Lesson 3.1 Separating Mixtures

You use mixtures every day.  Sometimes you need a mixture; other times you need to separate a mixture into its components. 

Japanese macaque monkeys have been fed by people for quite some time.  They scattered sweet potatoes and wheat on the beach.  The monkeys had plenty of problems eating the potatoes which were covered with sand.  Have you ever eaten a piece of food that had only one grain of sand in it?  It is a terrible thing to bite into and hurts the teeth as well as damaging them.  The monkeys would spend much time rubbing as much of the sand off the potatoes as possible.  How would you remove all the sand from the potato-sand mixture?

"In 1953, a one and a half-year-old Japanese macaque named Imo discovered that she could wash the sand from sweet potatoes by rinsing them in water before eating them. After four and a half years, 18% of the adult monkeys and 79% of the juveniles in the troop had learned the potato washing technique by imitating Imo. In 1961, all monkeys born later than 1950 had acquired the technique except one. Masao Kawai has studied the spreading pattern for the potato-washing behaviour and documented a connection with the social structure."
The wheat and sand mixture was also a problem.  The monkeys would pick each grain of wheat carefully from the beach and eat it.  This was a very tedious procedure to get a little food, and the occasional grain of sand picked by mistake proved painful.  How would you separate the wheat-sand mixture? 
"In 1956, Imo made another discovery. She found out that she could separate wheat grains from sand by dropping them into the water so that the wheat grains would float and the sand grains would sink. This invention has spread in a similar way." (Kawai 1965; Watanabe 1994).

This Imo was a very smart monkey, don't you think?  People need to separate the components of mixtures as well.  The metals, fuel, water, and other substances that you rely on each day must be separated from mixtures. 

Read Separating Mixtures on page 50. 

Question 1. What are at least two things that must be separated from dirty water before it is safe to drink?

Question 2. What is the mixture that is being separated in Off The Wall on page 50?

Question 3. How are gold particles separated from the sand that is dug from a river bed?  Hint: read Did You Know on page 50.

Check your answers with those that follow.

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. What are two things that must be separated from dirty water before it is safe to drink?

There are at least three things that must be separated from dirty water before it is safe to drink.
·    large particles such as sticks, leaves, and mud
·    bacteria and other microorganisms
·    dissolved chemicals

Question 2. What is the mixture that is being separated in Off The Wall on page 50?

The mixture is air and water.  Fog is actually tiny droplets of water mixed in the air. The nets are used to separate the water from the air.

Question 3. How are gold particles separated from the sand that is dug from a river bed?  Hint: Read Did You Know on page 50.

Gold particles (flakes or nuggets) can be separated from the sand by using a method called panning.  The less dense sand particles are washed out with water, leaving the more dense gold particles in the bottom of the pan.


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