The Temperature and a Thermometer

1. Temperature: When things like water or air get heat, they start to get warm, and if they get a lot of heat, they become hot. We usually put our hand or finger in the water to judge how hot it is, but that is not an accurate measure. Besides, if the substance is very hot, we could get scalded. 
2. Thermometer: Instead of touching something hot, we use a thermometer. A thermometer is a tool that tells us exactly how hot or cold something is. The temperature on a thermometer is measured in degrees Celsius (°C), which is a way to quantify how hot or cold something is. 

Thermometer

Types of Thermometers:

1. Traditional Thermometers: Older thermometers have mercury inside them, which moves up and down a tube to show the temperature. But these are used less often now because mercury is dangerous if it breaks out.
2. Digital Thermometers: Today, most thermometers are digital. They show the temperature on a small screen and are safer and quicker to use.

1. Aim: To determine the temperature of various substances using a mercury thermometer and understand how the temperature affects the mercury level.

2. Requirements: mercury thermometer, vessel with hot water, vessel with cold water or ice.

3. Procedure

• Take a mercury thermometer and observe the mercury column in the capillary tube, noting its position on the scale.
• To measure air temperature, read the temperature corresponding to the mercury level at the thermometer's bulb.
• For water temperature, immerse the thermometer bulb completely in room-temperature water and note the mercury level.
• Place the thermometer in a vessel of hot water, submerge the bulb fully, and record the temperature shown.
• Repeat the process with a vessel of cold water or ice, ensuring the bulb is submerged, and record the temperature.

4. Observations: Note the different temperatures recorded: in air, in room temperature water, in hot water, and in cold water or ice. Observe how the mercury level changes with the temperature.

5. Conclusion: The experiment shows the responsiveness of mercury in the thermometer to changes in temperature, indicated by the rise or fall of the mercury level in the capillary tube when exposed to different temperatures.

Recording the temperature

1. Aim: To demonstrate how temperature perception is relative and cannot be accurately determined by touch.

2. Requirements: three similar vessels (labelled A, B, and C), hot water (for vessel A), cold water (for vessel B), and water at room temperature (mixed from A and B for vessel C).

3. Procedure

• Fill vessel A with hot water and vessel B with cold water.
• Mix some water from A and B into vessel C to make room-temperature water.
• Dip your right hand in vessel A (hot water) and your left hand in vessel B (cold water).
• Keep both hands immersed for 2-3 minutes.
• After 2-3 minutes, simultaneously dip both hands into vessel C (room-temperature water).
• Observe how each hand feels in the same water of vessel C.

4. Observation: The right hand (from hot water) feels the water in vessel C as cold. The left hand (from cold water) feels the water in vessel C as hot.

5. Conclusion: Temperature perception is relative and depends on the prior experience of the skin with different temperatures. This experiment shows that our sense of touch is not reliable for measuring temperature, emphasising the need for a device like a thermometer for accurate temperature measurement.

Relative sensation

Temperature is a parameter which tells the thermal state of a body (i.e., the degree of hotness or coldness of the body). It determines the direction of flow of heat when two bodies at different temperatures are placed in contact.

• If no heat flows between two bodies in contact, they are said to be at the same temperature, even though their thermal energies may be different.
• The S.I. unit of temperature is kelvin (K), and absolute zero (0 K) is the temperature at which molecular motion ceases.