The idea of countable and uncountable nouns can be a difficult concept for students to grasp. Once they have understood the concept, it can take a long time to master and use correctly when speaking and writing.
Visual examples are useful for helping your students understand the distinction. Try to take some food items into class. Show your students the items and as a whole class help them classify the items. They'll soon see the difference between coffee and carrot, for example. You can then explain or elicit the difference between mass (uncountable) and unit (countable).
If you think your students are up to it, you can show the distinction between a cucumber and cucumber (as chopped up for a salad). Similar examples include: tea / teabags and sugar / sugar cubes.
You can then draw 5 or 6 vertical lines on the board to represent units or countable items and a scribbled mass or criss cross of lines to represent mass or uncountable items. Students then organise the food items you have just studied into the categories. They can continue in pairs with pictures of other items or a list that you give them.
Explain the use of singular or plural verbs with countable and uncountable items. Depending on their level and the amount of challenge you think they are ready for, they can make sentences using a picture you give them and the following structures:
There's some ________ on the table
There isn't any ________ on the table
There are 5 ________ on the table
There aren't any ________ on the table
Are there any ________ on the table?
Yes, there are / No, there aren't.
Is there any ________ on the table?
Yes, there is / No, there isn't.
How much ________ is there? There's a lot / there isn't much.
How many ________ are there? There are a lot / there aren't many.
Try to incorporate both written and spoken work and follow up with more work in the next class.