Temperature Heat and Thermal Energy

in this video we're going to look at temperature heat and thermal energy and the main idea is that heat is transfer of thermal energy that occurs spontaneously from warmer object to cooler object few essential questions we're going to answer our how our temperature and thermal energy related how our thermal equilibrium and temperature related how is thermal energy transferred and what is specific heat this is the very important part the specific heat that's the math portion of this video few new terms that we might look at our thermal conduction thermal equilibrium heat convection radiation and specific heat and also review the idea of thermal energy so thermal energy like macroscopic objects particles can have kinetic and potential energy so we can think of very small particles having this same type of kinetic or potential energy gas particles can collide with each other or the walls of the container resulting in transfer of this energy and because there are many particles and many collisions in sample of gas it's convenient to discuss the total energy of the molecules and the average energy per molecule the sum of the particles energy is called the thermal energy whereas the average is called the temperature and so there's distinct difference between these two the total energy of all the particles is thermal energy but the average energy per particle is called the temperature say we have helium-filled balloon and it's kept inflated by repeated pounding from the helium atoms on the balloon wall and the size and temperature of the balloon are affected by the average kinetic energy of the helium atoms and if you put that balloon in the sunlight energy is absorbed from the Sun and it makes each of these helium atoms move faster and faster in random directions and bounce off the rubber walls of the balloon more often causing the balloon to expand so when the temperature increases the average energy increases so we get an expansion of the balloon well conversely if we refrigerate the balloon it shrinks because the particles are moving more slowly and the refrigeration has removed some of the thermal energy of the helium the atoms in solid also have kinetic energy but they are unable to move freely as they do in gas sample one way to illustrate the molecule structure of solid is to picture the number of atoms that are connected to each other by Springs because of the springs the atoms bounce back and forth with some bouncing more than others and each atom has kinetic energy and some potential energy from these Springs that are attached to it and if solid has number of atoms then the total thermal energy and the solid is equal to the average kinetic energy plus the potential energy per atom times so that's our number of atoms in particular solid now keep in mind there are not actually Springs attached to the molecules in solid however they do kind of vibrate back and forth as if we had little mass attached to spring and it would be that very similar vibration and so we consider them to have these spring-like connections on average if we have particle in hot object it's going to have more kinetic energy than particle in cold object however this does not mean that each of the particles that compose of an object has the same amount of energy the particles that compose an object don't have the same amount of energy they actually have very wide range of energy so you have an object on table that has given temperature not every particle in that object is going to have the same amount of energy there's going to be wide range remember temperature is the average of all the energies temperature does not depend on the number of particles in the object however the thermal energy of the object does depend both its temperature and the number of particles because temperatures average thermal energy is total so if we have two muffins small muffin large muffin they may be at the same temperature but the large muffin has much more thermal energy than the small muffin does you've probably used the thermometer before to use temperature or you least see thermometers in in your everyday life measuring temperature and the atomic level process involved in measuring temperature involves collision and energy transfer between the thermometer and its surroundings when the cold glass tube of the thermometer touches something that is warmer than the glass the faster moving particles of the surroundings collide with the slower moving particles of the glass energy is then transferred from the surroundings to the glass particles by the process of thermal conduction so any time we touch this is conduction which is the transfer of thermal energy when particles collide and the thermal energy of the particles that make up the thermometer increase while at the same time the thermal energy of the particles of the surroundings decreases now the the thermal energy is decreasing the surroundings vary slightly because the thermometer is small object whereas the surroundings typically are going to be much bigger object so you won't necessarily notice that decrease in thermal energy of the surroundings but we do notice an increase in the thermal energy of the kilometer because the reading changes and as the particles in the glass gain more energy they begin to give some of their energy back to the particles of the surroundings at some point the rate of transfer of energy between the glass and the surroundings becomes equal the surroundings of the thermometer are at the same temperature and at this point this is the important part the surroundings and the therm and the thermometer are said to reach thermal equilibrium the state in which the rate of energy flow between two objects is equal and the objects are at the same temperature objects with wide variety of temperatures are present in the universe we see all sorts of different temperatures in just our everyday life on earth and then if we broaden our scope to even space in the entire universe we see very wide range of temperatures temperatures do not appear to have an upper limit they can keep going on and on and on and we see things hotter and hotter and hotter however temperatures do have lower limit and this is known as absolute zero at Absolute Zero all the thermal energy that can be removed from substance has been removed and it is impossible to reduce the temperature any further this can this can be no temperature lower than negative 273 point 15 degrees Celsius in the United States most of the time we give our temperature in Fahrenheit and you also may be familiar with the Celsius scale because lot of countries do use that our neighbors to the north and Canada use Celsius and you can also see that on lot of our thermometers and digital signs you drive down the street and the freezing point of water at sea level is defined to be zero degrees Celsius and the boiling point is defined to be hundred degrees Celsius so Celsius is based off off of water and so at 0 we freeze at 100 we boil and if you notice there