There are two words that come to mind when trying to engage uninterested students in any subject: fun and relevance. If you can make the subject relevant to the student, you are halfway there. If you can make it fun, you are home and hosed because it is much easier for someone to learn when they are having fun. Luckily chemistry is potentially a very fun subject if the teacher is willing to make the effort and it is also relevant because chemistry is the key to how things work. When I introduce students to the Periodic Table, I like to tell them that they are looking at the key to understanding the Universe. Perhaps that is a bit of an overstatement but it is the key to how all substances are made. Understand the Periodic Table and you can begin to understand where we came from and how we are made.
A lot of students are hard to hook with the relevance argument though. Their attitude is that they don’t have to understand something in order to use it. So that is where the fun has to come in. There are many fun and interesting experiments in Chemistry, starting with using the Bunsen burners. Boys are the easiest to engage when there is fire involved. Give them a box of matches and they will usually engage themselves, although not always in safe and appropriate ways! The main problem with boys and fire is safety and you have to make and enforce the rules when using Bunsen burners, but once that is done even boiling water and measuring its temperature can be fun.
Almost every young boy I have had in my chemistry classes has asked me if we can blow something up. This can be a huge safety problem but I have found several labs that satisfy the need to explode something. Magnesium metal in small strips can be burned like fireworks or it can be dissolved in acid to make hydrogen gas, which when exposed to a flame will explode with a satisfying POP. Check out this site for the method: http://chemistry.helium.com/how-to/9814-how-to-make-hydrogen-gas-from-magnesium-and-hydrochloric-acid
The other explosive experiment is actually an implosion and involves nothing more than some water, heat and an aluminium soft drink can. Heat a small amount of water in the can till steam rises out the opening, then turn the can upside down in cold water: woomph! The can collapses as the outside air pressure pushes against the vacuum in the can created when the steam turns back to water. The students love this experiment and will perform it over and over until the bell rings or the cans run out. The method is available here: http://physics.helium.com/how-to/9756-how-to-implode-an-aluminium-can-to-demonstrate-the-power-of-air-pressure
Edible experiments are also fun and relevant to the average teenager. Making ice cream from real cream using salt on ice to drive the temperature down is much more effective at teaching students about latent heat than ‘chalk and talk’ and most young people will be amazed at how tasty real ice cream is. (See http://food-drink.helium.com/how-to/9588-how-to-make-ice-cream-by-hand ) Making sherbet is a fun way to teach the reaction of an acid with a carbonate base (See http://food-drink.helium.com/how-to/9833-how-to-make-a-fizzy-sherbet-treat-from-an-acid-and-a-base )
Basically the less blah blah blah and the more interesting experiments that the teacher can employ, the more chance there is of engaging disinterested students. Often the disinterest stems from difficulties with literacy and numeracy. These students learn much better from hands-on experiments than copying words from the board that they do not understand. The key is finding the ‘hook’ that will capture the student’s interest. It may be food or fire or something intriguing like telling the students they can make milk into plastic ( http://chemistry.helium.com/how-to/9957-how-to-make-a-plastic-from-milk ) or boil water in paper ( http://chemistry.helium.com/how-to/10296-how-to-boil-water-in-paper ) Then the key is to slip in the science with the fun to show the students how a little knowledge can lead to interesting results and new discoveries that could benefit them in their own lives. It’s not easy and being a Chemistry teacher and sometimes requires nerves of steel but the results are worth it if the disengaged student suddenly becomes passionate about Chemistry.