Lab Report: The Effect of Adding Milk to Coffee on Temperature

Categories: Chemistry


When adding milk to hot coffee, the final temperature of the mixture can be influenced by the timing of adding the milk. In this experiment, we investigated the relationship between the time at which milk is added and the final temperature of the coffee/milk mixture. The hypothesis was that adding milk early would result in a cooler final temperature compared to adding it later. To test this hypothesis, we recorded the temperatures of hot coffee and cold milk at various time intervals and mixed them to observe the final temperature.

The results showed that adding milk earlier indeed resulted in a cooler final temperature, supporting the hypothesis.


Imagine it's a Saturday afternoon, and you've just brewed a fresh cup of coffee. You're about to add cold milk to it when the doorbell rings, and your friend needs your help. To ensure that you can enjoy your coffee as hot as possible after helping your friend, you might wonder whether it's smarter to add the milk now or after you return.

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Does the timing of adding milk make any difference?

The hypothesis is that adding milk after returning would be better, as hot coffee without milk would retain its temperature longer than warm coffee with milk. The aim of this experiment is to investigate the relationship between the timing of milk addition and the final temperature of the coffee/milk mixture.


Independent Variable: Timing of milk addition

Dependent Variable: Final temperature of the coffee/milk mixture

Controlled Variables:

  • Initial temperature of hot coffee/water
  • Initial temperature of cold milk
  • Volume of hot coffee/water (200 ml)
  • Volume of cold milk (50 ml)
  • Room temperature
  • Equipment used

Materials and Methods


  1. 250 ml beaker
  2. 50 ml beaker
  3. 100 ml measuring cylinder
  4. 50 ml measuring cylinder
  5. Thermometer
  6. Kettle
  7. Water cooler
  8. Stopwatch
  9. Stirring rod


  1. Take two test tubes.

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  2. In the first test tube, put cold milk (50 ml).
  3. In the second test tube, put hot coffee/hot water (200 ml).
  4. Place thermometers into both test tubes.
  5. Measure and record the temperature every minute for several minutes.

Data Collection

At the start of the experiment, the temperature of the hot coffee/water was 80.9°C. Over time, it cooled gradually, as shown in the table below:

Time (min) Temperature of Hot Coffee/Water (°C)
0 80.9
1 79.9
2 73.7
3 71.7
4 65.3

The temperature of the cold milk was 19.8°C and increased slightly over time:

Time (min) Temperature of Cold Milk (°C)
0 19.8
1 19.9
2 20.1
3 20.1
4 20.1

The final temperature when the milk and hot coffee were mixed together was 50.3°C.

Data Analysis

From the data collected, we can create a table to visualize the relationship between time and temperature for both the hot coffee/water and the cold milk.


Time (min) Temperature of Hot Coffee/Water (°C) Temperature of Cold Milk (°C) Temperature of Mixture (°C)
0 80.9 19.8 53.1
1 79.9 19.9 52.1
2 73.7 20.1 51.0
3 71.7 20.1 51.0
4 65.3 20.1 50.3

The table illustrates how the temperature of the mixture decreases over time as the hot coffee and cold milk are combined.


In this experiment, we aimed to determine the effect of the timing of milk addition on the final temperature of a coffee/milk mixture. The data collected and analyzed show that adding milk earlier results in a cooler final temperature. This supports the hypothesis that hot coffee without milk cools more slowly than warm coffee with milk.

However, it's important to note that this experiment had some limitations. We used only one metal rod to stir the coffee and milk, which may have affected the results as the rod was initially hot from stirring the hot coffee. Additionally, we used only one thermometer, and the temperature of the milk was measured immediately after mixing with the hot coffee, possibly leading to inaccuracies.

To improve the experiment, we could use two metal rods to ensure there is no residual heat transfer. We should also use two thermometers to measure the temperatures separately and more accurately. These improvements would enhance the reliability of the results.


Based on this experiment, it is recommended to add milk to coffee later if you want to keep your coffee as hot as possible. The experiment also highlights the importance of using appropriate equipment and controls to obtain accurate results. Further investigations could explore other factors that affect the cooling rate of coffee and milk mixtures, such as the initial temperatures of both substances or the type of milk used.

Updated: Dec 29, 2023
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Lab Report: The Effect of Adding Milk to Coffee on Temperature. (2016, Apr 05). Retrieved from

Lab Report: The Effect of Adding Milk to Coffee on Temperature essay
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