Fun Friday – Exploring Density

What is Density?

Density is the mass of an object per unit volume.  A bit of a mouthful but this is how I explained it to my own children today….

…imagine you have a pebble and a marshmallow of the same size and shape… which one do you think is heavier?

My three year old got this straight away… “the pebble of course Mum” (with a “silly question” look that I am use to at this stage).

The Fun Friday Science Team!

So if they are the same size (volume) then why does one weigh so much more than the other?  If you remember that everything is made up of molecules… the heavier object simply has more molecules packed more tightly together (a greater mass); the molecules in the lighter object (in this case the marshmallow) are much more loosely packed together (a smaller mass)!

The pebble is said to have a greater density than the marshmallow.

A bit of History:

A Greek scientist called Archimedes (250 BC) is credited with discovering the concept of density.  The story goes that Archimedes was given the task of determining if the newly minted King’s gold coins were genuine (or if they had been mixed with silver).  Archimedes was pondering this idea while lowering himself into the bath.  When he noticed how his body displaced a volume of water he realised he had cracked it!  If he compared a coin of pure gold with the newly minted ones he could check if they displaced the same amount of water i.e. that their densities were the same.  Turns out they were not and the King was beings duped!

They say that Archimedes was so excited when he realised the solution that he jumped out of the bath and ran all the way home naked shouting “Eureka, Eureka”…. (“I found it, I found it” in Greek).

Here are some experiments on density that you can try at home…

The children and I spent the afternoon trying out these cool experiments that are easy to do at home.  Hope you get to try some too!

1. Make a density rainbow

You will need:

A clear glass, golden syrup or honey, maple syrup, milk, washing up liquid, water, food colouring, cooking oil or baby oil, a clear alcohol (we used isopropanol but you could use methylated spirits or vodka – with adult supervision!), funnels, a dropper or a spoon.

What to do:

Place some water in a glass and add a few drops of food colouring and mix. Place some alcohol in another glass and add a few drops of a different food colouring. Mix.

Carefully add each layer in the following order….

  1. golden syrup
  2. maple syrup
  3. milk
  4. washing up liquid
  5. coloured water
  6. baby oil (or cooking oil)
  7. coloured alcohol
Try to add each layer carefully down the side of the glass, using a spoon, a dropper or a funnel (as below).  Make sure each liquid makes a complete layer that fully covers the layer underneath.  If the layers mix a little, allow to settle before adding the next layer.
Add each layer carefully down the side of the glass
Two junior scientists admiring their work!
We think it looks lovely!

What is happening:

We added the most dense material first (the golden syrup) and then the next dense and so on.  So each layer is a little lighter or less dense than the previous one and therefore floats on it.

You can of course add other things are leave some of these layers out!

2. Lava lamp in a glass

You will need: a clear glass, sunflower/vegetable oil, water, food colouring, some effervescent tablets such as AlkaSeltzer.

What to do: Place water in the glass to about one third full.  Add a few drops of food colouring to the water and mix. Gently pour the oil down the side of the glass filling the glass to almost the top.  If the oil and water mix a little don’t worry, just wait a while until the two layers separate out with the oil sitting on top of the water. Break the tablet into pieces and add one or two pieces to the glass…. I will let Caer explain it to you (with a little prompting from her brother)!

What is happening:

When the AlkaSeltzer tablet reaches the water layer it starts to dissolve and fizz, releasing a gas called carbon dioxide.  This gas forms in small bubbles surrounded by water, they start to rise to the top of the glass because the gas is lighter (less dense) than the water and oil.  The bubbles pass all the way through the oil layer to the top of the glass where the bubble eventually bursts, releasing the carbon dioxide gas.  Once the gas is gone the bubble is just water, which is heavier (more dense) than the oil so it starts to drop down again.  The process continues until all the carbon dioxide has escaped to the top.  Adding more AlkaSeltzer starts it all off again!

3. Fireworks in a glass

You will need: A glass, water, food colouring and sunflower (or vegetable) oil

What to do: Fill the glass with water to about two thirds full.  Carefully pour a layer of oil on top of the water to fill the glass.  Add drops of food colouring to the top of the oil layer and watch as they slowly drop down and enter the water layer.  They streak through it like some mini fireworks!

