Matter In Our Surroundings - Olympiad Level MCQ, Class 9, Science - Class 9 MCQ

Adding salt to water results in a phenomenon called boiling point elevation.

NaCl readily dissolves in water, but unlike water molecules, trying to move dissolved sodium or chlorine ions into the vapour phase requires very large amounts of energy. The boiling point of (pure) water is 100 degree C and at this temperature, the dissolved ions simply remain in solution.

The effect is quite small. Dissolving 60 g of salt in a litre of water only raises the boiling point from 100.0 deg C to 100.5 deg C.

The mixture of ethane,butane and propane is called as LPG (liquified petroleum gas). It is mainly composed of butane and propane but has a little composition of ethane in it. The mixture of butane, ethane and propane is called as the Liquefied Petroleum Gas.

The model, called the kinetic theory of gases, assumes that the molecules are very small relative to the distance between molecules. The molecules are in constant, random motion and frequently collide with each other and with the walls of any container.​

The Triple Point of water is 0.01 Degree Centigrade.That is 273.16 Kelvin.

The liquid is a substance with indefinite shape. They have weak intermolecular space so they are not closely packed, So they have spaces between the molecules. When sugar is added, the glucose molecules occupy these spaces and do not cause an overflow.

Hence, 1 and 2 are true and 2 correctly explains 1.

Van der Waal's forces include attraction and repulsion between atoms, molecules, and surfaces, as well as other intermolecular forces.

If we increase the temperature of the gas molecules, they would possess greater kinetic energy and this will have hyped Brownian effect due to which it will strike the container surface with more energy or pressure.

Ice is more effective in cooling than water at the same temperature because ice can absorb latent heat as well as the heat energy in order to attain room temperature. Water at 0 C can absorb heat energy only to attain the room temperature.

Mist

- The difference between the mist and fog is that mist contains more moisture than fog.

- In mist each nuclei contains a thicker layer of moisture.

- Mists are frequent over mountains as the rising warm air up the slopes meets a cold surface.

- Mist is also formed by water droplets, but with less merging or coalescing. This means mist is less dense and quicker to dissipate.

- Fogs are drier than mist and they are prevalent where warm currents of air come in contact with cold currents.

- In mist visibility is more than one kilometer but less than two kilometres.

Humidity is the amount of water vapour present in the atmosphere. Thus, as water vapour is gaseous and gases are matter, humidity is due to matter. Humidity is not a matter, as humidity is the phenomenon of being humid.

Use formula,
1.8*C = F - 32°
here, C = temperature in °C
          F = temperature in °F
as C = F = k(assume)
So using above formula
1.8*k = k - 32°
=> k = - 40°

The latent heat of vaporization of water is 540 cal/g/°C and the latent heat of fusion of ice is 80 cal/g/°C. At higher pressures, it takes more than 540 calories for every gram to vaporize. 

The correct answer is: (1) and (2) are true and (2) explains (1)
 

Here's the explanation:

• Aquatic life in polar regions: In the polar regions, the surface water of lakes, rivers, and oceans often freezes, forming a layer of ice. This ice serves as an insulator, preventing the water beneath the ice from freezing and maintaining a stable temperature for aquatic life to survive.
• High latent heat of fusion: Water has a high latent heat of fusion, which means it takes a large amount of energy to change its state from solid (ice) to liquid (water) or vice versa. The ice layer in the polar regions acts as a barrier, keeping the heat of the water below it from escaping into the cold atmosphere. This helps to maintain the temperature of the water, ensuring the survival of aquatic life.
• Connection between (1) and (2): The survival of aquatic life in polar regions is supported by the unique properties of water, such as its high latent heat of fusion. The ice layer prevents heat from escaping, maintaining a stable temperature in the water beneath it. Thus, statement (2) explains the reason behind the safety of aquatic life in polar regions as mentioned in statement (1).

Boiling point is a temperature at which vapour pressure of liquid is equal to the atmospheric pressure around it. When we increase the temperature, the molecules of liquid move away from each other due to expansion. And this is why boiling point of a liquid increases with increase in temperature.

Kelvin is the SI unit of Temperature. Kelvin (K) is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. The temperature 0 K is commonly referred to as "absolute zero."

The particles of steam has highest kinetic energy because steam is in the form of gases in which the particles of gases are much apart from one another. The space between the particles of gases are very large. The force of attraction between the particles of gases is almost negligible. The particles of gases are free to move in any direction. When we heated the particles of gases it can move very rapidly. Hence, it's kinetic energy is maximum.

Solid CO₂ is called dry ice. Because it looks like ice & it is cold like ice. But when it melts it does not becomes as a wet liquid. But when ice melts it forms liquid. This is the reason that solid CO₂ is called dry ice.

TF = 9/5 TC + 32

104 = (9/5 x TC) + 32

Therefore, TC = 40

                  K = TC + 273.15

                  So, TC = 40

                  K = 40 + 273.15 = 313.15 K

Boiling is the process by which a liquid turns into a vapor when it is heated to its boiling point. The change from a liquid phase to a gaseous phase occurs when the vapor pressure of the liquid is equal to the atmospheric pressure exerted on the liquid. Boiling is a physical change and molecules are not chemically altered during the process.

When ice is converted into water heat is absorbed by the ice, so the molecules of ice increase their energy and convert into water.

The breeding, rearing, and transplantation of fish by artificial means is called pisciculture, in other words, fish farming. It is the principal form of aquaculture, while other methods may fall under mariculture. It involves raising fish commercially in tanks or enclosures, usually for food.

Aseel is an important native chicken breed of India, known for its martial qualities (aggressive fighting abilities), pugnacity, and majestic gait. The aim of the study is to conserve and characterize the Aseel germplasm, which is considered to be endangered. 

Foot-and-mouth disease (FMD) is a severe, highly contagious viral disease of cattle and swine. It also affects sheep, goats, deer, and other cloven-hooved ruminants. FMD is not recognised as a zoonotic disease.The disease spreads very quickly if not controlled and because of this is a reportable disease.