cooling of hot drinks

7/30/2019 cooling of hot drinks

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Work sample

Introduction

Hot drinks are drunk by numerous people, every day, in the vast majority of countries.The most common are coffee, tea and malt drinks like Milo.

Tea: Tea is drunk all over the world and has a high source of antioxidants. In 1990,approximately 2.5 billion kg of dried tea was produced (world book, Book T P 77).There are many different brands of tea including the one I am using in thisexperiment, tuckfields ty-nee tips. Each Australian drinks about 1.4kg of tea a year(world book, Book T, P 77) and India produces 720 million kg each year (worldbook, Book T, P 77).

Coffee: Coffee is a popular drink that is enjoyed in most places. Coffee is grown all

over the world with Brazil producing 30% of it (world book, Book Ci-Cz, P52). Coffee contains caffeine so therefore can be used to be kept awake.

Milo: Milo is made by Nestle, but is only drunk in Australia. Milo is a popular malt energydrink that kick starts your day.

Have you ever wondered, when you get called away and have already started making yourhot drink, whether to put the milk in then or wait until you get back. To keep your drink ashot as possible.

You may not have, but this is an old question, which is often asked as the illustration in

figure 1 shows.

To take this matter even further. There are an awful lot of drinking containers, both athome and take-away. Some of these are:

Glasses Plastic cupMugs Plastic disposableEnamel PolystyreneCup

Which one should you use to keep your drink cooling the slowest.

What about the cooling rate of hot drinks, with and without milk. Does the milk in a hotdrink make it cool quicker or slower?

All these questions will be answered throughout this case study, with the explanations anddata.

The purpose of this case study is for 3 things:1. If you get called away, whether to put milk in your hot drink then or wait until you get

back.

2. Which drink containers keep hot drinks insulated the best without using milk.

Printed from the Learning, Teaching and Assessment Guide athttp://www.ltag.education.tas.gov.au 1
http://www.ltag.education.tas.gov.au/http://www.ltag.education.tas.gov.au/http://www.ltag.education.tas.gov.au/


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3. To find out if drinks have a slower cooling rate when they have milk or no milk inthem.

Printed from the Learning, Teaching and Assessment Guide at http://www.ltag.education.tas.gov.au 2


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Experiment 1

If you get called away, whether to put milk in you hot drink then or wait until you get back?

Apparatus and materials

The apparatus and materials that were used in this experiment were pretty basic and couldbe got hold of easily.

Apparatus: - 2 china mugs- 2 thermometers- 1 stopwatch- Measuring cup- Measuring spoons- Kettle

Materials: - Milo- International Roast Coffee- Tuckfields ty-nee tips tea bags- Milk- Water

Method1. Collect 2 of the same kind of mug.2. Put in each either 2 teaspoons of Milo, 1 teaspoons of coffee, or

1 teabag.

3. Boil the kettle with the same amount of water in it for eachexperiment (2litres)

4. Put the 2 thermometers in the mugs and prepare 50mls of milk.(see fig. 2)

5. When the kettle has boiled pour 200mls of water into each mug.6. Now in 1 mug put in the 50mls of milk.7. Record their max temperature (before they cool down) and let

them sit for 5 minutes.8. When 5 minutes is up record both temperatures then pour 50mls

of milk into the drink that doesnt have milk in it, and record the temperature.9. Do another one of these experiments for 10 minutes.10. Repeat this experiment for the 2 other types of drinks.

When recording the final temperatures, record the temperature of the drink that has nomilk, add the milk in, and record the other drinks temperature. Wait until the temperature ofthe drink that just got the milk added finishes dropping then record it to.

This experiment had a good method, which worked very well. It was as good as any otherexperiment because ti showed how the drink that didnt have milk drop in temperaturewhen eventually milk went in.

I chose this method because it seemed like a good way to test and show what I was tryingto find out.



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2 pieces of equipment that would have been useful is a more accurate thermometer and akettle that pours 2 cups at a time.

