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The digestive system

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Today we looked at the human digestive system. We watched a short animation that helped us see how food travels through you body and what it does. We then had a sheet where we had to label the organs/parts of the digestive system.

 

Then we undertook an experiment to help us understand it.

In our pairs we started off with a plastic cup and fork. Miss Nicholson gave us food to mash. The fork demonstrated how teeth grinds up the food in the mouth. We were given banana, coco pops, cracker, crisps and sweetcorn. We mashed this all up then added water to represent the saliva. Saliva is a special chemical called enzymes which do the real work of breaking up the food and lubricates it so that it can be swallowed.

Once we made this watery past we swallowed the food down our esophagus (food tube) by emptying the cup into a sealed bag which was our stomach. Miss Nicholson came around with vinegar which was the stomach acid and we mashed our food some more to show the muscular contractions churning the food and mixing it with the digestive juices. Did you know that food can remain in the stomach for 3-4 hours.

After this process we emptied the contents of our stomach into a pair of tights, this represented our intestines. Digestion takes place in the small intestines. We showed this by squeezing the tights which took all the juices out. This was the nutrients we need for growth and energy leaving the intestines and flowing into the body. Food can be in the small intestines for 3 hours.

The food that we cannot digest along with bacteria turns into waste and passses into the large intestines, this was what was left at the bottom of the tights. The large intestines reabsorbs water in the blood and forms solid faeces. This can stay here for 18 hours upto 2 days! The waste is stored in the rectum until it is passed out of the body.

Did you know in your lifetime, your digestive system may have to process 50 tonnes of food! Now that’s a lot of food!!

 

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Tottie experiment

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After undertaking the hand washing experiment last week and discussing the importance of why we wash our hands we decided to undertake another experiment as germs can be found everywhere, but some places have more germs than others. So this this experiment was used to see where germs are hidden.

This is what we did:

  • Miss Nicholson washed her hands, put gloves on and then cut a tottie into five equal pieces.
  • We took the first tottie piece and put it in a bag and sealed the bag. We used the marker to write on the bag and labelled this bag as our ‘control’. This is so that we can see what would happen to a tottie without anyone or anything touching it to be able to compare the others with it at the end of the experiment.
  • We then picked a surface, we decided on the classroom floor. Whilst wearing gloves we took a second piece of tottie and rubbed it on the floor. After this we placed the piece of tottie in a different bag, sealed it and labelled it with classroom floor.
  • We took the third tottie piece outside and lay it in a dirty puddle before placing it in a different bag and labelled it with outside after sealing the bag.
  • The fourth bit of tottie was passed around peoples bare hands but since we had washed our hands after the glitter experiment we thought we would rub the tottie on our arms as well as our hands. We then placed this tottie in a bag with a label ‘hands’
  • For the final bit of tottie we decided to rub this on the toilet! We placed this in a bag, sealed it and labelled toilet.
  • We then took all five bags and place them in a dark cupboard at room temperature in the classroom. We left them for a week.

After we put these away we wrote up what we did and our predictions as to what we thought would happen to the totties.

After the week had passed we pulled the bags out of the cupboard and look at the potato pieces. This is what we found:

  • The control tottie had a little white mould on it but hadn’t changed much.
  • The tottie that was rubbed on the classroom floor was brown with a little more white mould on it.
  • The tottie that was outside in a puddle was dirty, a little bendy and had more more mould starting around the edge. It had a bit of a skin on it so when you bent it the skin broke a little.
  • The tottie that was rubbed in the toilet went brown and had a skin on it. It was really quite bendy and when you bent it the skin started to crack and come off.
  • The tottie that everyone touched with their bare hands…had the biggest difference! It was squishy and had juice coming out of it. It smelt really bad too!!!

Once we looked at the totties we discussed the germs that are called mould or bacteria. The number of germs has grown so much that we didn’t need a microscope to see them. The mould that we could see on the control is important because it shows us how many germs already existed there. The other pieces started with this many germs but once they had touched other things the tottie picked up more germs.

After our discussion we wrote up our results and discussed whether our predictions were right, close or not what actually happened. The older pupils were really good at supporting the younger pupils.

We then started making posters to remember to wash our hands so that we can put these up around the school.

School

Germ Science – How Clean Are Your Hands?

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On Tuesday we were learning the importance of hand washing and how to describe that germs may be present even if they are not seen.

Whatever we do, we come into contact with germs. It’s easy for a germ on your hand to end up in your mouth.Washing your hands is the best way to stop germs from spreading.

We think some of the best times to wash your hands are:

  • When your hands are dirty.
  • Before eating or touching food you are helping cook.
  • After using the bathroom.
  • After blowing your nose or coughing.
  • After touching pets or other animals.
  • After playing outside.
  • Before and after visiting a sick relative or friend.

