Which of the following types of thermometers can be used to measure a range of temperature from -50°C to 50°? i. Clinical ii. Mercury iii. Alcohol-in-glass

Step 1: Analyze the question We need a thermometer that can measure from -50°C to 50°C. The key limit is the liquid's freezing point, which sets the lowest temperature it can measure.

Step 2: Concept A liquid thermometer works only while its liquid stays liquid.

• Mercury freezes at about -39°C, so it cannot measure -50°C. It boils at about 357°C.
• Alcohol freezes at about -115°C (ethanol), so it can easily measure -50°C. It boils at about 78°C, which is well above 50°C.
• Clinical thermometer has a very narrow range, about 35°C to 42°C, designed for body temperature. It also has a constriction that holds the reading.

Step 3: Check each type

• i. Clinical: range is only about 35°C to 42°C. It cannot cover -50°C to 50°C. ✗
• ii. Mercury: freezes at -39°C, so it fails below that. ✗
• iii. Alcohol-in-glass: liquid from about -115°C to 78°C, so it covers -50°C to 50°C. ✓

Step 4: Answer Only the alcohol-in-glass thermometer works for the whole range, so it is iii only, which is option C.

Tip: Remember the freezing points: mercury is about -39°C, alcohol about -115°C. If a question involves very cold temperatures (below -39°C), choose alcohol. For very high temperatures (above 78°C), choose mercury.