Yerin's POV

"The total pressure of a mixture of gases can be defined as the sum of the pressures of each gas: Ptotal = P1 + P2 + ... Pn. So Dalton's Law of Partial Pressure states that the partial pressure of an individual gas is equal to the total pressure multiplied by the mole fraction of that gas," I explained as I give examples to him regarding that topic. I noticed how his eyebrows met when he saw these bunch of word problems.

"Noona, can you elaborate it more? Seriously, my brain didn't function well today," Gyu pleaded while scratching his head.

"And how many times do I have to tell you that you should quit playing computer games? It distracts you from studying," I talked back and he just frowned. I tapped his shoulder and tried to encourage him more.

"Hey, you have the opportunity to study like this. Don't waste it. You're very lucky because your Mom sends you to prestigious school, you don't need to work just to help them, you're very lucky because you're still studying unlike me. You know what? I always think if when will I go to school again. Will I be able to see my friends again? Will I be able to pursue my dream? Hays, so don't miss this opportunity Gyu, okay?"

He just nodded and took the book that I'm holding.

"I'll try to understand it more. Can you elaborate more, noona?"

"Okay. Just a sec."

I took the pile of papers from my bag and put it in the table.

"So... remember that Boyle's Law and Ideal Gas Law tell us the total pressure of a mixture depends solely on the number of moles of gas, and not the kinds of molecules, right? But Dalton's Law allows us to calculate the total pressure in a system from each gas' individual contribution."

"Ah! I already got the one that you said earlier, the Ptotal = P1 + P2 +... Pn. The P1 and P2 are the partial pressure of gas 1 and gas 2 in the mixture," he exclaimed while pointing the formula on the book.

"Exactly! So can you solve this problem?" I gave him a piece of paper and he began reading it. After scrutinizing it, he smiled at me.

"The answer is 0.85 atm."

"Very well! Now try this.... A mixture of 2 mol H2 and 3 mol He exerts a total pressure of 3 atm. What is the partial pressure of He?"

He wrote on his note and probably he's solving this easy problem.

Minutes had passed but he still didn't get the answer so I asked him.

"Need help?"

"Tss, noona, can you tell the answer please? I really don't get the answer correctly," he complained and starting to feel annoyed. I barely smiled at him.

"The answer is 95 atm. Remember that in finding the partial pressure of the gas, you have to multiply the total pressure by the mole fraction of the gas. In this case, you have the 3 atm as the total pressure and the mole fraction of He is 3/5 so the answer is 95 atm."

"Aish! I forgot about that mole fraction!" He said while tapping his head.

"Easy, you'll master it soon. I'll help you don't worry," I assured him.

"Gomawo, noona! You really are a blessing!"

"Silly. Hahaha! It's nothing," I giggled as I ruffled his hair.

"Hmm... noona? I'll try to talk to Mom. I'll ask if she can make something to make you go back to school."

"No Gyu. Thank you for that but it's a no. It's enough for me that you treat me nicely and your Mom pay me well for tutoring you. It's really a big help for me. And don't worry, I'll be okay. I'll be going back to school soon," I smiled to him and he just pout so I pinched his cheeks.

"What's your dream, noona?"

"Me? I want to be a Chemist. How about you?"

"Chemical Engineer, you're my idol, noona. You're really good at Chem that's why I admire you." He beamed a smile and he winked at me. I squeeze his cheek for being cute.

When I finished tutoring him, I bid my goodbye to him and also to his Mom. He even gave me a chocolate cookies before I went out. How sweet...

"Thank you for today Yerin. Also, thank you for tutoring my son even though he's really stubborn and lazy," Gyu's Mom said while giving me the money.

"Mom! Don't talk like that infront of noona, it's embarassing!" Gyu retorted.

"Ahehe! Thank you as well, Aunt Miyu. And Gyu is not really stubborn at all. I can see that he's now determined to study well."

I looked at Gyu who's now smiling from ear to ear.

After that, I finally took the road on the way to our home. It's a walking distance from our home.

Aunt Miyu is a friend of Mom and offer me to tutor her son. I decided to take it to help my Mom in financial needs.

Ever since my father died in a car accident, we became immersed in debts. That's why I decided to stopped studying for a while and just help Mom in making and selling ricecakes. Good thing that I have an extra income for tutoring Gyu.

I missed my school friends. It's been one year already. I also missed going to school and listening to the lectures.

While walking, I shot a sideward glance to the coffee shop nearby but I suddenly stopped and stared there as I saw a familiar figure.

Now Playing: From Me by Gfriend



She's there while sipping her favorite iced coffee. She's smiling from ear to ear.

I missed her smiles.

Her smile that almost removed my vexation.

Her smile that will give you warmth despite of her cold aura.

I want to hug her tightly. I want to say those words again.

If I could go back in time, I should've fight my love for her.

I walked towards the coffee shop but to my surprise, I saw her with someone else.

She's already with Moonbin.