Grade 5: Discovery Museum’s
Physical Changes of Matter Workshop
October 27 & 28, 2014
Matter is what makes up everything. Matter is made of atoms and molecules. Matter
has certain properties: it has volume (takes up space)- it has mass (weight) and it has
shape
Does sound have mass? Volume? Shape? It does not – sound is a form of energy
There are three states (phases) of matter:
1. Solid
2. Liquid
3. Gas
Students used their hands to model the movement of molecules in solids, liquids and
gasses.
Solid: Molecules are tightly packed.
Liquid: Molecules are not so tightly packed. Liquids take the shape of their container.
Gas: Molecules are moving. Gas takes up the most space.
In the workshop, students observed three types of matter:
1. Water (H2O)
2. Carbon Dioxide (CO2)
3. Nitrogen (N2)
1. Water molecules are called H2O because they are made up of two hydrogen atoms
and one oxygen atom.
During the workshop, some teams of students were given ice (frozen water) and
challenged to change its state of matter in two minutes. A spokesperson from each
team reported two things:
1. Method (What did you do?)
2. Result (What happened?)
As a result of this experiment, students learned about physical changes of matter.
Physical changes: With the addition of heat, matter changes from a solid to a liquid to
a gas. With the removal of heat, liquid changes from a gas to a liquid to a solid. (This is
different from a chemical change, such as mixing vinegar and baking soda. In a
chemical change, the matter changes permanently.) Physical changes are reversible
and molecules stay the same during a phase change. A chemical change (burning
wood) is not reversible and molecules change.
Evaporate
Melt
Liquid
Solid
Freeze
Gas
Condense
2. Carbon dioxide molecules are called CO2 because they are made up of one carbon
atom and two oxygen atoms. Carbon dioxide is the gas we breathe out. Plants take in
carbon dioxide and give us oxygen, which we take in.
Frozen carbon dioxide is called dry ice. Carbon dioxide freezes at very cold
temperatures (−78.5 °C or −109.3 °F). If you handle dry ice, you should wear gloves to prevent
burns by freezing (frostbite). Dry ice is a solid that changes to a gas when warmed. It does not
melt or evaporate, it sublimates (turns from solid directly to a gas).
Remember that gas takes up more space than a solid. When dry ice sublimates, it
expands. Students observed this happening in the following ways:

Dry ice was placed inside a balloon, and the balloon was tied. The sublimating carbon
dioxide blew up the balloon!

Dry ice was placed inside an empty film container, and the cap was snapped on tightly.
The sublimating carbon dioxide popped off the cap!

Dry ice was placed into a container of water and a cap with a hole was added. Students
observed sublimating carbon dioxide escaping the hole (it looked like white steam).
Sublimate
Solid
Liquid
Gas
3. Nitrogen is called N2 because a molecule of nitrogen is made up of two nitrogen
atoms. It is a gas, but at extremely cold temperatures (-150°C or −230 °F) it becomes a
liquid. This liquid is called liquid nitrogen. Our atmosphere is made up of 75%
nitrogen.
When poured liquid nitrogen will evaporate very quickly. Wear safety glasses and
gloves when pouring liquid nitrogen.
Because liquid nitrogen is so cold, students were able to observe the following:
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Carnations completely froze when placed in liquid nitrogen for just one second!
A banana froze so completely when placed in liquid nitrogen that it could be used
as a hammer!
Rubber bands became hard and brittle when placed in liquid nitrogen, and would
crumble when crushed. However, when friction was used to add heat, they
regained their elasticity.
A balloon filled with air and tied, when placed in liquid nitrogen, shriveled and
deflated because the air inside the balloon became cold and its molecules
became tightly packed.
A metal ring that normally fit around a metal ball, after being placed in liquid
nitrogen, became smaller (its molecules squeezed together more tightly) and the
ring no longer fit around the ball. However, when the metal warmed back up, it fit
again.
When liquid nitrogen was poured into a tea kettle, it made the kettle whistle.
Ping pong balls, filled with air with tiny pinholes, rolled quickly after being placed
in liquid nitrogen.
Liquid nitrogen was poured across the classroom floor. Students could see
crystals form as it traveled.
Here is the website that you can access to get information about the Discovery Museum
and get your free admission pass;
http://tinyurl.com/TSWactivity