Hot and Cold
The temperature of an object: It is the degree of hotness or coldness of an object.
Measuring Temperature
There are two types of thermometers i.e. clinical and laboratory thermometer.
Clinical and experiental thermometers are based on the Celsius scale of temperature and both are mercury thermometers.
The thermometer that measures our body temperature is called clinical thermometer.
A clinical thermometer is made up of a glass tube of uniform thickness.
The scale of the thermometer records the temperature in degree Celsius, generally, 35°C to 45° C, which is the range of human body temperature.
On average, the temperature of the human body is around 37°C.
How to use the clinical thermometer?
- Firstly, wash the thermometer with an antiseptic solution.
- Before taking the temperature the thermometer is given a few jerks to bring down the level of Mercury below 35oC.
- Then the thermometer is placed beneath the tongue for about a minute.
- Then you can take it out and observe the temperature reading on the thermometer.
Precautions when using a clinical thermometer
- Wash the thermometer before and after using it.
- Make sure the temperature of the thermometer is below 35oC before taking the temperature.
- Keep the thermometer straight in order to see the Mercury level precisely.
- It should always be held with care or it can break down. You should not touch the bulb of the thermometer at all.
Laboratory Thermometer
The laboratory thermometer is used for measuring the temperature in the science laboratory.
The range of a laboratory thermometer is generally from – 10 degree Celsius to 110 degree Celsius.
The laboratory thermometer should be held vertically while measuring temperature.
Precautions are taken when using a laboratory thermometer
- You should always follow the same precautions as that of the clinical thermometer.
- You should always hold the laboratory thermometer in a straight upright position without tilting it.
- The bulb of the thermometer should never touch the surface of the container in which the substance is kept.
Minimum-maximum thermometer: It is a thermometer used to measure the minimum and maximum temperature of the day by weather forecasters.
Digital thermometer: This type of thermometer does not contain Mercury. It directly displays the correct temperature on a display screen.
Transfer of Heat
The flow of heat always takes place from and hot object to a cold object.
Conduction: The process of flow of heat from a hot object to a cold object is called Conduction.
Conductors: The objects that can allow the heat to flow through them are called Conductors. For Example, metals such as copper and aluminum.
Insulators: The objects that do not allow the flow of heat from them are called Insulators. For Example, Wood and Plastic.
Convection: The transfer of heat in liquids and gases is called Convection.
Convection in Water: Water is a poor conductor of heat. So, due to this reason, it cannot transfer heat by conduction but it transfers heat by the process of convection.
Convection in Air: Air is a very poor conductor of heat, air transfers heat from its hotter parts to the colder parts by the process of convection.
Sea and Land Breezes: The blowing of sea breeze and land breeze in coastal areas is generally occurred due to the convection of heat in air.
Radiation: It is a process of transfer of heat in the form of waves. For Example, the sun's heat reaches the Earth’s surface through radiation.
The wind blowing from the sea towards the land is called Sea Breeze.
Land Breeze: The wind blowing from the land towards the sea is called the land breeze.
Kinds of Clothes We Wear in Summer and Winter
During hot summer days, people prefer to wear white clothes or light coloured clothes because light coloured clothes absorb less heat from the sun and hence, keep us cool and comfortable in hot weather.
In the cold winter days people prefer to wear dark clothes because the dark coloured clothes absorb more heat rays from the sun and keep us warm in winter season.
In the winter, we use woolen clothes. Wool is a poor conductor of heat. Moreover, there is air trapped in between the wool fibers. This air prevents the flow of heat from our body to cold surroundings. So, we feel warm.
