Fill the glass up with snow.
Place the thermometer in the glass filled with snow and take the temperature.
Write down the temperature on a piece of paper.
Bring the glass inside and wait until for about 5 minutes until the snow melts.
Now, take the temperature again. What happened?
The temperature of the snow was much colder than the temperature of the melted snow or water. Water freezes at 32 degrees. When the glass of snow was brought inside, the temperature indoors was much warmer than 32 degrees and melted the snow. This is how the melting process works!