Tuesday, 29 April 2014

Kitchen chemistry - molecules, changes of state and solubility

We have been performing some experiments this week from a free online course by Futurelearn called kitchen chemistry which we have been following. I haven't gone into too much detail here as I am rushing (and failed to take any photos at all!), but it is still possible to register for the course and use the resources. Harry loves science and is always really engaged so he has enjoyed this week!

Yesterday we went to a friend's house and did some work about the behaviour of molecules in solids, liquids and gases and changes of state, including talking about density, watching a BBC class clip and performing several experiments. 

- We heated the inside of a plastic bag using a toaster. The plastic bag fills with warm air, which takes up more room, so it flies into the air like a hot air balloon.

- We used an unfolded tea bag (the kind with a staple and string, emptied of it's contents) which forms a tall, hollow cylinder. This was lit with a match at the top and, as it burnt down it created a column of hot air. The very last scrap of the teabag cylinder flew into the air up this hot column. This experiment was greeted with shrieks of delight from us all and we did it several times! This is the image from the course pages.

- We squashed butter from the fridge (inside food bags) in our hands to warm it and make it spread out and turn into a liquid state.

- We observed ice melting inside a small bowl to form a liquid, and how the liquid takes the shape of the bottom of the container it is in.

- We dripped melted candle wax into very cold water to observe it turning back into a solid.

We took an experiment from the course to the church hall for our group session this morning too, based on separating materials. We mixed a soluble material (salt) with a non-soluble material (coffee grounds) then talked about how we would separate them. We added water then filtered the water using a tea strainer. This filtered out the coffee grounds and left a salt solution. To recover the salt, the water needs to be evaporated off. There is a BBC class clip on this topic too, which we found and watched at home.

One of our friends brought a solubility experiment too. All the children were given a material - cocoa powder, baking powder, flour, jelly crystals, bicarbonate of soda, salt or sugar. They added a spoonful to a cup of cold water and we recorded the results, looking for whether it had dissolved. They then added a spoonful to a cup of hot water to observe any differences. We concluded that the hot water speeds up dissolving for some materials (jelly) and for others (cocoa powder) helped it to dissolve where it hadn't before.

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