00:02 Good day, everyone.

00:12 My name is Tabelo A.A.

00:14 A Physician for today.

00:15 The topic for discussion today is heat energy.

00:20 Lesson of objectives.

00:24 At the end of the lesson,

00:25 the students should be able to

00:26 one, define heat and temperature,

00:30 two, state differences between heat and temperature,

00:35 three, state three effects of heat and a substance,

00:39 four, give kinetic theory explanation

00:42 or movement of atoms or molecules

00:45 and solid, liquid, and gas.

00:48 Lastly, briefly explain thermal expansivity.

00:55 Heat energy.

00:56 Heat energy is a result of movement of tiny particles

01:00 called atoms, molecules, or ion in solid, liquid, and gas.

01:05 Heat energy can be transferred from one object

01:09 to another in the form of heat.

01:12 It is a scalar quantity.

01:14 Its unit is dual and it is measured

01:17 with instruments called caloriminter.

01:20 Temperature is the degree of hotness

01:23 or coldness of the body.

01:25 It determines the direction of flow of heat.

01:29 The unit of measurement temperature is Kevin

01:35 and the instruments we use to measure temperature

01:38 is thermometer.

01:39 Now, differences between heat and temperature.

01:45 In terms of definition,

01:49 heat is a form of energy.

01:52 White temperature is a measure of the degree of hotness

01:55 or coldness of the body.

01:57 In terms of units, heat is measured in dual or calorie.

02:04 White temperature can be measured in sessions,

02:08 Kevin or Fahrenheit.

02:10 Values, heat is always positive in value,

02:16 but temperature can be positive or negative.

02:20 Now, property.

02:21 Heat can go from hot to cold,

02:26 but temperature rises when heated

02:29 and fall when cold.

02:32 Heat is also measured with caloriminter.

02:35 White temperature is measured with thermometer.

02:39 The total kinetic energy and potential energy

02:42 obtained by molecules of an object, that's also of heat.

02:46 White temperature is every kinetic energy of molecules

02:50 in the substance.

02:51 The symbols, heat is always represented by symbol H,

02:56 while our temperature is only represented by symbol C.

03:02 Also, rise in temperature.

03:06 Where substances are subjected to heat,

03:09 there's always change and increase in the temperature of the body.

03:14 Likewise, one of the effects is change of states.

03:20 Where substances are heated?

03:21 It's either they change from solid to liquid or from liquid to gas.

03:27 Take, for example, an ice block.

03:30 It's always a solid.

03:33 But when it is subjected to heat,

03:36 after some time, the solid block turns to liquid, which is water.

03:41 And that water, if it is subjected to heat again,

03:45 when water starts boiling,

03:48 it's produced vapor or steam.

03:50 In other words, the steam of vapor is also a gas.

03:55 So, for that example, we discover that the states are changing.

04:00 From solid, when it is ice,

04:02 to liquid, when it is water, and to vapor, when it is gas or steam.

04:08 Then, one other effect of heat is there is always change,

04:12 or changes in physical properties.

04:15 Where substances are subjected to heat.

04:18 Also, there is chemical change.

04:21 When those substances are equally subjected to heat,

04:26 and at the same time, there is also called tammionic emission.

04:29 That is given out of electrons as a result of some atom or elements

04:36 being subjected to heat.

04:38 Now, let's see the characteristics of atoms and solid.

04:44 For solid, the atoms or molecules are fixed and devibrates

04:49 about their main position.

04:50 The molecules are tightly packed together.

04:54 That's why they have their ship.

04:57 They are very strong attractive force,

05:01 existing between the molecules and solid.

05:04 They have definite ship.

05:06 They are in fixed position, but at the same time,

05:10 they can change phases. That is, when they are solid,

05:14 to subject them to heat, you can weaken their structure

05:18 where they become liquid.

05:20 Now, liquids.

05:23 Liquid also consists of atoms or molecules.

