First, you need to buy all the ingredients (List shown in powerpoint)
Once you get the ingredients, you'll have to follow the instructions
Step one: Pre heat oven at 180 degrees C. Oil one large or two medium baking tins.
The physical changes to this are preheating the oven as it is physically increasing in size. In addition to this, there is also oiling the trays as you are physically putting the oil on the tray, there is no substances being changed so there is no chemical changes.
Step Two: Sieve flour and cocoa into a bowl and stir in sugar. Add eggs, milk and, oil. Mix well together with electric mixer.