There are not any high school level gas law problems that the ChemTeam is aware of that use the Celsius temperature directly in the calculation.
If you have a Celsius temperature in the problem, you MUST change it to Kelvin, in order to use it in your problem.
Sometimes your teacher might put a temperature in the problem, but you really don't need to use it. Your teacher is doing what he or she is driven to do: trying the confuse poor teenage kids who are really trying their hardest. The ChemTeam understands this fully for, you see, this is what happens in his class. All teachers know this is really fun! OK, back to work.
You can convert bewteen Celsius and Kelvin like this: Kelvin = Celsius + 273.15. Often, the value of 273 is used instead of 273.15. Check with your teacher on this point. All examples to follow will use 273.
A point before going on to some problems: very often in gas law problems it looks like significant figure rules are being violated. The reality is that they are not. In reality, the significant figure concept is more complex than the simple rules taught at this level.
However, having said that, be careful to watch your teacher's actions in class and ask what the rules are in your class. Don't use this phrase" "Well, there's some guy on the Internet who says you're wrong."
Example #1: convert 25.0°C to Kelvin.
Answer: 25.0 + 273 = 298.0
Essentially the 273 is being treated as 273.0
Everybody (except you!) in chemistry knows the true conversion value is 273.15, but the decimal portion is usually ignored. Also, the most common type of thermometer in high school labs is readable to the nearest tenth. So temperatures are usually written just to the tenth place at this introductory level
The ChemTeam occasionally has a student who insists on using 273.15. You may be the same. However, be careful on this. You may do a test calculation using 273.15 and the teacher does it with 273. That difference may generate a value for your answer that causes the teacher to deduct points. Follow the policy your classroom teacher sets down.
Example #2: convert 375 K to degrees Celsius.
Answer: 375 - 273 = 102°C
Example #3: Convert - 50°C to Kelvin.
Answer: - 50 plus 273 = 223 K
The ChemTeam doesn't feel any extra practice problems are needed. See your classroom teacher if you need more.