Final answer:
One way to determine if the outside temperature is higher or lower than 0 °C without a thermometer is by observing if water freezes. Another method is to monitor the rate of ice melting. Using a barometer can help predict changes in weather, but it does not directly measure temperature.
Step-by-step explanation:
One way to experimentally determine whether the outside temperature is higher or lower than 0 °C (32 °F) without using a thermometer is by observing if water freezes. Place a glass of water outside and if the temperature is below 0 °C, the water will freeze.
Another way is to monitor the rate of ice melting. If the outside temperature is above 0 °C, the ice will melt at a faster rate.
Using a barometer to assess air pressure might indicate a change in weather, but it does not directly determine the outside temperature.