The best professional development I ever participated in was Project Discovery, Ohio's mid-90s initiative to reform math and science education. The idea was to help students discover ideas, rather than to always feed them the conclusion first. A few years ago I saw Dan Meyer's Ted Talk, Math Class Needs a Makeover, and have been following his work ever since. If you haven't seen it, or his work, and you teach math or science, you should watch it. It's inspiring. And with a few tweaks, often by leaving out information, tasks become so much richer.
Anyway here is a stockpile of my posts about madeover labs with an inquiry or discovery focus:
Having a Ball with Chemistry: A good alternative to finding the thickness of aluminum foil, this experiment asks students to figure out if a bowling ball will float or sink in water and then test it out to see if they were right.
Isotopes Make Cents: Give students samples of pennies minted before and after 1982 and then a sample that is a mix of the two time periods. Ask them to try to figure out how many of each type of penny is in the sample without looking at the dates.
An Alien Periodic Table: There are many versions of this activity, but I like one where students have data about melting point, hardness, and color on cards and they try to arrange them into a periodic table of their own design. Then they get cards with all that information and also reactivity. They alter their original table to incorporate reactivity. Then they get cards with all that information and atomic mass and they incorporate that too. The next day in class, I provide them with a periodic table of these elements and ask them to do some predicting, based on the arrangement I provide.
Which Solution is Which? Put AgNO3, BaCl2, CuCl2, K2CO3, and NaOH into 5 beakers labeled A, B, C, D, and E. Don't tell students which solution is in which beaker. Ask them to figure it out. They can only use these solutions and a spot plate. Make sure they know how to predict reaction products first.
The Great Squid Challenge Buy Cartesian diver kits. Pass out supplies, show kids a model and ask them to create a working diving squid. After they do it, give a group 5 numbered droppers and ask them to put them all in a bottle and get them to dive in numerical order. Easy, cheap, safe, and fun.
Molar Mass of Butane Buy some cigarette lighters. Or get them from the assistant principals. Talk briefly about the butane inside, how it comes out as a gas. Challenge students to collect a sample and make the measurements they need to calculate its molar mass. Check in with them as they plan. They will need help with how to measure the mass of the gas.
Strength or Concentration? Make a 0.10 M solution of hydrochloric acid and a 0.10 M solution of acetic acid. Label them as A and B. Tell students one is a weak acid and one is a strong acid. Do the same with ammonia and sodium hydroxide solutions. Label them as solution C and solution D. Give students pH paper. Ask them to design an experiment to figure out if concentration or strength has a greater effect on pH.