00:00:06.140 hi it's mr. Andersen and this is 00:00:08.27000:00:08.280 chemistry essentials video 47 it's on 00:00:10.45900:00:10.469 heat exchange if I were to say don't 00:00:12.23000:00:12.240 touch this iron right here in the middle 00:00:13.87900:00:13.889 it's hot what does that mean well we 00:00:16.16000:00:16.170 know that it has a higher temperature 00:00:17.42000:00:17.430 and therefore it has a higher amount of 00:00:19.58000:00:19.590 average kinetic energy and if you were 00:00:21.47000:00:21.480 to touch it a lot of that energy is 00:00:23.06000:00:23.070 going to be transferred to your hand and 00:00:25.07000:00:25.080 that's going to produce quite a bit of 00:00:26.66000:00:26.670 pain and so if we ever have a warmer 00:00:28.40000:00:28.410 body and a colder body the warmer body 00:00:30.74000:00:30.750 is going to have more kinetic energy and 00:00:32.63000:00:32.640 again that energy is in the molecular 00:00:34.34000:00:34.350 motion or those molecules moving around 00:00:36.31900:00:36.329 and we're going to have more energy in 00:00:38.33000:00:38.340 that than the colder body and so a good 00:00:40.34000:00:40.350 way to represent that and I'll use this 00:00:42.35000:00:42.360 model over the next few videos is just 00:00:44.29900:00:44.309 using these little cubes that represent 00:00:46.36900:00:46.379 the amount of energy in this case that's 00:00:48.11000:00:48.120 going to be thermal energy and so if I 00:00:50.29900:00:50.309 were to put those two objects in contact 00:00:52.70000:00:52.710 with one another that energy is going to 00:00:55.04000:00:55.050 be transferred in other words energy is 00:00:57.02000:00:57.030 moving from that first object to that 00:00:58.97000:00:58.980 second object and we call that transfer 00:01:01.52000:01:01.530 heat and so what we're really doing is 00:01:03.59000:01:03.600 transferring energy as thermal energy or 00:01:06.08000:01:06.090 heat now heat if you were to look up 00:01:07.88000:01:07.890 heat on the periodic table you're simply 00:01:10.07000:01:10.080 not going to find it there because it's 00:01:11.39000:01:11.400 not a substance it's not a thing it's 00:01:13.31000:01:13.320 just the transfer of energy and so a 00:01:15.32000:01:15.330 good way to think about that and this 00:01:16.91000:01:16.920 should be a sentence that should kind of 00:01:18.64900:01:18.659 roll off your tongue 00:01:19.42000:01:19.430 energy is being transferred as heat 00:01:21.59000:01:21.600 that's really what's going on and so 00:01:24.14000:01:24.150 when we're looking at energy being 00:01:26.17900:01:26.189 transferred as heat it's going to vary 00:01:27.92000:01:27.930 depending on the substance that we're 00:01:29.63000:01:29.640 dealing with in other words metals are 00:01:32.48000:01:32.490 going to transfer energy through heat 00:01:34.06900:01:34.079 more readily than things like wood or 00:01:36.28900:01:36.299 brick so let's look at this Paet 00:01:38.21000:01:38.220 simulation so I've got iron i've got 00:01:40.58000:01:40.590 brick and then i've got water and so we 00:01:43.19000:01:43.200 can assume that we have the same amount 00:01:44.84000:01:44.850 of each of these and if i were to put 00:01:46.67000:01:46.680 the water on top of a heating device and 00:01:49.42900:01:49.439 the iron on top of a heating device and 00:01:51.31900:01:51.329 I were to just increase the amount of of 00:01:52.99000:01:53.000 energy what I'm going to see is an 00:01:55.39900:01:55.409 increase in temperature well what's 00:01:56.74900:01:56.759 really going on is that we're speeding 00:01:58.55000:01:58.560 up those molecules that's speeding up 00:02:00.23000:02:00.240 the molecules of the thermometer it's 00:02:01.70000:02:01.710 spreading a power likewise when we cool 00:02:03.67900:02:03.689 it down what we're doing is we're 00:02:05.53900:02:05.549 cooling down those molecules cooling 00:02:07.49000:02:07.500 down the molecules of the thermometer 00:02:09.05000:02:09.060 and therefore it's going down but we 00:02:11.30000:02:11.310 really don't see that energy transfer is 00:02:13.25000:02:13.260 he 00:02:13.60000:02:13.610 and so now what we're going to do is 00:02:15.04000:02:15.050 we're going to click on the energy 00:02:16.33000:02:16.340 symbols button and now we're actually 00:02:18.37000:02:18.380 going to see that energy inside those 00:02:20.41000:02:20.420 molecules now as I'm heating it up 00:02:22.33000:02:22.340 what's really happening is I'm adding 00:02:24.37000:02:24.380 energy I'm adding energy to that iron 00:02:27.01000:02:27.020 now you can see that some of it