05:26 And their particles, they have more energy and solid.

05:30 There are no space between them, not all like solid.

05:33 Where there is no space, they only vibrate about their main position.

05:37 But for liquid, they have more energy.

05:40 There is no space, so they can move around.

05:42 And the particles, they also vibrate about their position.

05:45 The intermolecular forces of attraction between

05:49 liquid is weaker compared to that of solid.

05:54 And as far as liquid is concerned, they can also change phases.

06:00 That is, they can move from liquid to gas.

06:03 Now, gas.

06:08 They also consist of atoms or molecules.

06:11 They possess high energy.

06:14 And they are always in constant motion.

06:18 They occupy larger spaces than solid and liquid.

06:23 So they are free to move around.

06:25 And the force of attraction between them is weaker.

06:29 Compared to the last space between them.

06:32 And that force is weaker compared to that of liquid.

06:38 And that of solid.

06:39 And also, they can be cooled to change phases.

06:44 That is, the gas can be reverted to liquid.

06:49 Why the liquid can also revert to solid.

06:52 And in doing this, you have to remove heat from them.

06:55 Now, kinetic theory explanation of temperature.

07:00 Where substances are subjected to heat.

07:05 There is always an increase in temperature.

07:08 And this increase in temperature leads to the increase in the average kinetic energy of the molecules.

07:16 The pressure of a container is determined by the number of times gas molecules strikes the container.

07:23 That is, as much as the molecules acquire enough energy,

07:27 the movie about hitting the wall of the container and as a result of that generates pressure.

07:35 The particles speed increase due to heat absorbed.

07:38 And there is also an increase in kinetic energy of the molecules leading to increase in temperature of the substances.

07:47 Now, tamar expansivity.

07:51 Tamar expansivity or tamar expansion is the tendency of matter to change its shape.

08:00 Earlier, volume and density in response to change in temperature.

08:06 In other words, when substances are subjected to heat,

08:11 there is every tendency for those substances to change their shape.

08:17 They are area, they are volume and density as a result of heat, the suffer or the experience.

08:26 And depending on the type, tamar expansion is divided into three.

08:31 We have what we call linear expansion.

08:34 That is an increase in length, where substances are subjected to heat.

08:39 Then, earlier expansion, increasing length and breadth.

08:43 And we talk about volume expansion.

08:47 That is increasing length, breadth and height.

08:51 Examples of tamar expansion are stock lid of a glass jar.

08:59 Normally, when we have a glass jar with a lid cover and it is always very difficult for us to open it,

09:06 when that lid is subjected to heat, we can heat it a little bit.

09:11 When we do that, there is a little expansion and as a result of that,

09:15 we can easily remove the lid cover without breaking the bottle.

09:20 Then, one other example of tamar expansion are when we look at our various bridges.

09:28 There are always joints where the bridges are divided by meters along the road.

09:35 That is why when we are driving, when the tyrant will get to that point,

09:40 you see the tyrant shouting, boom, boom.

09:43 Those joints are not there for decoration.

09:46 They are there because number one, the road is made up of cota.

09:51 Very dark and for every dark substance, they are very good absorber of heat.

09:56 As a result of that, the cota, they absorb heat from the sun.

10:00 When we do that, the road is burnt.

10:02 When the road is burnt, the metal that is used in dividing the road creates room for expansion.

10:10 So that by the time they are burnt, there will be no bubbling of the road.

10:15 And by the time there is no more sun, when the sunlight is set, when the sun is set,

10:20 there is always the temperature will cool.

10:23 There will be lots of heat to the surrounding.

10:26 And when that occurs, the road will contract again.

10:30 So there is that metal used in dividing road and bridges only creates room for expansion.

10:38 So that the road doesn't bubble and doesn't get spoiled.

10:43 Likewise, we talk of sagging of cables.

10:46 Generally, the cables used by the PSN for us to tap our lights or whatever,

10:53 they are made up of aluminum, they are made up.