We undertook an experiment to show the importance of why we should wash our hands. Here is the steps for this experiment:

  • 1. Put a drop of lotion on your hands and rub them together to spread the lotion out evenly.
  • 2. With your hands over newspaper, ask your partner to put a pinch of glitter in the palm of one of your hands.
  • 3. With your hands still over the newspaper, make a fist with the hand that has glitter on it, then spread your fingers out. (We had to say what we saw)
  • 4. Now press the palms of your hands together and pull them apart. (We then had to look at our hands and notice what happened)
  • 5. Touch your partner’s hand. (We noticed that the glitter moved onto our partners hands)
  • 6. Get a paper towel and use it to wipe your hands clean of all the glitter. (the paper towel only took some of the glitter off but it didn’t take it all off)
  • 7. After using the paper towel, try using soap and water to wash your hands. (After thoroughly washing our hands the glitter did come off – some of us had to go back and wash our hands again as we noticed one or two bits of glitter in between our fingers)

The glitter was acting the same way that the germs on our hands act. There are a lot of germs, they spread around easily, and it can be hard to get them off. The difference between the glitter and germs is that germs are so small you can’t see them without a microscope. You have to know when you may have come into contact with germs and then wash your hands.

If we accidently touched our mouth, nose, or eyes while doing this experiment, we may have found glitter getting left behind. Germs travel the same way and can easily enter our body if we touch our face with dirty hands and germs can make us sick. That’s why it’s important to wash our hands before we eat. It is also important to wash our hands after touching something that might have germs, such as when we use the bathroom or play outside. If we don’t, the germs can easily spread to more places and to other people and cause sickness.

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P4 -7 Science experiments

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On Monday primary 4-7 undertook various experiments about ‘changes’ as this is our topic this term.  Here are some of our experiments:

We have placed a white flower into water, with food colouring added in, to see if this changes the colour of the petals. Flowers absorb water through the xylem, which is a tissue of thin tubes found inside the stem. Water is transported to the various parts of the plant including the flower. Because the water is coloured the petals should then take on the colour.

It has been 2 days and the flower in the green water has begun to turn green but there isn’t much change with the other flowers yet. Some of us thought the flower would change within: 5 minutes, 20 minutes, 1 hour or 1 day but we were all wrong with our hypothesis.

We split the stem of a rose into 3 and placed each of these in a different colour, red, blue and yellow, to see if this will give us a rainbow rose.

This hasn’t really changed yet but we know with the other flowers that it could take a while.

 

We placed eggs into different liquids to see if/how this changes the egg. We have one in water as a control, one is in coke, another in vinegar and the last in fresh orange juice. We discussed our hypothesis on what we thought would happen to each egg:

  • The water wouldn’t change the egg
  • The coke would dissolve the shell and make it bounce
  • The orange juice wouldn’t do anything
  • Some thought the vinegar would dissolve the shell and make it bouncy

As soon as we put the egg in the vinegar it started to react by producing lots of bubbles, this is because the calcium carbonate in the shell is dissolved by the acetic acid producing carbon dioxide.

We checked the eggs after 1 day and there were slight changes:

  • The water had cracked the egg and it began to seep out
  • The coke hadn’t dissolved very little
  • The orange juice had dissolved quite a lot which was surprising
  • The vinegar had dissolved lots and made the egg squishy and bouncy

We checked the eggs again today and it was very interesting:

  • The water hadn’t changed from the day before, it was still split but nothing more has come out
  • The coke had dissolved very little but had stained the egg further
  • The orange juice dissolved the shell a little more
  • The vinegar had made the egg even bigger and bouncier

Below are close ups of the control, orange juice and coke

As you can see the egg in the vinegar is much bigger than the control egg in the water. This is because the membrane around the egg is semi permeable. Whilst it was in the vinegar the liquid moved through the membrane into the egg resulting in the membrane swelling and increasing in size.

We tested how well the vinegar egg could bounce. It bounced from 10cm high so we went up to 20cm and it still bounced so we tried dropping it from 30cm…it didn’t bounce though.

 

We poured milk into a glass and added red bull. When we discussed what we thought would happen there were a few different thoughts:

  • it would curdle
  • it would separate
  • it would sink to the bottom

You can just about see from the photo there is a layer at the top of the glass. After 5 minutes of pouring in the red bull the acid in the Red Bull causes the protein  in the milk to separate. When the milk curdles, a chemical reaction takes place resulting in a precipitate.

 

We did one more experiment with milk. We placed enough milk on a plate to cover the bottom. Then we poured drops of food colouring into the milk but nothing happened. We then took a cocktail stick and placed one end in fairy liquid before placing this into the milk and food colouring. What happened next was really cool.

The colours began to spread away from the fairy liquid and began mixing together. This is because fat and protein molecules in the milk are altered by the soap. These fat and proteins are super sensitive to change in the milk so when the fairy liquid is added it creates a chemical reaction and causes them to roll around. Once the soap molecules have mixed evenly with the fat and protein molecules the motion stops so we added more fairy liquid to keep the action moving. The food colouring helps us to see this change.