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 this experiment, 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 (world book, 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, P 52). 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 energy drink that kick starts your day. Have you ever wondered, when you get called away and have already started making your hot drink, whether to put the milk in then or wait until you get back. To keep your drink as hot 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 at home and take-away. Some of these are: Glasses Mugs Enamel Cup Plastic cup Plastic disposable Polystyrene

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 hot drink make it cool quicker or slower? All these questions will be answered throughout this case study, with the explanations and data. 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.

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

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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 could be got hold of easily. Apparatus: 2 china mugs 2 thermometers 1 stopwatch Measuring cup Measuring spoons Kettle Milo International Roast Coffee Tuckfields ty-nee tips tea bags Milk Water

Materials:

Method
1. 2. 1 teabag. 3. 4. 5. 6. 7. 8. 9. 10. Boil the kettle with the same amount of water in it for each experiment (2litres) Put the 2 thermometers in the mugs and prepare 50mls of milk. (see fig. 2) When the kettle has boiled pour 200mls of water into each mug. Now in 1 mug put in the 50mls of milk. Record their max temperature (before they cool down) and let them sit for 5 minutes. 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. Do another one of these experiments for 10 minutes. Repeat this experiment for the 2 other types of drinks. Collect 2 of the same kind of mug. Put in each either 2 teaspoons of Milo, 1 teaspoons of coffee, or

When recording the final temperatures, record the temperature of the drink that has no milk, add the milk in, and record the other drinks temperature. Wait until the temperature of the 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 other experiment because ti showed how the drink that didnt have milk drop in temperature when eventually milk went in. I chose this method because it seemed like a good way to test and show what I was trying to find out.
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2 pieces of equipment that would have been useful is a more accurate thermometer and a kettle 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 10 minutes. It also shows the drop in temperature when milk is added in a drink at the end of 5 and 10 minutes. The key for the graph: 5 minutes Cup with milkCup without milk 10 minutes Cup with milkCup 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 drink then 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 drink that 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 tem than the drink that has not got milk in it. Things cool quicker the greater the difference is between their temperature and room temp so by the time the experiment is up the drinks are close in temperature, because the drink without milk was much hotter than the one with milk. When the milk is added to the hot drink without milk it cools down past the hot drink 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. The drink that has no milk in is dark therefore it is a better radiator of heat than the rink with milk 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 put the milk in the drink it will cool down even further and be cooler than if you had have put the milk in the first place. My hypothesis was correct, and I did not have many implications throughout this experiment. Some improvements that could have been made would only be very minor. They would include, more accurate thermometers, which took more accurate temperatures. Also somehow pouring hot water into the drinks at the same time other than one by one but at still 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 they would fall at the same rate. This experiment could also be conducted with different types of cups or more types of drinks.

Conclusion
My conclusion is if you want to keep your hot drink as warm as possible while you are away, 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?

Apparatus and materials

The apparatus and materials that were used to conduct this experiment are pretty basic and 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 Milo International Roast Coffee Tuckfields ty-nee tips tea bags Water Sticky tape

Materials:

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Method
Collect different types of containers: Mug Polystyrene Glass Plastic Disposable Plastic Cup Cup Enamel 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 (2 litres) and then either, in all of the containers put (2 teaspoons Milo, I teaspoons coffee, 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 before cooling down. 7. Repeat experiment 3 times with each type of drink When putting the thermometer in the containers they are unbalanced. Sticky tape the top of 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 record the 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 was trying 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 are limited with how you can do it. A bit of equipment that would have been useful is a thermometer that takes a temperature when you want it to over a period of time. Also, a stand that holds thermometers up, so I didn't have to use sticky tape.