Fig 2.



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Results

My results consist of 3 graphs and a table.

The graphs show how far drinks with mild and drinks without, drop in temperature over 5

and 10 minutes. It also shows the drop of temperature when milk is added to a hot drink.

The table shows each type of drink, and the start and finish temperature for 5 and 10minutes. It also shows the drop in temperature when milk is added in a drink at the end of5 and 10 minutes.

The key for the graph: 5 minutes

Cup with milk- -

Cup without milk -

10 minutes

Cup with milk- -

Cup without milk -

Fig 3.



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Fig 4

.

Fig 5.



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Discussion

In this experiment I found out, if you get called away, whether to put milk in your hot drinkthen or wait until you get back.

The answer is put the milk in before you go to ensure your drink stays hotter for longer.

In the results I found out that, no matter what kind of drink or time period gone the drinkthat had milk in it straight away always was warmer at the end of the experiment.

The hot drink cool down when the milk is added, so its temperature is closer to room temthan the drink that has not got milk in it. Things cool quicker the greater the difference isbetween their temperature and room temp so by the time the experiment is up the drinksare close in temperature, because the drink without milk was much hotter than the onewith milk. When the milk is added to the hot drink without milk it cools down past the hotdrink that already had milk in it temperature (see fig 5).

Another reason is when the milk is added to the hot drink it lightens the colour of it. Thedrink that has no milk in is dark therefore it is a better radiator of heat than the rink withmilk in it. Being a better radiator of heat the hot drink will cool faster (Conceptual physics,chapter 15, a sheet that was given to me by miss Devitt). When you come back and putthe milk in the drink it will cool down even further and be cooler than if you had have putthe milk in the first place.

My hypothesis was correct, and I did not have many implications throughout thisexperiment.

Some improvements that could have been made would only be very minor. They wouldinclude, more accurate thermometers, which took more accurate temperatures. Alsosomehow pouring hot water into the drinks at the same time other than one by one but atstill keeping things accurate.

To take this experiment even further you could extend the time on which the cups sit for,but after a while the second cup would get down to the same temp as the first and theywould fall at the same rate. This experiment could also be conducted with different types ofcups or more types of drinks.

Conclusion

My conclusion is if you want to keep your hot drink as warm as possible while you areaway, put the milk in before you go.

Reasons for this conclusion have been discussed in my discussion.



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Experiment 2

Which containers keep hot drinks insulated the best without using milk?


The apparatus and materials that were used to conduct this experiment are pretty basicand there would be no problem of getting hold of them.

Apparatus: - 1 china mug- 1 polystyrene cup- 1 glass cup- 1 plastic disposable cup- 1 plastic reusable cup- 1 china cup- 1 enamel cup- 6 thermometers- Stopwatch- Kettle- Measuring cup- Measuring spoons

Materials: - Milo- International Roast Coffee- Tuckfields ty-nee tips tea bags- Water - Sticky tape



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Method

Collect different types of containers: MugPolystyreneGlassPlastic DisposablePlastic CupCupEnamel

2. Do all of the same type of drink first (tea, Milo, coffee), in each of

the different containers.3. Boil the kettle using the same amount of water in it each time (2litres) and then either, in all of the containers put (2 teaspoons Milo, I teaspoonscoffee, or 1 teabag).

4. Put a thermometer in each container. .5. When the kettle is boiled pour 250mls of water in each container,stir, and start recording every 2 minutes for 20 minutes. (See Fig 7)6. For 0 minutes record the top temperature the drink gets beforecooling down.7. Repeat experiment 3 times with each type of drink

When putting the thermometer in the containers they are unbalanced. Sticky tape the topof the thermometer to a wall and slip the container under them.

For 0 minutes record the top temperature the drink gets before cooling down.Repeat experiment 3 times with each type of drink

Use proper measuring teaspoons to keep things accurate and use a stopwatch to recordthe time.

Draw up a record sheet before starting to make it easy to record your results.



