Quiet now children!So before we begin, eyeson the board please.Study the illustration.
A thermometer is placed on the forehead of a kid with a fever. The thermometer reads 98 °F
The thermometer was not removed until the time reached 5 minutes. The thermometer now reads 101 °F 101 °F
Why did the Easy! Becausetemperature they’re not Bu..Bu..But..change after yet in thermal I, I can’tsome time? equilibrium! understand! Why?!
What!? Remember?When two substances havingdifferent temperatures areintroduced or kept together, heatflows from a substance at highertemperature to a substance atlower temperature.
To make it more correct, heat continues to be transferred until theirtemperatures are equalized. When this stage is achieved, only we can say that we can say that the substances are in thermal equilibrium.
Oohh.. So that explains why the liquidinside the thermometer rises as time passes by. Yes! That is why we need to wait for a few minutes before taking the reading of the thermometer.
Of course. With that, the kid’s body and the thermometer will reach the same temperatureHey! You keep on finishingmy sentences! Why are you late anyway? So what? I already understand the lesson.
You… you!!!!! Darn! You’ll pay for this!!!You’ll see! One day, I Whatever. will beat you!! Timmy. Holy!! My water is now getting warmer! Help me Timmy!!!
Don’t worry doggy, we’ll get Really?you some ice for you later Thanks But I wonder how many ice will make the juice cold again?
Timmy needs help… But it seems that you lost your magic powers....and equipped only with the knowledgeof thermal equilibrium. How are you going to help him?
First you need to Ti = 15 °Cconsider the condition m = 200 gof Doggy’s drink.How much ice wouldbe enough to cooldown the temperatureof the water? (mass) Tf = 10 °C
The mixture of ice and water wouldeventually reach thermal equilibrium. However, they must be in a closed system so that heat will completely transfer from one body to another.
Or simply, it must follow the Law of Conservation of Energy ΔE = 0No heat will flow out of the system