Liquids & Solids Part 2: Turning Milk into a Solid
2nd grade, 25 students
1 hour
Materials:
 Airtight jar (plastic or thick glass)
 Another container & spoon to stir
 Marble
 Heavy whipping cream
 Red bull
 Observation Worksheet
 For tasting: plates, crackers, plastic knives
Procedure:
1. Liquids can have compounds in them that can be aggregated to form a solid. Ex:
milk has fat particles that can be stuck together to create solids.
2. This can be done in at least 2 ways: chemically and physically
a. Chemically- when the right chemical (ie Red Bull) is mixed with the milk, it
causes the fat particles to separate from the rest of the milk joining together
to create fatty residue
b. Physically- when agitated, the fat particles are knocked together enough so
that they stick together, creating butter, and leaving a thin film of liquid ‘fat
free’ milk on the top.
3. Now demonstrate! (pass out observation worksheets)
a. Chemical separation- pour some cream into an open container. Add some
Red bull. Stir. After a minute or two and maybe more Red Bull, you will see
what looks like stiff foam on the top- the solid.
b. Physical separation- pour .75 pint of heavy whipping cream into an airtight
container with the marble inside. Shake (with students) for ~15 mins & sing
“Shake It”.
4. Ask students for their observations; discuss
5. Eat the butter on crackers 
Observation Worksheet: Turning Milk into a Solid
Chemical Separation
Physical Separation
Milk mixed with Red Bull
Milk shaken by you!
Milk before chemical reaction
Milk- before physical separation
Texture- how does it feel?
Texture- how does it feel?
Density- is it hard or soft?
Density- is it hard or soft?
Volume- how much space does it take?
Volume- how much space does it take?
State- solid or liquid?
State- solid or liquid?
[[Flavor- what does it taste like?]]
Flavor- what does it taste like?
Milk after chemical reaction
Milk after physical reaction
Texture- how does it feel?
Texture- how does it feel?
Density- is it hard or soft?
Density- is it hard or soft?
Volume- how much space does it take?
Volume- how much space does it take?
State- solid or liquid?
State- solid or liquid?
[[Flavor- what does it taste like?]]
Do not eat this! Edible? Yes, but…
Flavor- what does it taste like?