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Friday, 26 February 2016

Changing States of Matter

Changing States of Matter

I started the day off with a quick check of background knowledge with a simple experiment I had carried out last year with my students. This invovled ice cubes melting in a glass of water and condensation occurring on the outside. Everyone was able to say what was happening to the ice cubes and some were able to explain why. Two students used the word 'condensation' but no one was able to explain how it occurred. So we proceeded.

Firstly we had a quick discussion about the states of matter: solids, liquids, gases, and I introduced them to two new ones of Plasma and Bose-Einstein Concentrate. It was much easier to understand what the atoms and molecules were doing if they acted it out. 

Getting up close and personal like solid matter 
Moving easily amongst each other like liquid matter

Escaping free like gas matter

Next we experimented with being able to change water into different states. They put ice (solid) into a pot and melted it into water (liquid). The challenge was to change the water into a gas (steam) and then through the process of condensation back into water again. Through this experiment with some timely questions everyone was successful and had a firm understanding of condensation.

Getting water to boil and change states to become steam
What did they notice when the hot steam hit the cold pot lid?
Many items can be classified easily but I wanted to challenge the kids to think about what makes a liquid a liquid? Some are easy to label like water and milk but others more difficult such as golden syprup and tomato sauce. We had to experiment to see if we could determine what was and was not a liquid. Some researching told us that liquids had a freezing point and a boiling point and they could be poured from one container into another.

We froze a variety of liquids such as honey, milk, tomato sauce and oil. We needed to see if they froze and if we could return them to a liquid state and then boil them. Did they give off a gas?

The honey was firm but not hard so that left a question in our minds.

The milk melted easily and was quick to boil

The honey smelt delicious but burnt very fast if not watched.

We discovered that all our frozen 'liquids' had a boiling point and were therefore officially liquids which led to the next student question of 'do all liquids have the same boiling point?' Luckily I knew we had some candy making thermometers in the resource room and everyone was soon boiling milk compared to water. They determined that water boils at 100 C and milk at 75 C so they don't have the same boiling point. Time was up. If only we had some milo!

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