Add the drops of food colouring to the top of the oil…
…and wait for the fireworks display to begin!

What is happening:

Food colouring and oil do not mix so the drops will fall until they meet the water layer.  Food colouring dissolves in water, the colour diffuses out into the water as the drops fall to the bottom of the glass, giving a lovely fireworks type display!

Hope you enjoyed this week’s Fun Friday as much as we did.  If you have any comments, questions or suggestions please leave a comment below, I always love the chat and feedback!  

Have a great weekend!

Back to school – the lunchbox dilemma!

Summer holidays are finally over and my three children were up EXTRA early Monday morning with the excitement of the return! To be honest I had mixed feelings but was encouraged by their enthusiasm.  We had a great Summer and I really enjoyed the break from the schedules and routines… but most of all I enjoyed the break from having to prepare the lunchboxes every morning!!!

The break has done me good… I am returning to the challenge with renewed vigour and optimism… for the moment anyway.  No doubt within a few weeks I will be reduced to the early morning cold sweat… wondering what I have in the cupboard and WHAT I am going to feed my super fussy son who believes there are only two food groups worth mentioning… Meat and Sugar!

To ease us all into things and to give myself a bit of a head start I did spend some of the Summer modifying a flapjack recipe.  The fussy one does love flapjacks and the original recipe was from Rachel Allen’s Food for Living Cookbook.  They are heavy on the butter and the sugar and taste sooo good!  I decided that if I could make them a little more healthy and fussy one still liked them then I’d have a win-win on this one at least.

Here is the finished recipe and YES the fussy one has been eating them all week…

5 oz butter
5 oz coconut oil
4 oz light muscovado or soft light brown sugar
2 tbsp maple syrup
1 tsp vanilla extract
3 oz ground almonds
1-2 tbsp chia seeds
2 oz milled seed (I use Aldi milled linseed, sunflower seeds and blueberry seeds)
10 oz oats


  1. Preheat the oven to 180oC and line a Swiss roll tin or baking tray (approx. 25 x 38cm) with baking parchment.
  2. Place the butter, coconut oil, sugar, maple syrup and vanilla extract into a medium sized pot and place over a medium heat, stirring frequently until the butter and coconut oil have melted and all ingredients are well mixed.
  3. Place ground almonds, chia seeds, milled seeds and oats into a large bowl, mix and then add the melted butter mixture.
  4. Mix well then pour into the prepared tin and spread out evenly.
  5. Bake in the oven for 15 minutes.
  6. Allow to cool then cut into squares.
  7. Enjoy!
Tasty and healthy - a winning combination
Tasty and healthy – a winning combination
Although I have spoken about the positive side to butter in a previous blog, I do hold with everything in moderation!  I am happy to replace some of the butter called for in the original recipe with Coconut oil as it is great for brain function, has antibacterial, antiviral and antifungal benefits and can help to reduce skin problems such as eczema.  The maple syrup replacing some of the sugar contains maganese and zinc which help boost the immune system.    The milled seeds and chia are high in vitamins, minerals and fibre as well as omega 3 fatty acids.  Not a bad addition to the lunchbox I think!


Now I have to work out what else to put into the lunchbox… has anyone else this lunchbox dilemma with a fussy child? My little one won’t eat sandwiches, fruit, dairy for snacks.  If anyone has any suggestions or comments please let me know!

Can you name this creature?

Week 2nd to 8th September 2013

A few people got this week’s Mystery Creature right, how did you do? It is the olinguito (Bassaricyon neblina).

photo credit: 禁书网中国禁闻 via photopin cc

This cute little creature is the first carnivorous mammal to be discovered in the Western Hemisphere in the last 35 years.  However they have not been hiding out on us, they have been on display in museums and some zoos for the decades.  The problem is that they were simply mislabeled, thought to be Olingos (a cousin that although similar is larger, with a shorter tail, bigger ears and a longer snout).

Residing in the cloud forests of the Andes this mammal is the smallest member of the racoon family. This arboreal, nocturnal creature is referred to as a carnivore, although fruit makes up most of it’s diet.

The scientific name given to this mammal is “Bassaricyon neblina” where nebulina means cloud and refers to the cloud forests where the olinguito (little Olingo) live.