room temperature we feel hot or cold to them. The reason why metals feel cold is because they are good conductors - they take heat quickly away from the body - so the sensors in our fingertips relay the information to the brain that we are losing heat energy from our bodies more quickly than before we touched the object. The converse is true with polystyrene, it gives heat to our body making our brain to feel it is hotter. It is all down to heat transfer rate. Hence hot and cold is not the property of the material, its just that the thing about heat transfer.