is being 00:02:28.84000:02:28.850 transferred out to the environment 00:02:30.46000:02:30.470 through heat 00:02:31.09000:02:31.100 likewise when I cool it down what I'm 00:02:33.16000:02:33.170 doing is I'm actually transferring that 00:02:34.87000:02:34.880 energy as heat into the ice cubes so 00:02:36.94000:02:36.950 there have lower kinetic energy what 00:02:39.61000:02:39.620 happens if I take that iron and I just 00:02:41.20000:02:41.210 throw it into the water you can see that 00:02:42.85000:02:42.860 since it's hotter it's transferring some 00:02:44.68000:02:44.690 of that energy as heat as well to the 00:02:46.96000:02:46.970 surroundings until it eventually reaches 00:02:48.79000:02:48.800 what we call equilibrium and so if you 00:02:51.31000:02:51.320 ever have a warmer and a colder body 00:02:53.23000:02:53.240 that warmer body is going to have a 00:02:55.00000:02:55.010 higher amount of average kinetic energy 00:02:57.01000:02:57.020 and remember the Maxwell Boltzmann 00:02:58.44900:02:58.459 distribution shows us how that works if 00:03:00.94000:03:00.950 we were to look at it this would be the 00:03:02.05000:03:02.060 cold body and this would be the warm 00:03:03.69900:03:03.709 body now in each of those bodies they're 00:03:05.41000:03:05.420 going to have low energy particles and 00:03:07.63000:03:07.640 really high energy particles but in the 00:03:09.52000:03:09.530 warmer body that average kinetic energy 00:03:11.65000:03:11.660 is going to be greater and so if we ever 00:03:13.69000:03:13.700 put them in contact with another there's 00:03:15.69900:03:15.709 going to be a lot of collisions between 00:03:17.29000:03:17.300 these molecules and as they collide 00:03:19.00000:03:19.010 they're transferring some of that 00:03:20.50000:03:20.510 kinetic energy and so what we're really 00:03:22.33000:03:22.340 doing is we're transferring energy from 00:03:24.19000:03:24.200 the warmer object to the colder object 00:03:25.99000:03:26.000 through heat until they eventually reach 00:03:28.60000:03:28.610 what we call thermal equilibrium in 00:03:30.85000:03:30.860 other words it's the same average 00:03:31.99000:03:32.000 kinetic energy on both sides and that 00:03:34.18000:03:34.190 picture I showed you of iron at the 00:03:35.56000:03:35.570 beginning eventually what's going to 00:03:37.15000:03:37.160 happen is all of that iron is going to 00:03:38.94900:03:38.959 have the same amount of kinetic energy 00:03:40.96000:03:40.970 because we've transferred that energy 00:03:42.72900:03:42.739 out now it's not the same for every 00:03:44.74000:03:44.750 substance and so we use a term called 00:03:47.41000:03:47.420 specific heat capacity to measure that 00:03:49.30000:03:49.310 and so right here you could imagine we 00:03:51.13000:03:51.140 have a kilogram of gold a kilogram of 00:03:53.71000:03:53.720 aluminum and a kilogram of water and 00:03:56.32000:03:56.330 let's say that they're all in a 00:03:58.36000:03:58.370 container and so if you look at it 00:04:00.25000:04:00.260 they're going to have different amounts 00:04:01.36000:04:01.370 of specific heat capacity if we look at 00:04:03.28000:04:03.290 the units that's joules which is a way 00:04:05.25900:04:05.269 that we measure energy per gram and then 00:04:07.78000:04:07.790 Kelvin or degree Kelvin and so if you 00:04:10.18000:04:10.190 have something that has low specific 00:04:12.07000:04:12.080 heat capacity that means it's going to 00:04:13.78000:04:13.790 be chained the amount of energy it has 00:04:15.94000:04:15.950 is going to change more readily than 00:04:17.40900:04:17.419 something that has a higher heat 00:04:19.14000:04:19.150 specific heat capacity so let's add a 00:04:21.72900:04:21.739 little bit of heat to this and watch 00:04:23.23000:04:23.240 what happens to the thermometers 00:04:25.35000:04:25.360 and so the goal the aluminum are heating 00:04:28.17000:04:28.180 up more readily than the water now the 00:04:30.45000:04:30.460 energy is going to be the same it's just 00:04:32.70000:04:32.710 that the water has a higher specific 00:04:33.86900:04:33.879 heat capacity and so it's able to absorb 00:04:36.83900:04:36.849 more energy before it starts to change 00:04:38.67000:04:38.680 its temperature and so did you learn to 00:04:41.18900:04:41.199 explain how heat exchange is due to 00:04:43.11000:04:43.120 kinetic energy transfer due to molecular 00:04:45.42000:04:45.430 motions if you did you learned what I 00:04:48.27000:04:48.280 wanted you to and I hope that was 00:04:49.58900:04:49.599 helpful
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