Temperature: Videos & Practice Problems

Understanding the concepts of temperature and heat is essential in the study of thermal energy. Temperature is the average kinetic energy of molecules within a substance and is measured in degrees Celsius, Fahrenheit, or Kelvin. It is an intensive property, meaning it does not depend on the amount of substance present. Heat, in contrast, is the transfer of thermal energy from a warmer object to a cooler one and is an extensive property, meaning it varies with the amount of substance. To accurately convert between temperature scales, two key formulas are necessary:

$K=\mathrm{°C}+273.15$

and

$\mathrm{°F}=1.8\times \mathrm{°C}+32$

These conversions are crucial for precise scientific measurements and should be committed to memory for practical application in experiments and calculations.

Temperature vs Heat

Now, the words temperature and heat are often used interchangeably with one another, but they're not the same thing. They represent different aspects of thermal energy. Now thermal energy itself is the sum of all kinetic and potential energies of all atoms in an object. Now when we say kinetic energy, we know that kinetic energy is the energy of motion. So the movement of molecules, the movement of atoms, potential energy is just the energy of position. Were those molecules are related? Are they 100 feet off the ground? Are they 10 feet off the ground? Where exactly are they located?

Now temperature and heat again are used interchangeably with one another, but they're not the same thing. Temperature itself is the average kinetic energy of an object that is a measurement of thermal energy. Remember that temperature itself is an intensive property. It is the inside or innate properties of a substance that is independent on the amount of that substance. For example, if we have a cup of water that's 100°C versus a gallon of water that's 100°C. The amount of water is different, but the temperature is the same. Because the temperature is the waters are at at the moment. Doesn't matter how much of the water we have. OK, so temperature is an intensive property.

Heat, on the other hand, is not. Heat is the flow of thermal energy from an object at a higher temperature to an object at a lower temperature. So it's normal for heat to move from a hotter object to a colder object. If you have a hotter object next to a colder object, eventually all the heat from the hotter object moves towards the colder one. So to heat it up, Heat itself is based on the amount of the substance present, so it would represent an extensive property. Now knowing the difference between temperature and heat is critical.

For the example that's left right below it. If we take a look at this example question, it says from the image provided below, determine which part of the cubes represent temperature and which part represents heat. All right, so we have two cubes here. We can see that the cube on the left has those little red balls that seem to be bouncing everywhere. They're highly energetic. That happens because the overall temperature in this cube is higher. So we'd say that this cube has a higher temperature. Then if we look on the other side, we see that they are kind of like stuck in place. They're not moving at the same speed as before. That's because they are at a lower temperature.

And remember we just said that heat goes from a higher temperature to a lower temperature object. That is explained by these WAVY lines. So here we see that heat is leaving the left cube and going to the right cube. So these WAVY lines represent heat. So that's how you need to understand temperature is an actual measurement. 100° twenty degrees 98°F. These are actual numbers. Heat is just a flow of thermal energy from a hotter object to a colder object. Although they're used interchangeably, sometimes they are not the same thing.

Now that we've talked about the difference between intensive when it comes to temperature and extensive when it comes to heat, let's move on to our next practice question.

Heat vs Temperature Example

Hey everyone so here in this example question it says from the image provided below, determine which part of the cubes represent temperature and which part represents heat. So remember heat itself just represents the flow of thermal energy from an object that's hotter to an object that's colder.

If we take a look here we have these two cubes and we can see that we have a set of WAVY lines between them. These set of WAVY lines themselves represent our heat. Temperature itself is a result of the movement of molecules within a given structure. So if we take a look here, we can see that in the first cube, let's call it cube one, we can see that we have these little balls that are moving around. And in the second cube, cube two, we have the same balls, but they're not moving as vigorously.

We're going to say here temperature is really just the movement in each cube. So you could say that temperature is represented by the molecules moving in this cube as well as in this cube. Remember we said that heat is the flow of energy from a hotter optic to a colder object. The objects in the first cube, we can see them moving more vigorously, more more actively. Therefore they would generate higher temperature.

So we'd say that cube one would have a higher temperature. And the balls in the second cube are moving slower, so they have a lower temperature. This reinforces the idea that heat, which we said are these WAVY lines, would go from cube one to cube 2. They're going from a higher temperature to a lower temperature, so keep this in mind when learning the distinction between heat and temperature.

Which of the following containers would have the greatest flow of thermal energy in the form of heat?

• A.
• B.
• C.

Answer: (B)

Temperature Conversion Formulas

Now, temperature can be measured in units of Celsius, Fahrenheit and Kelvin. And when it comes to these temperature units, we can convert between them. In order to convert between them, we just have to utilize certain formulas. Now here we have purple boxes. And when we have these purple boxes, that means that that's a term or formula you have to memorize. OK, you have to commit it to memory because oftentimes it's not given to you on an exam or a quiz.

Now the first one connects Kelvin to degree Celsius, and it's that Kelvin equals degree Celsius plus 273.15. Oftentimes professors will drop the .15 part, but to be as accurate as possible, it's important that you use the whole number, so 273.15. From this equation we can see that Kelvin directly connects to degrees Celsius and we can go between them.

