Grade 11: Thermodynamics 🔥❄️

Interactive Lesson • $\text{Heat}$ $\text{vs.}$ $\text{Temp}$ • $\text{Laws}$ of $\text{Thermodynamics}$ • $Q = mc\Delta T$

Heat $\text{vs.}$ $\text{Temperature}$ 🌡️

  **$\text{Thermodynamics}$** is the branch of $\text{physics}$ that deals with $\text{heat}$ and its relation to $\text{work}$ and $\text{energy}$.

 
   

$\text{Heat}$ ($Q$)

   

**$\text{Energy}$ $\text{in}$ $\text{transit}$** ($\text{flow}$) due to a $\text{temperature}$ $\text{difference}$. Heat always $\text{flows}$ from $\text{hot}$ to $\text{cold}$.

   

$\text{Unit}$: $\text{Joule}$ ($\text{J}$).

 
 
   

$\text{Temperature}$ ($T$)

   

A measure of the **$\text{average}$ $\text{kinetic}$ $\text{energy}$** of the $\text{molecules}$ in a substance.

   

$\text{Unit}$: $\text{Kelvin}$ ($\text{K}$) or $\text{Celsius}$ ($^{\circ}\text{C}$).

 
 
   

$\text{Internal}$ $\text{Energy}$ ($U$)

   

The $\text{total}$ $\text{energy}$ contained within a $\text{thermodynamic}$ $\text{system}$. $\text{Related}$ to both $\text{potential}$ $\text{and}$ $\text{kinetic}$ $\text{energy}$ of the $\text{molecules}$.

 
 
Score: 0
 
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The $\text{Laws}$ $\text{of}$ $\text{Thermodynamics}$ 🛑

 
   

$\text{Zeroth}$ $\text{Law}$ ($\text{Equilibrium}$)

   

If two $\text{systems}$ are each in $\text{thermal}$ $\text{equilibrium}$ with a third $\text{system}$, then they are in $\text{thermal}$ $\text{equilibrium}$ with each $\text{other}$.

   

$\text{Key}$: Defines $\text{temperature}$ and ensures $\text{thermometers}$ work.

 
 
   

$\text{First}$ $\text{Law}$ ($\text{Conservation}$ $\text{of}$ $\text{Energy}$)

   

The $\text{change}$ in $\text{internal}$ $\text{energy}$ ($\Delta U$) of a $\text{system}$ is $\text{equal}$ to the $\text{heat}$ $\text{added}$ to the $\text{system}$ ($Q$) $\text{minus}$ the $\text{work}$ $\text{done}$ by the $\text{system}$ ($W$).

    $$\Delta U = Q - W$$  
 
   

$\text{Second}$ $\text{Law}$ ($\text{Entropy}$)

   

The $\text{total}$ $\text{entropy}$ (disorder/randomness) of an $\text{isolated}$ $\text{system}$ can $\text{only}$ $\text{increase}$ over $\text{time}$.

   

$\text{Key}$: $\text{Heat}$ $\text{cannot}$ $\text{spontaneously}$ $\text{flow}$ from $\text{cold}$ to $\text{hot}$.

 

Specific $\text{Heat}$ $\text{Capacity}$ 🧊

  **$\text{Specific}$ $\text{Heat}$ $\text{Capacity}$ ($c$)** is the amount of $\text{heat}$ $\text{energy}$ required to $\text{raise}$ the $\text{temperature}$ of $\mathbf{1 \text{ kg}}$ of a $\text{substance}$ by $\mathbf{1 \text{ K}}$ (or $\mathbf{1^{\circ}\text{C}}$).

   

$\text{Specific}$ $\text{Heat}$ $\text{Equation}$

   

The heat energy ($Q$) required for a temperature change ($\Delta T$) is calculated by:

    $$Q = mc\Delta T$$    

where $m$ is $\text{mass}$ ($\text{kg}$), $c$ is $\text{specific}$ $\text{heat}$ $\text{capacity}$ ($\text{J}/(\text{kg}\cdot\text{K})$), and $\Delta T$ is the $\text{change}$ in $\text{temperature}$ ($\text{K}$ or $^{\circ}\text{C}$).

Interactive $\text{Specific}$ $\text{Heat}$ $\text{Calculation}$ 🧮

Use the $\text{Specific}$ $\text{Heat}$ $\text{Equation}$ ($Q=mc\Delta T$) to calculate $\text{Heat}$ $\text{Energy}$.

   

Problem:

   

How much $\text{heat}$ $\text{energy}$ ($Q$) is needed to $\text{raise}$ the $\text{temperature}$ of $2.0 \text{ kg}$ of $\text{water}$ by $10^{\circ}\text{C}$?

   

($\text{Specific}$ $\text{heat}$ of $\text{water}$ is $\mathbf{4180 \text{ J}/(\text{kg}\cdot^{\circ}\text{C})}$)

   

$$\text{Calculation}: Q = (2.0 \text{ kg}) \times (4180 \text{ J}/(\text{kg}\cdot^{\circ}\text{C})) \times (10^{\circ}\text{C}) = ? \text{ J}$$

   
                $\text{J}$            
   

⚡ $\text{Thermodynamics}$ $\text{Law}$ $\text{Check}$!

Identify which of the $\text{Laws}$ best explains the following scenario.

 
A $\text{perpetual}$ $\text{motion}$ $\text{machine}$ that creates $\text{energy}$ out of $\text{nothing}$ is $\text{impossible}$.
 
     
 
 

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