100 points! Please help! Will give brainliest!!

Imagine yourself making a nice cup of tea on a cold winter day. You begin by boiling some water in a kettle. Next, you add the steaming liquid to your cup. Then, you open a tea bag and repeatedly dunk it into the water. You pour a dash of milk and drop a few sugar cubes into the cup, stirring the solution with a spoon. Finally, you squeeze a bit of lemon into your tea mixture. However, before you have time to stir the lemon juice into your tea, the liquid forms clumps. In other words, your tea has curdled!

Based on the scenario, answer the questions below.

1. Which of the four indicators of a chemical change is described in the paragraph above?
2. What makes the tea with milk and lemon curdle?
3. Name some of the chemical substances in the tea mixture. (You will need to conduct some research on your own to do this.)
4. Which chemicals could have reacted to cause the curdling?