are negative temperatures on the Celsius scale which suggests molecule could have negative kinetic energy which is not possible because we know kinetic energy is always positive so the solution to this issue is to use Kelvin scale where the zero point of the Kelvin scale is to be defined at Absolute Zero so each interval on the scale that's the Kelvin scale is equal to 1 degrees Celsius so that means that whatever your temperature is in Celsius if you just add to 73 to it you get the temperature in Kelvin now we're going to bring into the real meat of this video and the idea of heat and transfer of heat and how it affects thermal energy the transfer of thermal energy which occurs spontaneously from hotter object to cooler object is called heat heat like energy and work is measured in joules and we use to signify heat and if has negative value thermal energy has left the object and if has positive value then the object has absorbed thermal energy so we use is the idea of the the transfer of heat and if is positive we increase ques- we decrease so recall that thermal conduction is the transfer of thermal energy that occurs when particles collide so conductions happening when we touch so for instance if we put frying pan on an electric stove that heat from the stove is being transferred into the frying pan and so is positive there for the frying pan because heat is being absorbed into the frying pan there are other ways that we can transfer energy other than just conduction and heating caused by the motion of fluid in liquid or gas due to temperature difference is called convection an example of this would be heating the pot of water thermal energy flows from the rising hot water and the descending cold water so as you heat the water we're heating the pot through conduction most likely if it's sitting on the stove and then the water is is transferring energy within itself through convection and thunder storms and hurricanes our example of large-scale convections this is the the movement of air through through our atmosphere and in changing the temperature however radiation is transfer of energy by electromagnetic waves and we see this every day come when we energy and heat from the Sun radiation does not depend on the presence of matter which is good because otherwise we would not be able to get any of the energy from the Sun because the space between the sudden the earth has very little to no matter in it and the Sun warms the earth from more than 150 million kilometers away using radiation now one of the terms that we're going to use here in this unit of thermal physics is specific heat and this term is very different than than what you may be thinking now some objects are easier to heat than others and you may have found this in your your everyday life you know you'd see that metal heats up very quickly where water takes long time to heat and we call this the specific heat of material and so this is way to quantify that idea that representation of some objects are easier to heat than others and so the specific heat of material is the amount of energy that must be added to the material to raise the temperature unit of mass by one temperature unit in SI units specific heat is measured in Joule per kilogram kilogram Kelvin so the heat required to change the temperature of an object depends on the mass of the object the change in temperature and the specific heat of the substance and so our main equation that we are going to use in this unit is equals MC delta where delta is the change in the temperature so let's look at an example with this so sometimes short-circuit and electrical wiring system can produce enough thermal energy to melt wire how much thermal energy must be transferred to 20 gram piece of copper wire to raise it from room temperature 25 degrees Celsius to its melting temperature of 1,000 85 degrees Celsius so if we look at the situation this is heat going into wire we know the man the initial temperature of the final temperature and we look up the specific heat of copper that will typically be given to you or at least you'll have table that you can look at for the specific heat so we want to find what is well solve for the unknown we use our equation equals MC delta if we plug in all these values we get 8162 jewels now keep in mind we subtracted these temperatures in Celsius and said earlier they need to be in calvin but remember the difference between one degree Celsius 12 degree kelvin they are the same when we're subtracting them because each unit value is the same in Kelvin and Celsius it's just the starting points are different and so we want to check this answer does it make sense yeah he is evaluated or excuse me he is measured in joules so the units are correct and quick estimate if we wanted to look at these values without using calculator you can see it's going to be about 8000 which is close to our answer looking at another example we have 0.25 excuse me 0.025 kilogram block of an unknown substance and this process that we're about to look at here is actually used lot of times to identify unknown metals and so if you have metal substance and we don't know what it's made of we can use this process that we're talking about here to discover the components and so it's at temperature of 82 degrees Celsius and its place in the calorimeter with 0.025 kilograms of water at 22 degrees Celsius the system reaches an equilibrium temperature of 27 degrees Celsius we want to know what is the unknown substance so there's heat transfer going on here so this metal or whatever the substance is we don't know if it's metal or not but it has some amount of thermal energy and then it reaches equilibrium with water which has much lower temperature lower average kinetic energy of particles and so it reaches equilibrium at 27 degrees Celsius we want to know well what is specific heat of that object looking at the heat transfer so heat is going from the unknown substance into the water to reach equilibrium so what we're looking at here we have all of our known values or initial temperature of the water the mass of the water the initial temperature of the unknown substance in the mass of that substance and they both have the same final temperature and we have the specific heat of water once again we can look that up and that's 4000 180 joules per kilogram degree Celsius and so we know the heat transfer from the water is going to equal the heat transfer from the object the unknown object and so we set those two equal to each other the MC delta equals MC delta and so we solve for the see here by dividing the heat of the water by the mass of the unknown object times its temperature difference and we plug in all of our numbers and we get 380 joules per kilogram degrees Celsius and so this corresponds with copper if we look up in table we can see that this is the specific heat of copper so this unknown object is hopefully now after watching this video you are able to answer these essential questions and have general idea of these vocabulary terms thank you