During my chemistry and matter unit we discuss mixtures. We discuss heterogeneous and homogeneous mixtures. During this time I assign my students extra credit. I give them a copy of a chocolate chip cookie recipe and a peanut butter cookie recipe. We talk about what type of mixture each one is etc. The students are given extra credit if they make the cookies. They enjoy making the cookies and bringing them in to share with their friends. This makes learning more personal. It also helps them to understand that baking and cooking are chemistry in action. I give the students 10 points extra credit for each recipe. If they make the cookies but don't want to bring them in then they have a parent write a note that states they made the cookies.