How cold can it go?

Today we investigated the effects of adding salt to ice.

We added 2 tsp of salt to a plastic cup of ice and measured the temperature. Most group's ice temperature fell to well below minus 10 degrees Celsius.

We added 2 tsp more of salt and measured the temperature. It fell to between minus 15 degrees and minus 18 degrees. The plastic cups started to frost over!

Why did this happen?

Clue #1: We knew that salt helped ice to melt.

Clue #2: We also remembered that for ice to melt, the water/ice molecules need to be excited and start moving about more. That means the molecules need to draw in energy from somewhere, in order to excite and start moving...

After LOTS of discussion we worked out that the energy to excite the ice was coming from the air around the ice. If ADDING energy warms things up, then removing energy must make things COLDER! So the air around the ice was becoming colder, not the ice. The thermometer was measuring the temperature of the air, not the ice.

And boy, was the air around the ice COLD! Minus 18 degrees Celsius was the coldest reading we made. Did I mention that the plastic cups were frosting up?

What does this mean for Antarctica?

The salty ice all around Antarctica is melting, and energy is needed to keep the process going. That energy comes from the air, and as the energy transfers from the air to the ice, the air temperature drops! Brrrrrrrrrrrrrrr..... No wonder it's so cold down there!

Freezing Cold!

The Physical Nature of Ice
On Monday afternoon we experimented to find out what temperature salt water (sea water) freezes. We measured the temperature of normal iced water and found it was close to 1 degree Celsius. But when we measure the temperature of the salt (sea) water, the temperature dropped as low as -3 degrees Celsius.

What does this mean?

It might mean that...
Sea water needs temperatures lower than zero degrees celsius for ice to form.


Below are some other questions we are inquiring into this week:

What are the three states of matter?

What is the difference between a solid, liquid and gas?

What happens to molecules of water as they freeze? (see the two links below)

• Liquid Water
• Ice

Where does the energy go as water freezes?

History of Antarctica

As part of the 'excite and explore' phase of this term's inquiry on "Antarctica', we have been learning how Antarctica has, over time, gone from being a warm continent to a cold continent at the bottom of the world.

We learned that Antarctica was once part of a 'super-continent' called Gondwanaland.



We looked at the different shapes of the present day continents and how they might have fitted into the jig-saw of Gondwanaland.

Did you know that Dinosaurs once roamed the ancient forests of Antarctica, when it was part of Gondwanaland? Neither did we until yesterday!