Question

Introduction

If a cup of cold water is mixed with a cup of hot water, the final temperature of the mixture will be between the two initial temperatures. Using information on the temperature and volume of the hot and the cold water, the final temperature of the mixture could be predicted. This virtual experiment involves mixing of equal volume of cold and hot water and prediction of the final temperature of the mixture.

Procedure

Step 1

To get equal volume of cold and hot water, first three small Styrofoam cups are marked equally at about the three-quarter level. You can do this by pouring water from one cup to the next and mark the level along the inside of each cup. This is to make the volume of water equal in all cases.

Step 2

About a liter of water is brought to boiling in the boiling pan. The first cup is filled to the mark with cold water from the tap. Then the second cup is filled with hot water from the pan to the same level, using a beaker or a larger Styrofoam cup for scooping. The temperature of both cups of water is measured in thermometer, and recorded in the blank space a) and b) below.

a)         Temperature of cold water = 20⁰C_____

            b)         Temperature of hot water = 82⁰C______

Step 3

Predicting the temperature of the water, when the two cups of different temperatures indicated above, are mixed. The two cups of water are poured into the larger Styrofoam, and the mixture is stirred slightly, and the temperature is measured and recorded (actual measured temperature value is given on b) below. Calculate the predicted value and enter it in the blank space below [on a)]. Note that the volume of both cold and hot water are equal.

1. Predicted or calculated temperature = ______________ (show calculation)
2. Actual or measured temperature = 46⁰C

If there is a difference between the calculated predicted value and the actual measured value, what may have caused it, if there is a difference? State it in the blank lines below.

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The mixture water is discarded into the sink and the following experiment is continued.

Step 4

One smaller cup is filled to its mark with cold water from the tap. Another two small cups are filled to their mark with hot water. The temperature of water in each cup is measured and recorded [shown on a), b), and c)] below.

Predicting the temperature of the water when the three cups are mixed. The three cups of water are poured into the larger Styrofoam cup, the mixture stirred slightly, and its temperature recorded [actual temperature value for the mixture is given on e)] below. Calculate and enter the predicted temperature value of the mixture and enter it in the blank space of d.

Note that the volume of water in all three cups are equal

1. Temperature of cold water: 20⁰C
2. Temperature of hot water (cup 1): 82⁰C_______________
3. Temperature of hot water (cup 2): 83⁰C_______________
4. Predicted or calculated temperature of mixture: _______________ (show calculation)
5. Actual temperature: 55⁰C

How is the actual temperature of the mixture compared with the calculated and predicted temperature value? If there is a difference, give possible explanations as to what might have caused it in the following blank space.

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Which of the water samples (cold or hot) changed more from the initial temperature, when it becomes part of the mixture? In terms of energy conservation, suggest a reason for why this happened.

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Step5

Two small cups are filled to their marks with cold water from the tap. The third cup is filled to its marks with hot water. The temperature of each was measured and recorded (a, b, c). Then the three cups of water are poured into the large Styrofoam cup, the mixture stirred slightly, and the temperature recorded (e). Calculate and predict the temperature of the mixture when the three cups of different temperature values given below are mixed and enter it in the blank line of (d).

1. Temperature of cold water (cup 1): 19⁰C
2. Temperature of cold water (cup 2): 21⁰C
3. Temperature of hot water: 85⁰C
4. Predicted or calculated temperature of mixture --------------------- (show calculation)
5. Actual temperature: 40⁰C

How is the observed or actual temperature value (e) compared with the predicted or calculated temperature value (d)? Give a possible explanation if there is a difference.

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Which of the water samples (cold or hot) changed more when it became part of the mixture? Suggest a reason for why this happened.

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What determines whether the equilibrium temperature of a mixture of two masses of water will be closer to the initially cold or hot water?

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Answer 1

Tm Tamat Tmi mitm) Where Ima temp of mixture T → temp. of 1st liquid MI mass of est Tax me) temp of and Here the mass of water in both are equal i.e. mz alow here I - temp. of and Case I mu - m (day) 20c Ir = 82 C then Im = com team Joem 2m 2m Im Temp of mixture 516 while the measured temp. is abc this difference occurs because the mixture T = 20c while masses of every cupis Same get colder time Case-II TL Is 82 C 83 C. 61.67°C Tm : 2oom t 82m +83m mtm tm Temp. of mixture will be some reason while we measuring mixture of water get time. the the the temp. by

here we can see easily that the sample of cold water change for more from it initial temp. from 20°c to this happens because the comount of cold werter is less mixture i'm the . Case-111 Ti = 19°C also here masses of all Cups T2 = 210 liquid are same let m Is = 85C. m blog) then temp of mixture (TM) mit mit mis 7tm tm) 1251 3. Same_explomation In this case the hot water Samples changed more from its initial tem. from 85C to 41.676 The amount of or . Say masses of cold or liquid determines that the mixture will have temp. closes to intially Cold as hot water
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