Chances are that you separate mixtures often. For example, any time you separate laundry or pick a topping off a pizza or drain a batch of freshly cooked pasta, you are separating a mixture. A mixture is a combination of substances that do not react chemically when they are mixed. According to this definition, a solution -- such as sugar water -- is a mixture just the same as a mixture of sugar and sand.
In this experiment you will observe how rudimentary separating techniques are better suited for certain mixtures, while others require slightly higher technology. Mix uncooked rice, kidney beans and flour in a mixing bowl. Spread the mixture onto a large sheet of wax paper, and you'll notice that the beans are easy to see. Pick them out by hand and place them in a cup. Separating the rice from the flour, however, won't be so easy. Prepare a sieve by cutting out a square section of window screen large enough to fit over the bowl. Set the screen over the mouth of the bowl, and affix it with a large rubber band. Gather the wax paper into a funnel shape, and slowly pour the flour and rice mixture onto the screen. The flour will pass through, leaving the rice on top.
Separating a mixture of identical solids can be challenging until you identify a property that differentiates one from the other. Gather a collection of aluminum bolts and steel bolts, and make sure that both sets are identical. Then, mix the bolts thoroughly in a plastic bowl. Lower a bar magnet toward the bolts. The steel bolts are magnetic and will attract to the magnet as it gets close. As space on the magnet fills, remove the attracted bolts and place them in a separate container. Keep passing the magnet over the bowl until you have removed all of the steel bolts.
Mix plastic marbles and glass marbles together in two large bowls. Take one bowl for yourself and give the other bowl to a partner. Tell your partner he or she will have to separate that mixture by hand and that you will separate the mixture using only a cup of water. Predict who will be able to separate the mixture faster. Ready a timer, and fill a large cup with water. Start the timer, and let your partner begin picking out the plastic marbles. Pour the cup of water into your bowl and watch as the plastic marbles immediately float to the surface while the glass marbles remain at the bottom.
Have a friend create a batch of mystery mix for you to separate. Your friend can use any or all of the following ingredients: water, sand, sugar, soil and vegetable oil. When your friend presents the mixture, split it into several samples and perform experiments to identify its individual components. For example, if water is present, you can first try filtering the solution through a coffee filter to remove any sand or dirt. You could then boil the water to reveal the presence of sugar. If the mixture is dry but looks oily, you can add water to make the oil rise to the surface, and then skim it off.