Heat

Q22. What is clinical thermometer?

Ans. The thermometer that measures our body temperature is called a clinical thermometer.

Q23. Give two examples each of conductors and insulators of heat.

Ans.  Conductors – aluminum and copper

        Insulators - water and air

Q24. How does the heat travel in air?

Ans. The air near the heat source gets hot and rises. The air from the sides comes in to take its place. In this way the air gets heated.

Q25. What do you understand by heat?

Ans. Heat is a form of energy that can be transferred from one object to another or even created at the expense of the loss of other forms of energy.

Q26. What is the use of maximum-minimum thermometer?

Ans. The maximum and minimum temperatures of the previous day, reported in weather reports, are measured by maximum-minimum thermometer.

Q27. One litre of water at 30°C is mixed with one litre of water at 50°C. The temperature of the mixture will be

(a) 80°C            (b) more than 50°C but less than 80°C

(c) 20°C             (d) between 30°C and 50°C.

Ans. (d) between 30°C and 50°C.

Q28. Why does the mercury not fall or rise in a clinical thermometer when taken out of the mouth?

Ans. Clinical thermometer has kink near the bulb prevents mercury level from falling on its own.

Q29. Why clinical thermometer cannot be used to measure high temperatures?

Ans. Clinical thermometer cannot be used to measure high temperatures because the range of this thermometer is from 35°C to 42°C only.

Q30. Explain land breeze.

Ans. At night, the water cools down more slowly than the land. So, the cool air from the land moves towards the sea. This is called the land breeze.

Q31. What is the concern associated with the use of mercury thermometer?

Ans. There is a lot of concern over the use of mercury in thermometers. Mercury is a toxic substance and is very difficult to dispose of if a thermometer breaks.

Q32. Explain the construction of clinical thermometer.

Ans. A clinical thermometer consists of a long, narrow, uniform glass tube. It has a bulb at one end. This bulb contains mercury. Outside the bulb, a small shining thread of mercury can be seen.

Q33. In places of hot climate it is advised that the outer walls of houses be painted white. Explain.

Ans. In places of hot climate it is advised that the outer walls of houses be painted white because light color reflects most of the heat that falls on them and thus keep the house cool.

Q34. Is it possible to construct buildings that are not affected much by heat and cold outside?

Ans. This can be done by constructing outer walls of buildings so that they have trapped layers of air. One way of doing this is to use hollow bricks, which are available these days.

Q35. What do you mean by maximum-minimum thermometer?

Ans. Different types of thermometers are used for different purposes. The maximum and minimum temperatures of the previous day, reported in weather reports, are measured by a thermometer called the maximum - minimum thermometer.

Q36. Why clinical thermometers range from 35°C to 42°C?

Ans. The clinical thermometer is designed to measure the temperature of human body only. The temperature of human body normally does not go below 35°C or above 42°C. That is the reason that this thermometer has the range 35°C to 42°C.

Q37. Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing.

Ans. Wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing because air get trapped in between the layers of clothing and being a bad conductor of heat, prevents the flow of heat from our body to the cold surroundings.