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I chose this method because it seemed like an accurate and easy way to test what I wastrying to find out.

This method was a good one and worked well, and I found out what I wanted to.

Again I don't think this method was any better than any other ones, it is just that you arelimited with how you can do it.

A bit of equipment that would have been useful is a thermometer that takes a temperaturewhen you want it to over a period of time. Also, a stand that holds thermometers up, so Ididn't have to use sticky tape.

Results

The results that I have collected have been carefully put into graphs, as shown in (Fig 8, 9and 10).

These graphs show, for each kind of drink, how hot each container keeps them. You canreally see that ones fall much steeper than others.

The key for the graph: Polystyrene -

Glass -

Cup -

Mug -

Enamel -

Plastic -

Plastic Dis -

There is also a table that shows how far the temperature of each drink, in each containerfell, including the average amount fallen for each kind of drink together.



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Fig 8.

Fig 9.



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Fig 10.

Fig 11.

Tea Coffee Milo Average

Mug 27 27.3 21.6 25.3

Polystyrene 31.3 31.4 29.6 30.7

Glass 22 23.7 21.7 22.4

Plastic dis 32.7 33 23.7 32.8

Cup 25 23.3 22.6 23.6Enamel 34.7 24.3 33 34

Discussion

In this experiment I found out which drink container kept hot drinks at a slower coolingrate, and which ones didn't.

Over all the 3 drinks glass kept them the hottest, only dropping an average over all thetypes of drinks of 22.4c (see Fig 11.), and enamel was the worst, dropping 34c

(see Fig II)

The results from the best insulator to the worst is: -Glass-Cup-Mug-Plastic-Polystyrene-Plastic disposable-Enamel

One of the reasons for these results is that different materials have low and high

resistance to heat. If something has a high resistance to heat it conducts heat well andgets hot quickly and the opposite for low heat resistance.



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Glass has a low heat resistance (Morgan 1994, p.28) so therefore does not conduct heatvery well. It does not absorb much heat from the hot drink so, the drink stays hotter forlonger.

Enamel has a high heat resistance (Morgan 1994, p.26) so it conducts heat well. When thehot drink is added it absorbs its heat which cools down the drink.

Ceramics such as the cup and mug are quite similar to glass (Morgan 1994, p.29) so alsohas a low resistance to heat. That explains why they are also are some of the topinsulators.

Also another reason I think is that polystyrene and other lower ones started off at a veryhigh temperature so they would fall quicker as I have proved in my other experiments.

It surprised me to see polystyrene so far down the result list. Probably because I hadn't

done any research then but I thought it would be one of the top insulators.

My hypothesis was fairly wrong, but in some places it was in the right order but not in theright place. This experiment went well with little implications.

Conclusion

My conclusion is that glass holds the best temperature followed by the below, and enamelholds the worst temperature.

The following drinks, from top to bottom, have a slower cooling rate when they had hotdrinks in them:

-Glass-Cup-Mug-Plastic-Polystyrene

-Plastic Disposable-Enamel.

Reasons for these results have been discussed in my discussion.



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Experiment 3

To find out if drinks have a slower cooling rate when they have milk or no milk in them.


The apparatus and materials that were used to carry out this experiment were very basicand would be easily gotten hold of.

Apparatus: - 7 mugs- 7 thermometers- Kettle- Measuring cup- Measuring spoons- Stopwatch

Materials: - Milo- International Roast Coffee- Tuckfields ty-nee tips tea bags- Milk- Water

Method

1. Boil kettle with the same amount of water in it for each experiment (2 litres).2. Prepare 6 mugs, that are the same.

3. Place 2 teaspoons of Milo in 2 mugs and in 1 of them add 50mls of milk.4. Place 1 teaspoons of coffee in two of the mugs and In one of them add 50mls of

milk.5. Place 1 teabag in each of the 2 mugs, and in 1 add 50mls of milk.6. Put a thermometer in each mug.7. When the kettle is boiled pour 200mls of water in each mug, stir, and start timing.8. Record the temperatures of each drink every minute. For 0 minutes record the max

temperature that the drink gets before it starts cooling down.9. Repeat this experiment 3 times then average your results.