The next equation connects degrees Fahrenheit to degrees Celsius and the equation is degrees Fahrenheit equals 1.8 times degree Celsius plus 32. So this formula here shows us that degree Celsius is connected to degrees Fahrenheit. So from these 3 units we can see that Celsius is in the middle. So Celsius acts as the bridge that connects Kelvin to degrees Fahrenheit.

So just remember, when it comes to temperature, we have 3 units that we can use. And when it comes to changing between them, these are the two formulas you need to commit to memory. Anytime you see a purple box, remember that means you're going to have to memorize either that term, that definition, or in this case, a formula.

K = °C + 273.15 °F = 1.8 × °C + 32

Temperature Conversion Example

Let's take a look at the following example question here. It says one of the hottest recorded days in the country was 128°F in Lake Havasu City, AZ. If the melting point of phosphorus is 44.15°C, would it exist as a solid or liquid on this extremely hot day?

All right, so we see that in the question we're dealing with units of Fahrenheit and Celsius. From the equations up above, we know what's the second one we're going to have to use in some way. So we have degrees Fahrenheit equals 1.8 times degrees Celsius plus 32. They're giving me the temperature in Lake Havasu in Fahrenheit, but I mean I need to compare it to this melting point of phosphorus which is in Celsius.

If the temperature I find is equal to or greater than 44.15°C, that means that phosphorus will melt and it will be in its liquid form. If the temperature on this extremely hot day is not at least 44.15°C, then it won't be hot enough and phosphorus will not melt and remain a solid. So I'm going to plug in what I have for Fahrenheit, which is 128 and this is 1.8°C + 32.

Subtract 32 from both sides. So when we do that we get 96 = 1.8 times degrees Celsius. Divide both sides now by 1.8 and now we'll have the temperature in Lake Havasu in degrees Celsius. So our degree Celsius here equals 53.3. Now we needed the temperature to be at least 44.15°C per phosphorus to melt. This answer is much greater than it, so yes, it's hot enough for phosphorus to melt, therefore it'll exist in its liquid form.

Now that we've seen this example on how to relate Fahrenheit to degree Celsius, move on to the next video and let's take a look at the practice question.

At what temperature is the temperature in degrees Fahrenheit equal to the temperature in degrees Celsius?

• A. 0º
• B. 25º
• C. -40º
• D. -29º

Answer: (C)

Here’s what students ask on this topic:

What is temperature?

Temperature is a measure of the average kinetic energy of the particles in a substance, such as atoms or molecules. It's an indicator of how hot or cold an object is and can be measured using various scales, including Celsius (°C), Fahrenheit (°F), and Kelvin (K). The higher the temperature of a substance, the faster its particles are moving. In the context of physics, temperature is a fundamental parameter that affects the state of matter (solid, liquid, gas, or plasma), the rate of chemical reactions, and the emission of radiation. It's also a critical factor in the study of thermodynamics, which is the science of heat, work, and the flow of energy. Temperature measurements are essential in a wide range of applications, from daily weather forecasts to the management of industrial processes and the study of cosmological phenomena.

How to convert degrees Celsius to Fahrenheit?

To convert degrees Celsius to Fahrenheit, you can use the following formula:

°F = ( °C × 9 5 ) + 32

Here's how you do it step by step:

1. Take your Celsius temperature and multiply it by 9/5 (or 1.8).
2. Add 32 to this number.

For example, if you're converting 25°C to Fahrenheit:

1. 25 × 9/5 = 45
2. 45 + 32 = 77

So, 25°C is equal to 77°F.

Remember, the "°" symbol represents degrees, "C" stands for Celsius, and "F" stands for Fahrenheit. This formula is a linear conversion, meaning it can be used to convert any Celsius temperature into Fahrenheit.

How do you convert Celsius to Kelvin?

Converting Celsius to Kelvin is a straightforward process. The Kelvin temperature scale is an absolute scale where 0 Kelvin is absolute zero, the point at which particles theoretically stop moving. To convert a temperature from Celsius to Kelvin, you simply add 273.15 to the Celsius temperature. This is because the size of one degree Celsius is equal to the size of one Kelvin, but their starting points are different. The Kelvin scale starts at absolute zero, whereas the Celsius scale sets its zero point at the freezing point of water.

Here's the conversion formula:

K = °C + 273.15

For example, if you have a temperature of 25°C and you want to convert it to Kelvin:

K = 25 °C + 273.15 = 298.15 K

So, 25 degrees Celsius is equal to 298.15 Kelvin. Remember that Kelvin does not use the degree symbol; it's simply written as 'K'.

How do you convert Fahrenheit to Kelvin?

To convert a temperature from Fahrenheit to Kelvin, you'll need to follow a two-step process. First, you convert Fahrenheit to Celsius, and then you convert Celsius to Kelvin. Here's how you do it:

1. Start by subtracting 32 from the Fahrenheit temperature.
2. Multiply this number by 5/9 to convert to Celsius.
3. Finally, add 273.15 to the Celsius temperature to convert to Kelvin.

The formula looks like this:

K = ( F - 32 ) × 5 9 + 273.15

Where K is the temperature in Kelvin and F is the temperature in Fahrenheit.

For example, if you're starting with 68 degrees Fahrenheit, you would do the following:

1. 68 - 32 = 36
2. 36 * 5/9 ≈ 20
3. 20 + 273.15 = 293.15

So, 68 degrees Fahrenheit is approximately 293.15 Kelvin.