Welcome to day 5 of our Spectacular Summer Science series, so far this week we’ve made baking soda ice cubes, done some slipping and sliding, investigated our heart rate and been on a bug hunt with Twinkl.
We struggle a little with learning at home in our house, due to my three children having such different needs, which is why I love Science Sparks as we can all learn something from the same activity. The one thing we always do consistently is read together at night we I think is very important. However, I am hoping to so some educational activities most days over the holidays. Z has worked so hard at school this year that I want to keep up the progress he has made. S starts school in September and will be one of the oldest, she has super writing, but is not very confident trying to read yet, so I wanted to spend some time alone with her doing that as well. I know I’m not alone in this, LeapFrog found that 23% of parents plan to carry out educational activities at least one a day with their children. Hopefully this series over summer will be a help to some of those parents.
I spotted today that LeapFrog are running a summer school on their facebook page where they feature a fab learning idea every day. My favourite from this week is asking a child to write an invitation to a friend for a playdate as a reward. I know my 6 year old would love this, and perhaps even more so if it was an invite to me so we could both do an activity together. I will definitely be using the resource for inspiration this summer.
So, back to our summer science series. Right back when we first started Science Sparks, we made some pretty flowers to demonstrate transpiration. This activity worked for me first time with amazing results, but when I tried more recently it didn’t work at all.
My theory was that something must have changed in the food colouring, on further inspection I noticed they all said ‘natural colours’, so decided to try a non natural food colouring.
This is what happened.
You can see clearly that the flower on the right has turned blue, this is because it has sucked the blue water up through the stem and into the petals.
I don’t know what the natural dyes don’t work, perhaps the colour particles are too big to travel up the stem. Do you have any theories for us?
The reason this happens is because of something called the transpiration stream. This is the movement of water up the stem of a plant from root to leaf when water is lost from the plant due to evaporation occurring at the leaves. Firstly water is absorbed by the root and moves through root hair cells via the process of osmosis (we will look at this another day!). It then moves into the xylem vessel which is the tube that carries the water up the plant. Plants are not like us with pumping mechanism that pushes our blood around, so water moves up the vessel by adhesion (being attracted to the side of the vessel) and cohesion (water molecules being attracted to each other). Therefore when water evaporates from the top of the leaves it changes the pressure in the vessel and pulls up the column of water to replace the water lost.
The best way to consider this is to imagine you have a thick shake – the straw can’t carry the shake up it, but if you suck from the top, you change the pressure and force the shake up the straw. It moves in a column because the molecules are attracted to each other.
Last Updated on January 9, 2015 by Emma Vanstone
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