How long would I have to microwave corn syrup to get it to the hard ball candy stage?
I have 0.3 kg of corn syrup at room temperature (294 K). The specific heat of corn syrup is [2.72 kJ/(kg K)][1]. I want to heat it up in a 1,000 W microwave until it reaches 394 K.
I know that
q=mcΔT
so
q = 0.3 kg * 2.72 kJ/(kg K) * 100 K
q = 81.6 kJ = 82 seconds in a 1,000 W (1 kJ/second) microwave.
From my experience, it takes longer than 82 seconds to heat up corn syrup that much.
How should I account for extraneous variables?
From Chris H's Answer: 82 seconds to raise the temperature + 111 seconds to boil off the water = 3 minutes, 13 seconds in a 1,000 Watt microwave.
Best Answer
A major factor to note is that to get the corn syrup to 394K you don't just have to heat it, you have to concentrate it by boiling off some of the water. You need to take into account the latent heat of vaporisation of water, about 2,260 kJ/kg in the temperature range of interest. It's easy to see that this can be a major factor.
Hard ball candy is 90% sugar (Wikipedia), while corn syrup is more like 76%. From your 300g you thus need to drive off 49g of water; that will take 111kJ in addition to raising the temperature, more than doubling the energy (and time) required
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Does corn syrup harden when heated?
Corn syrup will only harden if heated to a certain temperature, where the water evaporates and the main component of sugar is left. Left sitting in the pantry, corn syrup will not harden.How do you heat corn syrup?
Just put your candy thermometer in the pan and watch for it to rise to 300 degrees. It takes about 10 minutes from the time it starts to really boil. After it's reached 300 degrees, remove it from the heat and add whatever flavor you want, stirring constantly then add food coloring.At what temperature does corn syrup Harden?
The process of turning sugar into a hard, smooth, transparent confection involves heating a sugar/corn syrup/water solution to 300 \u2013 310\xb0 F.How do you make a hard ball of sugar?
The hard-ball stage of sugar is when heated sugar syrup reaches a thick consistency that holds its shape when cooled in cold water. If you pour melted sugar from the pan into cold water, you can form it into a ball that will not flatten on its own. This stage occurs between 250 and 266 degrees Fahrenheit.Easy Glass Candy 5 Minute - 3 Ingredient Recipe
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Answer 2
Honestly, I'd go the trial-and-error route with that if you are going to do this for practical applications (e.g. guesstimating how long you need to put your syrup in the microwave)
If you want to actually build an accurate mathematical model, some things you should be taking into account:
1000W is the nominal potency of the microwave, not exactly the amount of energy it gives off from the magnetron. You also have a loss of energy within the oven itself, as not all the energy emitted will reach and be absorbed by your object.
Furthermore, the penetration of the microwaves will account for uneven cooking depending on the surface area of your object and the surface area x volume ratio, so you might have to interrupt your process to mix the liquid to an even temperature of 394K, or have a surface temperature higher than the core temperature.
As warned in the comments, please be VERY careful when heating up liquids in the microwave. If you have glass or ceramic beads that you can put in the liquid to heat up, that's good.
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