You want more heat??!

Kirsti: Me compiling a post about heating my body up after some mighty heatwaves across Australia might seem somewhat of a surprise.

You may even wonder whether I may be lacking thermoregulatory capacities. Well, it’s true. I do lack them. I have pretty low blood pressure and to say my extremities get cold easily is the understatement of the year.

So mid-summer, post-heatwave, I bought some heat packs (yes, I realise this is a dodgy internet site). As you do.

In fact I bought a pack of those reusable awesome sodium acetate or ‘hot ice’ packs. I love the fact that there is a chemical reaction I can WATCH as my heat pack prepares itself to warm my tootsies in bed. Who doesn’t want some chemistry before bed!?!

This heat pack is a nice demonstration of how a super saturated solution behaves essentially under every day conditions, but having been treated with some interesting processes before I got my hands on it.  To be honest, initially I struggled with understanding exactly HOW this thing works. Now, I think I’ve worked it out…..with some help [thanks Chris Thompson!].

Inside my little pack is sodium acetate in a supersaturated solution. That is, the sodium acetate has been heated to some temperature at which you can dissolve much more of it than if it was at room temperature; kinda like how you can dissolve more sugar in hot water than you can in cold water.  Then if you cool it gently, it will stay saturated, and stay in a liquid state.  So sitting pretty with way more molecules of itself than it knows what to do with, when I click a little concave steel disc inside the pack, it creates friction – a fairly violent event – in the solution. This then becomes a nucleating site for crystallisation to occur. Crystals grow outward from the disc, and because it is an exothermic reaction, as it becomes a solid and appears as ‘ice’ crystals, it heats to around 54-57^oC. The heat will eventually dissipate and then I can melt the crystals back into their solution to once again anticipate warming my tootsies tomorrow night.

Watch the reaction here.

Thank you sodium acetate for also heating my feet when I’m camping without me waiting for the billy to boil…..

It’s another scorcher!

Kirsti: Having endured the past week, you might not be surprised to know that this time last year was also hot. It reached almost 50^oC in Moomba, South Australia in January 2013, and in Narrabri NSW – where we were driving a fortnight ago –  it reached almost 48^oC. In fact, have a browse of the daily extreme temperatures during January yourself – WA and QLD peeps are cooking eggs on car bonnets every day!

But this is not a post about climate change, even though it is contributing to these hot summers. It is about localised heatwaves, which are heralded if the temperature has been extreme for 3 days in a row; ‘extreme’ is relative to the time of year. You can check if there has been a heatwave in your area on an amazing website called Scorcher too, but it doesn’t tell you why it has occurred.

The thing is, heatwaves are caused by a complex combination of long- and short-term factors. Uber-long-term factors include global warming, both natural and man-made. Australia has warmed steadily since the 1940’s. But medium- to short-term factors are what interest me most at the moment. Warm winters preceding summer can increase temperatures across the continent, and high pressure systems (characterised by clear dry days) are also responsible for the local warming of air. Dry soils do not absorb heat as effectively as those holding water, which can act to heat the localised above ground air. But probably the most important is the fact that it is warmer more often and for longer periods of time. Recent heatwaves in Australia are essentially an extension of the preceding record breaking hot days, even months, exacerbated because it is mid-summer.

I would advise at this point to check the forecast and consider the previous month’s temperatures before embarking on a roadtrip into western NSW and southward.  Our two kids, trailer and 1996 Nissan Patrol can attest to it being one hot and sweaty trip spotting willy-willies, wheat and windmills!

NB: Image is a digital alteration of one of my own photos. 

[disclaimer: the heat + travelling in the heat is why I’ve been absent from here too!]

Curious curdling casein

Kirsti: Last night I wanted a milky honey drink, and thought I would sneakily sneak a little bit of lemon into it too.

Having previously experienced the curdling disaster of squeezing lemon into a creamy sauce, what I’m about to describe sounds ridiculous. Somehow, I thought I could get away without curdling my milky drink with my drops of lemon.

As I dripped the lemon in and hoped for the best, in the back of my mind I knew what was going to happen. My drink – which was boiling water, milk, honey and a few drops of lemon – curdled immediately.

Surprise, surprise. Not!

The curdling happened because the heat sped up the reaction between the clusters of milk protein (called casein micelles) and the citric acid in the lemon. Instead of being repelled from each other as they normally are in fresh milk, the micelles rapidly glumped (yes, glumped!) together. Bummer.

Temperature is a fabulous catalyst – it gets chemical reactions going quicker and more efficiently.

So I decided to do a little (non-replicated) experiment, and tried again with cold water.  No lumps!

But it turns out that even cold milk eventually curdles. The casein micelles start loving one another, a little bit at a time, albeit FAR slower thanks to the temperature of the drink. Happily, the teeny tiny little curdles that eventually occur in your cold drink will probably not put you off drinking it, if you detect them at all.

But I still have a problem: in cold milk and water, the honey doesn’t dissolve….ahhh, there goes science again!

Day 189. Blue-green algae

Today was damned hot in Adelaide: the maximum reached 39 degrees Celcius.

My decision to go for a run along the River Torrens was not a good one, given that (a) the sun was already fierce and temperature high, although only 8am and (b) the water-way was a stinking, stagnant mess.

This shot shows blue-green algae just near the Adelaide Zoo-section of the river.

Blue-green algae is a misnomer: the growing mass is actually comprised of a type of bacteria called cyanobacteria. Although a natural part of the freshwater environment, according to the Murray-Darling Basin Authority,

“If conditions are favourable, they reproduce at very high rates to form ‘blooms’ – explosions in growth that dominate the aquatic environment, forming unpleasant and sometimes toxic scums.”

Blooms arise when non-flowing pools of water collect in sunny, protected areas: this in turn allows a layer of warm, sun-drenched water to sit at the surface and create perfect conditions for the cyanobacteria colonies to multiply. Like plants, the bacteria generate their own source of energy by photosynthesis.

Water containing blue-green blooms is not fit for swimming or consumption due to the toxins produced by the bacteria. Amazingly, today I saw two little water birds paddling about in the scum shown in the image. I hope their health is still good.

Blooms in the River Torrens have been triggered by recent hot weather combined with low rainfall in South Australia: what we need now is a little rain and a drop in temperature to clear it up.

Tommorow’s forecast is minimum 27 degrees, maximum 39 again.