10:56 And they are very good conductors of heat.

10:58 That is why when they are spreaded the road from one pole to the other,

11:04 they don't allow it to be taught to be too tight.

11:07 They will give room for it to slack.

11:10 And you see that when there is expansion, it will accommodate it.

11:14 And when there is contraction, it will go back to the original ship.

11:18 That is the essence of sagging of cables when they are being spread on the poles.

11:25 Then we want to call biometallic stripe.

11:28 The best or simplest example of biometallic stripe is our electric iron.

11:34 We know that by the time we plug our electric iron, we can see the lights.

11:40 If we bring out the lights, then after some time, the lights go soft.

11:43 That means within the iron, there is two on equal meter of the same length.

11:53 One will be iron and the other brass.

11:58 Now, when they are subjected to the same consistency of heat,

12:04 one expands better than the other.

12:08 In other words, if this is the contact point within the iron,

12:11 by the time it makes contact, it expands, it absorbs it and the meter will bend.

12:22 When it bends, it moves away from the contact.

12:28 That is when the lights and our iron will go off.

12:35 By the time light goes off, the meter starts loosening each, there will be contraction.

12:40 As it is loosening each, it is becoming stretched.

12:44 As it becomes stretched, it makes contact again.

12:47 By the time it makes contact again, you see the lights on and it will be hot.

12:51 That is why this device is called biometallic stripe or thermostat.

12:57 It is used to regulate the temperature of the body or system.

13:02 That is why it is called the most of the iron nowadays.

13:05 If you are to press a clutch, that is better for cutting.

13:09 It marks that you can easily adjust it to that particular point.

13:13 If it is sticky, there is a particular point to accommodate so that it doesn't burn our clutch.

13:19 To regulate the type of heat energy that will be supplied or electrical energy for us to press our iron.

13:27 That better biometallic stripe or thermostat

13:31 will also have it in our fridge, our refrigerator, our AC.

13:37 That's why it's called that when they are working for us.

13:39 So after some time, they will break as if they are not working.

13:42 Then after some time, you see them picking up again.

13:45 That is the essence of our biometallic stripe.

13:48 Then also, all the expansion of heat is that our car tire.

13:54 By the time you put air in them, air in the car tire gets warm after a long journey.

13:59 And this increases the pressure of the tire.

14:02 Then we can always move freely.

14:03 Likewise, railway lines.

14:06 For every railway line, the trucks, there is always a gap joined by metaplates.

14:13 Because still, the rail is made up of metas.

14:18 And those ones are very good absorbers of heat, they conduct heat a lot.

14:24 So by the time they absorb heat, they are always expansion.

14:28 Where allowances are not made, for those things, the rail buckle and easily it can cause accidents.

14:36 That's why at times, some train, they would drill.

14:41 So to avoid that, that's why it is always advisable that there are gaps between each of the rail.

14:49 And here we have a metaplate, journey them together.

14:54 That's the essence of our expansion, then at the same time, electric thermostats.

15:00 That's what we have in our refrigerator, fridge and some other instruments.

15:06 Now, linear expansion.

15:11 When substances are heated, there are expansion varies from one substance to another.

15:20 For solid, there is always an increase in length when heated, and this is what we call linear expansion.

15:28 The amount by which the solid expands depends on the following one.

15:34 The temperature, the higher the temperature, the greater the expansion.

15:39 That is, if the temperature is high, there's every room for the meta to increase in length.

15:49 Number two, initial length, the longer the length, the more the expansion.

15:55 And lastly, linear expansivity, the higher the linear expansivity, the faster the expansion.

16:02 In other words, the nature of the meta, or the solid, is taken into consideration.

16:08 That's why we discover that some meta, they become hotter, faster than each other.

16:16 Take, for example, aluminum and brass, when you subject the two to the same amount of temperature or heat,

16:23 the aluminum gets hotter, faster than our brass.

