Jamie asked a question – “Why does water sometimes boil at different temperatures?”

I must apoligise to Jamie because he specifically asked about the water in Yellowstone River boiling at 106 0 C.  Why does it do that? Does water boil at a higher or lower temperature in other situations? I asked my friends about this.

Jamie, the properties of water does depend on it’s intermolecular structure. If it didn’t have these intermolecular forces (called hydrogen bonds) the water would likely be a gas at room temperature. Life on Earth would therefore be impossible or maybe very different.

Ok, water is as it is now, so why can it’s boiling point change? The main reason is the environment in which it is trying to boil, not the water. Boiling is linked to the process of the water molecules getting enough energy from the heat source to make it move so fast that the intermolecular forces can be broken and it can escape from the water into it’s environment.

BUT

If the environment is changed this can affect the boiling point. Make the environment thicker(more dense) and the water molecules have greater difficulty in escaping making the boiling point go up, in the kitchen a pressure cooker prevents the faster water molecules from escaping.  Make the environment thinner (go up a mountain, where the air is ‘thinner’) and you make it easier for the water molecules to escape so the boiling point goes down.

HOWEVER

There is another way to affect the intermolecular forces of the water molecules. Introduce something into the water that increases the intermolecular bonding. Introducing salt NaCl, which gives Na+ and Cl ions in water. These make it more difficult for the water molecules to become gaseous molecules so the boiling point go up.

There are other posts that could help you…..On intermolecular forces and a game you could play and adapt.

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