Science - Unit E Day 2

Particle size is one observable physical property that can be used to separate mixtures. The word particle means a piece of a mixture of the same things. Look at the picture below.

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​In this cup, there are two different kinds of objects: sand, and orange math cubes. Each of the orange math cubes are a piece, or a particle, of all of the cubes in the cup. The cubes are mixed in with sand, which has much smaller particles, or pieces.

​When we put a handful of cubes into the cup, and we ask, "what are the orange particles," we would say "cubes." Because the cubes are large particles, we say "cubes" to talk about the entire collection. Sand is a special kind of mixture: if we ask, "what are the white particles," we would say sand. Would you say "sands?" Probably not!

​The orange particles are so large, that we could easily reach in with our fingers and separate them from the mixture. The sand, however, is too small to reach in with your fingers and separate every single particle. You might get some, or even most, with your fingers, but there's going to be some left in the cup.

​A strainer is a tool that we can use to pour a mixture through to separate small particles from a mixture. Strainers are also called colanders or sieves. A strainer has holes that are large enough for all the sand particles to fall through, but too small for the larger cubes to fit through. Using a strainer, we could separate all of the small particles of sand from this mixture.

Materials:

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​baggies, 3 per student/group

table salt

coarse seas salt/Kosher salt (not Epsom salt)

rock salt (if you can get it easily: not necessary if you don’t have it.)

plastic sifter OR paper cups: 1 per student/group with holes punched in bottom.

​1.Observe the bag containing a mixture of salts without opening the bag.

oThere are three different sizes of salt in the bag: table salt (smallest particles) coarse sea salt rock salt (largest particles)

oAll three salts are made of the same thing. The only difference is the size of the particles. 2.Think about how you will separate this mixture of salts based on particle size.

3.Open the baggy. Carefully pour the mixture of salts into the cup.

4.Pick the cup up, and hold the open baggy under it. Gently shake the cup.

5.Observe the smaller particles of salt fall through the hole in the cup and back into the baggy. Continue to gently shake the cup until all of the small particles of salt have fallen back into the baggy. 6.You have just used a strainer to separate a mixture based on particle size.

7.Now separate the remaining particles of salt from the mixture left in the cup, and arrange them by particle size.