Simple lesson to review simple machines. It's tagged for 3rd - 5th grade, but could work for a quick review. It has a card sort activity ready to go. The agricultural examples might not be 100% relevant to all kids, but still useful.
Diffusion in a baggie- an alternative to the gummy bear lab. You will need cheap baggies, corn starch, and iodine. This can be done in one day, or split into two days.
Also, a link to the teacher's notes.
A visualization from NOAA that shows what the earth would look like if all water drained out. Good to show so students can see the mid-ocean ridges, ring of fire boundary, etc.
Use a two liter, three pencils, vinegar, baking soda, a paper towel, and a cork to build this rocket. Pretty simple! This experiment easily goes along with Newton's Laws, scientific inquiry, or chemical reactions.