This is one of my favorite themes to do with preschools. I have tweaked some of my favorite activities so they can be done with emergent (and beyond) readers/writers.
Smell - Number film canisters and poke a hole in the lid. Put in a cotton ball soaked or coated in various liquids and powders such as perfume, lemon juice, cocoa powder, baby powder, peanut oil (or butter), suntan lotion (for coconut), vanilla extract, almond extract, mint extract or oil, rose water, cinnamon powder, orange oil…
Have slips with the different scents written on them and have the students fill out the slips to see if they can detect the smells.
Vision - Display some optical illusions or directions for making the “sausage finger”. Also try some residual color pictures (where after looking at them and then a white surface, you see the opposite color) and stereograms. Think about including some samples of tests to determine color blindness. A pair of 3-D glasses and 3-D pictures…
Hearing - have a fill-in test where students can figure out the hearing range some animals have (bats, whales, and elephants have some extreme ranges). Tie a tuning fork and a surface for the students to tap it on and observe how the sound can change as you move it closer and farther away from you ear. Burn a CD of 10-20 sound effects (some downloadable SFX can be easily found on websites) and have the students write the sound they hear. Have paper tubes, such as a toilet paper tube, a foil wrap tube, and a paper towel tube (I was lucky enough to get a 5-foot long contact paper tube when I taught simple physics last summer), and compare each tube to discover how the ability to hear sound improves as the tube gets longer.
Touch - Put different grades of sandpaper into empty tissue boxes. Have the students put the boxes in order of roughest to smoothest based on what they feel inside the box. Have a feel bag with different kinds of paper (wax paper, wrapping paper, the sticky part of a post-it note, sandpaper, corrugated cardboard, wallpaper samples, etc.) where the students have to determine the texture (smooth, rough, slippery, sticky, bumpy, etc.) before pulling the paper out to check their answer. Cut out letters from sandpaper and glue words inside a tissue box with the top cut off. Without looking, have the students write down the letters they feel. They can check to see if they got the right word by turning the box around.
Not sure how to do a taste display where the children are working independently and besides…as I tell my kids, “If I gave you the answers now, I’d have to follow you around for the rest of your lives and tell you all the answers.”