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Measurement at home

How to take the hot mug challenge

How to determine the cooling rate of drinks in mugs?

  • How much variation is there in how long containers keep drinks warm for?​
  • How much effect does a lid have?​
  • Do drinks take the same time to cool from 60 to 50 °C as from 50 to 40 °C?
  • What does this experiment have to do with reducing the impact of heating houses upon climate change?​

Estimated time: depends on drinks containers – Mostly 30 minutes though some can take hours. No prior knowledge needed.

Download the worksheet

Download the table

Equipment required​

  • Hot drinks containers. Ideally including an identical pair – one with a lid​
  • Measuring jug​
  • Thermometer that works up to 100 °C​
  • A clock or timer
  • Paper to record results in a table


  • Hot water can scald, take extreme care​
  • Take care if handling a glass thermometer​
  • mop up spilt water immediately

How to

Watch the video, then follow the instructions.

  1. List your drinks containers in a results table (as in video). Download table here.
  2. Very carefully use the measuring jug to put 100 ml of boiled water into each container. If the water temperature in the container is less than 60 °C, empty and refill with new hot water. Put on any lids.​
  3. Measure room temperature.​
  4. Measure water temperature for each container about once a minute. Record the time when the temperature is 60 °C. Replace lids each time and don’t leave the thermometer in the container.
  5. Continue measuring water temperature about once a minute. Write down the time when the temperature is 50 °C.​
  6. Continue measure water temperature and write down the time when the temperature is 40 °C. Give the thermometer time to settle outside the water, then measuring the room temperature.​
  7. Calculate times each drinks container takes to cool from 60 °C to 50 °C  and from 50 °C  to 40 °C, and record values.
  8. Share your results with us using the form below on this webpage.

Thoughts, tips and information

SI measurement units​

  • Second (s) for time (and minute = 60 seconds)​
  • Kelvin (K) for temperature ​
  • Metre (m) as litre for volume m3​

Challenge topics​

Climate measurement, measurement science, thermal properties, insulation, maths

  • Which material keeps drinks hot best?​
  • How do lids affect the result?​
  • What is the coldest temperature the drink will ever reach?​

Enter your results

Please enter your results in the table below. You may enter as many results as you like THOUGH PLEASE REFRESH THIS PAGE BEFORE EACH NEW ENTRY. Each time you Submit, you will send us the information written in the cells below.

* These are optional – the name is so we could mention you in the end of week report and the postcode is to see where people are taking part. We won’t use this information for anything else.