Apologies for the double posts. My computer doesn’t seem to have changed to 2015 so posts keep being posted in 2014. Then I repost for the day it should have come out on ie today. I’ll attempt to get it sorted so I will only need to post once!
One of my biggest goals this academic year is to introduce a bit of hands on, fun science. This is a little treasure of a book. I’m so excited about this book, because it is chock full of non age dependent science activities. This means I should be able to do them with all 5 children. The demonstrations are interesting enough to hold my three-year old’s attention, easy enough for my six-year-old to do and challenging enough to make my older ones think about the reasons behind why certain things happen.
Over the past few days we have been having a little play, learning about straws and how they work.
Day 1: Make your own straw
We used a strip of paper. Securing the edge, we rolled the strip diagonally until we had a tube. We then secured the end:
We tried it out to see if it worked:
We found we had to suck much harder to get the water up compared to a normal straw and surmised it was due to the air gaps of the unsecured middle part of the straw.
Day 2: How do straws work?
Using bought straws, we sucked up a little water into the straw and then held our finger across the top of the straw:
We placed it over the beaker and removed our finger. The water remained inside the straw whilst the finger covered the top but once removed the water fell out into the beaker.
The finger at the top lowers the pressure exerted on the water inside the straw. The pressure underneath the straw is, by comparison, much stronger therefore holding the water inside the straw. Once the finger is removed, normal atmospheric pressure exerts a greater downward force than the pressure under the straw, so the water falls out into the beaker.
Day 3: Making a medicine dropper
Using the principles from the previous demonstration we practiced raising and lowering our finger over the top of the straw, until we were able to let the liquid out one drop at a time:
Day 4: Making a straw Atomizer
We attempted to make a straw atomizer. We cut a slit about a third the way down the straw and bent it over. Placing the smaller part of the straw in the beaker of water and keeping the slit about 1/4 inch above the surface of the water, we blew hard:
As our breath travels over the top of the short section it reduces the pressure directly above. This means the greater pressure exerted on the water underneath pushes the water up the short section of the straw. As it reaches the top the moving air from our breath blows it off in drops.
Day 5: Making a straw oboe
We made a straw Oboe. We squeezed the top end of the straw flat and snipped off two triangles to form wedges (or reeds). We practiced blowing through it without puckering up our lips. Next we snipped three holes further down the straw and practicing making different sounds by placing our fingers over the holes:
We found we could make different sounds depending how many holes we covered with our fingers:
As with a real oboe the reed flaps open and close at high-speed causing a start/stop air flow. This vibrating air makes sound. Covering holes lengthens the air column and determines the pitch of the sound. The shorter the air column, the faster the vibrations and the higher the note.
Day 6: Making a water trombone
We made a water trombone. We poured water into a beaker until it was 3/4 full. We put the straw in the water and blew across the top of the straw. We moved the beaker up and down to change the sound we made:
As we lowered the beaker the sound got lower. This is because we are lengthening the column of air in the straw, reducing its vibration speed and lowering its pitch.
Day 7: Bending a straw without touching it
We bent a straw without touching it. We filled up a see through conical flask and placed a straw inside. We looked at it from the top, sides and bottom. When we looked at the straw from the side of the glass, it appears to bend at the point where it enters the water:
Light travels slower through denser materials. Water is denser than air, so the light traveling from the part of the straw in the water to our eyes travels at a slower rate than the light rays travelling from the straw part in the air. This creates the illusion of a bent straw!
These are my kind of activities – simple, frugal and quick.
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