16:28 So, in that, that means we are talking about the nature, how they are commanded, heat, how they absorb,

16:35 and that is the linear expansivity.

16:38 Now, our definition for linear expansivity,

16:45 linear expansivity is always represented by the symbol alpha.

16:50 And it is defined as the increase in length per unit's length per degree rise in temperature.

16:58 If it is represented by the symbol alpha, we have increased in lengths

17:11 all over original length, multiplied by temperature rise.

17:21 Now, if, by the time we are hitting, the substance,

17:38 if L1 happened to be the original initial length of the road at temperature theta 1,

17:48 which is noted, by the time it is heated, after some time, the length will increase,

17:55 and that will take place at the new temperature.

18:00 The new length, L2, and the new temperature, as theta 2.

18:09 Then, with this, we cannot talk about increase in length.

18:13 If we trade this down, we discover that from here to here is our increase in length.

18:26 So, coming back to the formula, linear expansivity was increase in length or change in length,

18:45 all over original length, multiplied by temperature rise.

18:58 Our increase in length will be L2 minus L1, all over L1, multiplied by theta 2 minus theta 1.

19:15 Just like what we have on the body here, our L1 is the original initial length,

19:20 L2, new length, theta 1, initial temperature, and theta 2, our final temperature.

19:29 From the formula, our L2 minus L1, which is equal to change in length,

19:40 will not be equal to linear expansivity, multiplied by original length,

19:48 multiplied by change in temperature, which is equal to theta 2 minus theta 1.

19:59 Therefore, the new length, the new length, which is L2, is not equal to L1 plus linear expansivity,

20:16 multiplied by original length, and brackets multiplied by change in temperature.

20:26 So, with this, we can easily solve problems associated with linear expansivity.

20:35 For example, the original length, L1, equals 10.0 meter, and L2 equals 10.50 meter.

20:53 Our theta 1 equals 30 degree, and theta 2 equals 80 degree.

21:07 Now, using our formula, linear expansivity equals L2 minus L1,

21:17 L1, multiplied by theta 2 minus theta 1, that is equal to 10.00 minus 10.50,

21:32 L1, 10.00, multiplied by 80 minus theta 3.

21:43 So, we have 0.50, L1, 10, multiplied by 50.

21:55 So, our linear expansivity for this material equals 1 times the rest of power minus 3 per kV.

22:07 That is the unit of linear expansivity.

22:11 Another example, we are still railway track, moving from kV to Funtua,

22:20 which is 2 already 50 kilometer long.

22:25 What is partial is produced when the temperature rises from 30 degree to 60 degree,

22:30 if the linear expansivity is still 0.001 per kV.

22:37 Now, our theta equals 30 degree, and our theta 2 equals 60 degree.

22:52 Why our initial length or distance cover is 250 kilometer,

22:59 which is the same thing as 2 already 50,000 meter.

23:04 Now, linear expansivity equals L2 minus L1, all over L1,

23:11 multiplied by theta 2 minus theta 1.

23:20 And that is equal to L2 minus L1 equals L1 multiplied by alpha,

23:31 multiplied by theta 2 minus theta 1.

23:35 Our L1 is 250,000 multiplied by the initial length,

23:45 which is, we have this 0.001, multiplied by 80, I mean 60, yeah.

24:02 1 1 multiplied by 60 minus 30.

24:08 So, this is a 0.001, multiplied by 250,000 multiplied by 30.

24:18 So, our change in length, as a result of that temperature difference is 82.5 meter.

24:27 Evaluation, at the end of the lesson, we are expected to answer the following questions.

24:33 1. Define heat to temperature.

24:39 State 3 difference between heat and temperature.

24:45 And lastly, state 3 in fact, of heat on substance.

24:51 Thank you for watching.

24:53 My name is Mr. Bello, AA Till next time.

25:03 [Music]