1. Engineering Mixtures: Separation Anxiety
SISSI 1 Grades 3-5

2. Essential Questions
How can properties of substances be used to separate various mixtures?
How can the Engineering Design Process be used to find the most efficient procedure for separating mixtures?
Give each group containers with a physical mixture of different items to separate: a cup with different colored beads and pieces of pipe cleaners the same color as the beads. Discuss different ways to separate them according to different properties (color, shape). Go over Essential Questions: How can properties of substances be used to separate various mixtures? How can the Engineering Design Process be used to find the most efficient procedure for separating mixtures? Elicit prior knowledge.

3. Separating Mixtures
1. How can you separate any two things that are next to each other?
2. How can you separate items made of iron from items with no iron?
3. How can you separate things dissolved in a liquid? (the solute from the solvent)
4. How can you separate items of different sizes?
5. How can you separate dissolved items from items that are not dissolved?
Remind students that a mixture is a physical combination and that it can be separated by physical methods. Ask:
How can you separate any two things that are next to each other?
Possible answers: Pull them apart; push them apart.
What could you use to pull one thing such as a piece of iron, from another?
You could use a magnet.
What method could you use to separate two things that have different densities?
Possible answer: You could let the denser material settle to the bottom, and spoon or pour the less dense material off the top.
Quick Check
Infer: Two liquids boil at about the same temperature. Would it be easy to separate them by distillation? Why or why not?
No. Distillation uses evaporation and condensation to separate a liquid mixture. Two liquids with a similar boiling point would likely evaporate and condense at about the same time, making them hard to separate.
Critical Thinking: How could you separate clean air from smoke?
Smoke is a colloid, a mixture of particle in air. It will not settle as a suspension does. The particles in a colloid must be filtered out, just as with sand and water, but with a much finer filter.
7. How can you separate pigments or inks from each other?
6. How can you separate items of different densities?

4. Magnetic attraction
separates magnetic material from a mixture of other substances.
Example:
A cow magnet, is given to a cow to swallow.
It stays in the first part of the cow’s stomach,
keeping magnetic materials like wire and
other harmful materials that cows swallow
from going into the rest of their digestive system.

5. Evaporation separates a solid that has dissolved in a liquid solution.
a. The solution is heated or left uncovered until all the liquid turns to a gas (evaporates) leaving the solid behind.
b. Example:
Salt in salt water or ocean water, for example, is separated by heating the solution until all the water evaporates leaving the solid salt in the container.

6. Sifting separates smaller solid particles from larger solid particles.
Examples:
Cooks sift flour to get a small particle size for baking leaving larger particles of flour in the sifter above the screen.
Sand and gravel companies, for example, separate rocks into different sized particles for road building and other construction projects using this method.
Archeologists use sifters to find small artifacts in the soil.

7. Filtration used to separate solid particles from a liquid or gas.
a. Pouring the mixture through a filter paper in a funnel will trap the solid particles and only allow the particles of the liquid to pass through.
b. Example:
Water treatment plants use this as
part of the process for separating dirt and
other solid particles from water to produce
clean drinking water.
Show participants how to put together the FOSS filtration stand and how to fold the coffee filter.

8. Flotation
separates solids that float from the remaining liquid in a mixture.
a. The solids are stirred and when they float to the top, they are skimmed off the surface of the liquid and put into a different container.
b. Example: This method is used in some water purification plants by letting solids float to the top.

9. Chromatography used to separate and analyze the solutes in a solution.
a. A small amount (2-3 drops) of the solution is put on a piece of filter paper, which is put in a solvent.
b. The substances in the solution that dissolve most easily travel the furthest; and substances that do not dissolve easily do not travel very far.
c. Example:
Scientists use the bands of color that are formed
to identify the substances in the solution by
comparing them to the location of known
substances forming bands of color on different
filter papers.

10. Explore Engineering Design Process
ASK: What is the problem? How have others approached it? What are your constraints?
IMAGINE: What are some solutions? Brainstorm ideas. Choose the best one.
PLAN: Draw a diagram. Make lists of materials you will need.
CREATE: Follow your plan and create something. Test it out!
IMPROVE: What works? What doesn't? What could work better? Modify your designs to make it better. Test it out!

11. Explore
The Goal
A supply truck carrying diatomaceous earth to the Bright Toothpaste Factory collided with a truck carrying iron filings to the Magnificent Magnet Company. The collision happened on a gravel road going through a salt marsh. The accident resulted in a giant mixture of materials from the trucks as well as the ground around it.
Fortunately, no one was hurt. Unfortunately, the mess needs to be separated so that the valuable loads can get to their destinations.
A $1,000,000 clean-up contract will be given to the team that can best separate the mess into the original substances!
Your goal is to find the most efficient method for separating the ingredients in a mixture of gravel, diatomaceous earth, iron filings, leaves/sticks, and salt. Each substance should be as pure as possible and as close as possible to the starting amount.
Diatomaceous earth is a naturally occurring, soft, siliceous sedimentary rock that is easily crumbled into a fine white to off-white powder. It consists of fossilized remains of diatoms, a type of hard-shelled algae. It is used as a filtration aid, mild abrasive in products including metal polishes and toothpaste, mechanical insecticide, absorbent for liquids, matting agent for coatings, reinforcing filler in plastics and rubber, anti-block in plastic films, porous support for chemical catalysts, cat litter, activator in blood clotting studies, a stabilizing component of dynamite, and a thermal insulator.
Students should put the goal in their own words on their Data Sheet

12. Explore
Ask/Imagine
What do we know about the properties of each of the ingredients?
What do we know about ways to separate various materials?
Brainstorm ideas to separate the substances.
Students should explore the ingredients’ properties and fill out the top chart on their data sheet. Students should brainstorm as a group and share with class if desired.

13. Properties of Materials
Explore
Properties of Materials
Use the materials in your tub to explore the properties of gravel, diatomaceous earth, iron filings, leaves and sticks, and salt.
small no no
yes
small no no no
small
No/yes
yes no
Med/large
yes no no
large no no no

14. Explore
In a Ziploc bag, make a model of the mixture caused by the truck collision. As you work, you may put together another mixture if you need to.

15. Explore
Plan
Talk with your group to plan the methods and the order that you will separate the materials.
Write your plan on your data sheet.

16. Create Improve Create Improve…
Explore
Create Improve Create Improve…
Use the materials in your tub to find the most efficient way to separate your mixture.
As each substance is separated, measure its mass in grams on the digital scale and place it in one of the courtesy cups.
Improve the steps as you go. You may make another bag of the mixture if you need to. Record your results on the data sheet.

17. Evaluate
Communicate
Choose one person from your group to report your results to the class.
Students should report using the questions on the back of their data sheet.

18. Mixtures Separating Song
Extend
Just for fun…
Mixtures Separating Song

19. Success? Reflect on: how you would improve your design
how the group used each step of the engineering design process.