When measuring the amount of Milo and coffee use proper teaspoon measures, so it iseasy to get an accurate measurement. Use the same thing that is used to measuresomething, again to avoid inaccurate results.

Use a stop watch to record the time.

Have a recording sheet already done so you don't lose track of results, (see fig 3)



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I chose this type of method because it seemed like an accurate way to do my experiment,with little fuss.

It was a good way to do it because every thing was the same. This method was not

necessarily better than others, it is just that there are not many ways you could do thisexperiment, without really good equipment to use.

Apparatus that would have been great to use would be a thefl1lometer that could take arecording every minute, so that the experiment would be even more accurate.

Results

The results that I have found out have been put together in a graph (Fig 12)The graph shows how the temperature of the hot drinks drop over time.

The key for the graph: Milo with milk -

Milo without -

Coffee with milk -

Coffee without -

Tea with milk -

Tea without -

Fig 12.



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Discussion

In this experiment I found out the different cooling rates of hot drinks with milk in them andones without.

Hot drinks with milk in them don't cool down as fast as hot drinks without milk.

For all results refer to (Fig 12.)

My results showed that between hot drinks with milk and ones with no milk, there was aconsiderable difference at the start. Where the milk drink was cooler by an average of11.4c. This margin dropped considerably and when 5 minutes had passed, the differencebetween milk and no milk was an average of -8.47c. The difference had dropped nearly3 c in 5 minutes.

By the time 10 minutes had gone the difference between black (ones without milk) andwhite (ones with milk) drinks was an average 6.1c. The difference had dropped an extra2.30.

Over the 30 minutes of the experiment the black drinks dropped an average of 27c andthe white drinks dropped an average 18.4c. The black drinks cool .9c faster every 3minutes than the white hot drinks do.

The reason for the hot drinks without milk having a faster cooling rate than the hot drinkswith milk is as follows:

Things cool faster, the greater their difference is compared to the room temperature.

When the milk is added to the hot drink, its temperature decreases and there is not asmuch difference between its temperature and room temp. However the temperature of thehot drink is very much higher than room temperature.

Also when milk is added to a hot drink it lightens the colour, so it is not as good a radiatorof heat as the drink with no milk. The black drink is a faster radiator so therefore will cooldown faster (Conceptual physics, chap 15, the sheet that miss Devitt gave me).

As a result of the above it is clear to see that a hot drink with milk cools slower than a hotdrink without milk.

My hypothesis was correct and this experiment had little implications and doesn't needvery much improvement. Probably only better thermometers, just the technology side ofthings.



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Conclusion

My conclusion is that Hot drinks with milk, or white hot drinks, have a slower cooling ratethan hot drinks without milk or black hot drinks.

Reason why have been discussed in my discussion.

The Big Conclusion

My conclusion for experiment 1 is if you want to keep your hot drink hotter when you goaway put the milk in before you go.

My conclusion for experiment 2 is use a glass cup when you have a hot drink to get theslowest cooling rate, to keep your drink hotter.

My conclusion for experiment 3 is that a hot drink with milk in it will cool down slower thanone with no milk in it.

My final big conclusion is if you want to keep your drink hotter for longer, put it in a glassdrink container and drink it with milk, if you are having it straight away, if not put the milk inbefore you go away.

Enjoy your hot drinks!

References

1) Morgan, Sally and Morgan, AdrianDesigns in science MATERIALSEvans Brothers Limited, LondonFirst published 1994

2) World Book Encyclopaedia, Books ci -cz and T

Printed in USAFirst published in 1992

3) www.nescafe.com

4) Hewitt, P.G (1993)next-time Questions to accompany conceptual physicsHarper Collins: New York

http://www.nescafe.com/http://www.nescafe.com/

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cooling of hot drinks