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Does the temperature of the Onion affect the production of tears?

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Ge Am

on 18 March 2014

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Transcript of Does the temperature of the Onion affect the production of tears?

Does the temperature of the Onion affect the production of tears?
What happens when you cut an onion?
When you cut an onion, you are breaking cells. The gas inside the onion is released and they begin to mix producing propanethiol s-oxide. The gas reacts with the water in your eyes to form sulfuric acid and creating a chemical reaction. The sulfuric acid burns, stimulating your eyes to release tears to wash the irritant away.

Onion 1
Onion 3
This onion was hot. We heated up the onion for 60 seconds (using high level) and timed it just like the other onions. This onion only took us 26 seconds for us to start crying!
Onion 4
This onion was cool. We prepared the onion by putting it in the fridge over night to cool. We then did the same as before and sliced the onion into eighths. We reached the limit of 3 minutes and we weren't crying however, our eyes were still stingy and irritated.
Onion 5
This onion was freezing. We could barely cut it! We reached the maximum limit of 3 minutes again however this time, our eyes were almost not stingy and irritated.
Our hypothesis for this experiment proved to be true as the temperature of an onion does affect the production of your tears. We were pleased to find that the frozen onion had the least affect like we predicted as the onion cells froze and were unable to release gas. We were quite surprised when we witnessed the experimenting of the hot onion as it had the most effect. We thought that heating an onion would deactivate the enzymes because that is what happens when an onion is cooked. What we now think actually happened is that the heat wasn't enough to melt the acid but instead heat it so when cut the onion, the process sped up as hot gas rises.

Onion 2
This onion was warm. Our group heated this onion up for 30 seconds in the microwave (using high level) to reach the right temperature. We did the same as before to ensure it was a fair test. This onion took us 37 seconds for us to start crying.
This onion was in room temperature. We started the timer just before we started slicing the onion into eighths. It took us 1 minute and 16 seconds for us to start crying.
Our hypothesis was...
If the onion is frozen, then we predict that our eyes will not sting and get teary because the cells will be frozen, so the substances inside won't be able to release and mix.
We hope you have enjoyed the presentation and learnt a lot about onions and the reason behind your crying. Other ways to prevent your eyes from stinging are using a fan (to blow the gas away), cutting the onion underwater (to trap the gas inside the water) or simply by cooking the onion itself (to 'deactivate' the cells).

5 Onions
1 Microwave
1 Fridge/ Freezer
1 Knife
1 Chopping Board
1 Timer
5 onions were used in this experiment. All of them which sat at different temperatures ranging from hot, warm, room temperature, cool and freezing. The aim was to slice the onions into eighths and time how long it took us to cry within a time range of 3 minutes.
Independent: Temperature of the onion (time it was heated/ cooled)

Dependent: Time it takes for our eyes to start watering

Similar size onion
Same distance when cutting
Same person cutting
Same knife
Same cutting method

Our Results
Full transcript