Results
The results that I have collected have been carefully put into graphs, as shown in (Fig 8, 9 and 10). These graphs show, for each kind of drink, how hot each container keeps them. You can really 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 container fell, 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.
Mug Polystyrene Glass Plastic dis Cup Enamel Tea 27 31.3 22 32.7 25 34.7 Coffee 27.3 31.4 23.7 33 23.3 24.3 Milo 21.6 29.6 21.7 23.7 22.6 33 Average 25.3 30.7 22.4 32.8 23.6 34

Discussion
In this experiment I found out which drink container kept hot drinks at a slower cooling rate, and which ones didn't. Over all the 3 drinks glass kept them the hottest, only dropping an average over all the types 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 and gets 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 heat very well. It does not absorb much heat from the hot drink so, the drink stays hotter for longer. Enamel has a high heat resistance (Morgan 1994, p.26) so it conducts heat well. When the hot 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 also has a low resistance to heat. That explains why they are also are some of the top insulators. Also another reason I think is that polystyrene and other lower ones started off at a very high 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 the right place. This experiment went well with little implications.

Conclusion
My conclusion is that glass holds the best temperature followed by the below, and enamel holds the worst temperature. The following drinks, from top to bottom, have a slower cooling rate when they had hot drinks 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.

Apparatus and materials

The apparatus and materials that were used to carry out this experiment were very basic and would be easily gotten hold of. Apparatus: 7 mugs 7 thermometers Kettle Measuring cup Measuring spoons Stopwatch Milo International Roast Coffee Tuckfields ty-nee tips tea bags Milk Water

Materials:

Method
1. 2. 3. 4. 5. 6. 7. 8. 9. Boil kettle with the same amount of water in it for each experiment (2 litres). Prepare 6 mugs, that are the same. Place 2 teaspoons of Milo in 2 mugs and in 1 of them add 50mls of milk. Place 1 teaspoons of coffee in two of the mugs and In one of them add 50mls of milk. Place 1 teabag in each of the 2 mugs, and in 1 add 50mls of milk. Put a thermometer in each mug. When the kettle is boiled pour 200mls of water in each mug, stir, and start timing. Record the temperatures of each drink every minute. For 0 minutes record the max temperature that the drink gets before it starts cooling down. Repeat this experiment 3 times then average your results.

When measuring the amount of Milo and coffee use proper teaspoon measures, so it is easy to get an accurate measurement. Use the same thing that is used to measure something, 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 this experiment, without really good equipment to use. Apparatus that would have been great to use would be a thefl1lometer that could take a recording 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 and ones 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 a considerable difference at the start. Where the milk drink was cooler by an average of 11.4c. This margin dropped considerably and when 5 minutes had passed, the difference between milk and no milk was an average of -8.47c. The difference had dropped nearly 3 c in 5 minutes. By the time 10 minutes had gone the difference between black (ones without milk) and white (ones with milk) drinks was an average 6.1c. The difference had dropped an extra 2.30. Over the 30 minutes of the experiment the black drinks dropped an average of 27c and the white drinks dropped an average 18.4c. The black drinks cool .9c faster every 3 minutes than the white hot drinks do. The reason for the hot drinks without milk having a faster cooling rate than the hot drinks with 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 as much difference between its temperature and room temp. However the temperature of the hot 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 radiator of heat as the drink with no milk. The black drink is a faster radiator so therefore will cool down 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 hot drink without milk. My hypothesis was correct and this experiment had little implications and doesn't need very much improvement. Probably only better thermometers, just the technology side of things.

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Conclusion
My conclusion is that Hot drinks with milk, or white hot drinks, have a slower cooling rate than 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 go away 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 the slowest 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 than one with no milk in it. My final big conclusion is if you want to keep your drink hotter for longer, put it in a glass drink container and drink it with milk, if you are having it straight away, if not put the milk in before you go away. Enjoy your hot drinks!

References
1) Morgan, Sally and Morgan, Adrian Designs in science MATERIALS Evans Brothers Limited, London First published 1994 2) World Book Encyclopaedia, Books ci -cz and T Printed in USA First published in 1992 3) www.nescafe.com 4) Hewitt, P.G (1993) next-time Questions to accompany conceptual physics Harper Collins: New York

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