Sunday, August 3, 2008
Thursday, July 31, 2008
Friday, July 11, 2008
Polymer Day! Polymer chemistry is a HUGE business. We could spend weeks just looking at polymers... but we won't. We will just spend one day making and testing different polymers. First we have to learn that a polymer is a long chain of molecules. When polymers are combined with a "linking agent" the long chains get "linked" together and become stiff, rubbery, or really really viscous! We made three different polymers today and then tested them for things like "slimyness", "bouncyness" and "viscosity". We also subjected them to the "poke test" as well as the "hang time test". Most of all, we just had fun making our polymer "boogers" look like they were coming out of our noses!
Follow this link to find the recipies and more fun about polymers...
Thursday, July 10, 2008
Alka Seltzer Day! Everyone loves Alka Seltzer Day! We used Alka Seltzer to explore the collision theory of reaction rates. In order for chemical reactions to occur three things must happen: the particles MUST collide (hit each other); they must collide with the right orientation (hit in the right place); and they must collide with the right amount of energy. How then are reaction rates affected by things like temperature and particle size/surface area? THAT is what we found out today. We tested pieces of Alka Seltzer tablets in room temperature, cold and hot water and timed how long it took for the reaction to finish. We also tested the difference between big pieces, chunks and powder! What did we find out? Ask us to tell you when we get home. THEN we went outside and used what we learned about reaction rates to create the perfect Film Canister Rocket. One thing that was clear from the start... the fastest reaction may NOT be the best to make the perfect rocket! (Note for those trying it at home... you need Fugi type film canisters with the lid that snaps inside the canister to make the rockets)
Wednesday, July 9, 2008
Chemical reactions come in 1000's of shapes and sizes! Chemists don't memorize them all... we learn to categorize them! The five main categories for chemical reactions are: Synthesis (put together), Decomposition (take apart), Single Replacement (an element replaces another that is bonded in a compound and kicks it out), Double Replacement (ions in two compounds switch partners) (Double Replacement includes most acid/base reactions) and Combustion (MEANS COMBINES WITH OXYGEN! NOT EXPLOSION). Today we did a bunch of "mini experiments" and chose a category for the chemical reaction. We also paid close attention to changes in energy. Reactions that need or absorb energy to happen are called "endothermic". Reactions that give off energy as a product are called "exothermic". We also discussed what a catalyst is and how it works. It is a good bet that the only thing we are going to remember about today is BURNING MAGNESIUM!
Tuesday, July 8, 2008
Entering the CHEMICAL world! Now that we have spent several days looking at the Physical side of matter... we will spend some time with the Chemical side. Chemical properties and changes are those that can only be seen while a substance is in the process of changing into something else. Today we are doing a bunch of "mini experiments" and deciding if we are observing Physical or Chemical changes. It is not so easy to tell. What exactly IS happening when we burn a candle???? Ask us when we get home, we know!
Saturday, July 5, 2008
Saturday and we are checking out solutions... as we learned the other day, solutions are mixtures of two or more substances. Solutions can be unsaturated (not full), saturated (full) or supersaturated (overfull). Heating up solutions allows you to dissolve more solute (stuff being dissolved) into the solvent (stuff it is being dissolved in) then it can normally hold. Today we made supersaturated solutions of Borax. We are going to use our supersaturated solutions of Borax to create "snowflakes". As the hot solutions cool, they can hold less Borax. The Borax "crystalizes" out and sticks to our pipecleaner snowflakes. When we come back to class we should see some really cool stuff!
We also spent time today to investigate the "Wonders of Water". Water is a really unique substance. Besides being a really good solvent for solutions, it also has some really cool properties. Water molecules have REALLY strong bonds. This causes it to have strong COHESION (water clinging to water) and ADHESION (water clinging to other stuff). These properties of water allow us to make water "walk along the string". Water's strong surface tension is responsible for really cool activites like the "magic jar" (ask us to show you when we get home... shhh it is a secret how it works) and the "bubble on the penny". Water also has a really high HEAT CAPACITY. This means that it absorbs and holds on to lots of energy. A property that is really important in the concepts of Earth Science and Weather. Water's heat capacity is so high that we can boil water in a paper cup! We know! We did it!
Friday, July 4, 2008
Elements, compounds and mixtures! That is the focus of days three and four. All matter can be put into one of those groups. Elements are the purest form of matter. Compounds are a combination of elements that have been chemically bonded to each other. Mixtures are a blend of two or more substances that have been physcially combined. We consider elements and compounds to be "pure substances" because they are made up of only one type of substance. Mixtures can be either homogeneous (all the same) or heterogeneous (see different parts). Solutions are homogeneous... things like granite, chinese food, and soda are heterogeneous. On day three we worked on separating mixtures. First we separated a mixture of four different types of plastics and iron filings. We used any tools that we wanted and figured out the best methods of separation all by ourselves! Great teamwork! Next, we took a sample of "FOUL water" and used some standard separation techniques to clean it up... we allowed the oil to float to the top, then we filtered through gravel and sand, then we added charcoal that absorbed odors and filtered it through filter paper. Even though it looks REALLY clean now... we still have to test it to see if it conducts electricity... when it does we know that it still contains something dissolved in it like salt. To get rid of that we have to distill it.... now it is clean... but NO you can not drink it! YOU DON'T DRINK ANYTHING THAT HAS BEEN IN CHEMISTRY GLASSWARE!
One day four we tried out some more separation techniques... first we separated the different colors in markers using chromotography. We made cooooool round chromotographs. Chromotography separates the dyes by washing the different molecules along the paper. The different molecules (colors) have different attractions to the paper, so they stop in different locations. Next we separated a mixture of shaving cream and food colors using the food colors attraction to paper. This is a cool technique and we used it to make special "postcards" which many of us mailed home!
Tuesday, July 1, 2008
Our second day of chemistry and we are diving right in! Today we talked about "Properties" of matter. Two kinds... Chemical and Physical. Today we focused on Physical Properties. A property descibes a substance. It also allows us to identify it and put it into categories. There are two types of properties... "quanitative" which are properties that involve measurements and numbers; and "qualitative" which are those that do not involve numbers. "Patti is short" is qualitative... "Patti is 5'1" tall is quantitative". In chemistry we need to make both kinds of observations. Chemists all over the world compare quanitative properties with each other using the metric system of numbers. Our task today... investigate the physical property of "Density". Density is actually a relationship between two physical properties... mass and volume. Quantitativly, it is the ratio of a substances mass divided by it's volume. Qualitativly it represents how closely packed the particles are in a sample.
We investigated density in two ways today. The "Liquid Density Challenge" in which we compared the densities of 5 different liquids and arrived upon the proper order from least to greatest density. Then we performed the "Golf Ball Float" challenge where we add salt to water in measured amounts to make the golf ball float in the center of the container... once we know how much salt we added, we can figure out the density of the salt water solution. Whew! Busy day!