Science 2 Marks Questions

In places of hot climate, it is advised to paint the outer walls of houses as white because a light colour such as white reflects back most of the heat that falls on it. Hence, a light colour tends to keep the house cool.

During winters, we prefer wearing more layers of clothing than just one thick piece of clothing because air gets trapped in between the various clothing layers. Being a poor conductor of heat, air prevents heat loss from our body. Hence, layers of clothing keep us warmer than a single layer

Since, the shiny surface absorbs very little heat due to which the reflectors reflect all the heat which makes the room heaters more effective. So, due to this reason, room heaters have shiny reflectors.

As a fact that warm air is much lighter than the cold air, so being heavier the cold air from air conditioner moves downwards while the hot air moves upwards at the lower level and gets cooled and come downwards once again. So, due to this convection of heat are set in the air and room gets warmer faster.

In between the layers of cloths there is trapped air. As air is bad conductor of heat so the outside low temperature does not get transferred to body as well as prevent our body heat to escape outside. Hence more layers of cloths keep us warmer during cold winter.

Since, a jute sack is a thermal insulator, therefore, it helps ice not to meit immediately. So, shopkeepers must use insulating materials like sack, saw dust, newspaper etc, to cover the ice.

Yes, she can apply the same method to keep a glass of cold drink cool because wool is a thermal insulator, and it cannot allow heat to pass through it.

Jerks are given to clinical thermometer before using it to settle down the mercury level below normal temperature so that the measurement of temperature of a body can be taken accurately.

As the temperature increases, expansion of mercury takes place in the capillary tube which leads to the rise in the level of mercury in thermometer.

As we know that plastic is a bad conductor of heat due to which the heat from the cooker does not flow to its handle and we can hold it easily. So, this is a reason because of which the handle of a pressure cooker is covered with the thick plastic.

We will prefer white fabric tent in case of summer because it reflects all the radiations from the sun and keeps us cool inside the tent. But in ease of winter, we should not use white fabric tent, we should use black fabric tent as it absorbs all colours of light from the sun and keeps us warm inside the tent.

It cannot reach us by conduction or convection as there is no medium such as air in most part of the space between the earth and the sun. From the sun the heat comes to us by a different process known as radiation which does not require any medium for heat transfer.

In between the layers of cloths there is trapped air. As air is bad conductor of heat so the outside low temperature does not get transferred to body as well as prevent our body heat to escape outside. Hence more layers of cloths keep us warmer during cold winter.

Heat is the total energy of the molecular motion of the substance and temperature is the measure of average energy of the molecular motion in the substance. When we heat a substance it increases the motion of vibrating molecules of the substance thereby increasing the temperature of the substances.

In places of hot climate it is advised that the outer walls of houses be painted white because a light colour absorbs very less radiant heat and we feel comfortable inside such houses due to lower temperature inside house.

Dark surfaces absorb more heat and, therefore, we feel comfortable with dark coloured clothes in the winter whereas light coloured clothes reflect most of the heat that falls on them and, therefore, we feel more comfortable wearing them in the summer.

We will prefer a white fabric tent in case of summer because it reflects all the radiations from the sun and keeps us cool inside the tent. No, in case of winter, we should use a black fabric tent as it absorbs all colours of light from the sun and keeps us warm inside the tent.

As it is a fact that the hot air during the day time surrounds the land gradually and rises up, due to which a convection air of heat develops. So, kites and eagles start moving along this rising current of heat without flapping the wings to fly high up in the sky.

1. As we know that plastic is a bad conductor of heat which does not allow the heat to pass through itself. So, heat from the fry pan does not flow to the handle due to which we can hold it easily. So that’s why, the fry pans are provided with the plastic handles.
2. The value showed by Pooja here is a great concern and careness towards her five years old small daughter.

Two examples of conductors of heat are:

1. Aluminum.
2. Iron.

Two examples of insulators of heat are:

1. Wood.
2. Plastic.

The freezer is located at the top of the refrigerator. It is because the air inside and around the compartments of freezer gets cool and move downwards and on the other side, the lesser cool air moves upward to get cooled. So, as a result of this, convection of heat are setup in the air and the tower section of the . refrigerator also gets cooled faster.

The materials which allow heat to pass through them easily are conductors of heat. For examples, aluminium, iron and copper The materials which do not allow heat to pass through them easily are poor conductors of heat known as insulators such as plastic and wood.

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.

1. The following precautionary measures while checking the fever through a clinical thermometer are

• While reading the clinical thermometer, it should never be held by the bulb.
• The clinical thermometer should be washed properly (before and after use).

2. The values showed by the elder brother of Pankaj, Vishwas, are concern towards the way of using the clinical thermometer and the importance of money as well.

S. No.	Land breeze	Sea breeze
(i)	This is produced from the land to the sea.	It is produced from the sea to the land.
(ii)	It occurs at night.	It occurs during the day.