Heat Up and Boil

Heat Up

When you add heat to something to make it warmer, you heat it up. You can turn on the heat to heat up a room or you can put food on the stove or in the microwave to heat it up.
Ex: Tyrell came home from work fairly late, so he just took some leftover pizza from the fridge and heated it up in the microwave.
Ex: Nino said it was really cold in the basement and asked if he could bring a blow heater to heat it up a bit more. When you heat up some food that used to be hot but has since gotten cold, like leftovers or prepared frozen food, you reheat it.
When you heat something up in the microwave, you can also simply say that you are microwaving it.
Ex: We don't have a lot of food to cook with, but my mom said there are some leftover potatoes and chicken stew in the fridge that we can reheat.
Ex: My favorite snack is popcorn. It's good when you heat it up on the stove, but I like microwaving it because it's faster and easier.

Boil

When water reaches 100 degrees celsius and begins to bubble, it boils. When you cook food by putting it in boiling water, you also boil the food.
Ex: There is a pot of water on the stove and it's been there, on high heat, for about ten minutes. It is probably boiling by now.
Ex: My sister burned her hand pretty badly when she was boiling potatoes last night. As she was pouring the water through a strainer at the end, she spilled some on her hand and got a second-degree burn.
When it is very very hot, you can say that it is boiling. And if a person feels very hot he or she is boiling too.
Ex: Orla has asked if we could turn the air conditioning on because she is boiling. She thinks she might pass out if it doesn't cool down in here.
Ex: Florida is a beautiful place to visit in the spring, but by the summer it is just boiling and humid every day. It's not pleasant at all!