The room temperature on Celsius scale is 25°C. What is the temperature on the Kelvin scale?
K = °C + 273,
25°C = 273 + 25 = 298K.
So, temperature of 25°C is equal to 298K.
The melting points of two solids [A] and [B] are 300K and 350K respectively. Which has more inter-particles forces?
With increase in temperature, inter-particles forces decreases. As the melting point of solid A is less than Solid B. Solid B has more inter-particle forces of attraction. Higher the melting point more the inter-particle force.
Which of the following is not endothermic process?
An endothermic process is any process which requires or absorbs energy from its surroundings, usually in the form of heat. It may be a chemical process, such as dissolving ammonium nitrate in water, or a physical process, such as the melting of ice cubes. Insoluble heavy impurities involve the opposite of an endothermic process which is exothermic process one that absorbs energy in the form of heat.
The two major gases present in air are
Air is a mixture of gases. Two main constituent of air are Oxygen (21%) and Nitrogen (78%). Other gases includes carbon dioxide, helium, water vapour etc.
Statement A: In Kelvin temperature, the symbol (∘) is not used.
Statement B: Mercury is used in glass thermometers because it does not stick with glass.
Which of the two statements is true?
In Kelvin temperature, the symbol (∘) is not used. Mercury is used in glass thermometers because it does not stick with glass and have shiny surface to viewed easily.
Match the following with correct response.
solid carbon dioxide is known as dry ice. The reduced evaporation is called humidity. Evaporation is increased by temperature. The liquefied gas increases pressure and reduces temperature.
Which of the following solids undergo sublimation upon heating?
The process of changing solid directly into gases without changing into liquid is called sublimation. In the substance given above only Iodine is a sublime substance.
Which of the following is not a compound?
Brass is a homogeneous mixture of copper and zinc.
Name one common substance which can undergo a change in state upon heating or cooling.
Water can undergo a change in state upon heating and cooling. On heating above 1000C water change into gaseous state and on cooling below 00C it changes into solid state.
Rate of diffusion is the fastest in
Rate of diffusion in gases is high because they have large intermolecular space and they possess more kinetic energy than liquids and gases.
When the liquid starts boiling, the further heat energy which is supplied
When the liquid starts boiling, the further heat energy which is supplied is absorbed as latent heat of vaporization by the liquid to change its state of matter.
Sulphur dioxide is collected in the lab in a gas jar by upward displacement of air. Which of the following statement is correct regarding the density of the gas?
At room temperature, sulfur dioxide is a nonflammable, colorless gas that is heavier than air. Its strong, pungent odor and irritating properties usually provide adequate warning of its presence.
Pressure on the surface of a gas is increased. What will happen to the inter-particle forces?
When the pressure on the surface of a gas is increased. The particles of gases comes closer that increase the inter-particle force of attraction.
What are the characteristics of the particles of matter?
A. Particles of matter are in continuous motion
B. Particles of matters do not have spaces between them
C. Particles of matter attract each other
D. Particles of matter are very large in size
The characteristics of particles of matter are as follows:
1. Particles of matter have space between them
When we dissolve salt in water, it is observed that the particles of salt get evenly distributed in water. Also, it is observed that the presence of salt particles did not change the level of water in the beaker. This could be possible only if the particles of salt were accommodated in between the water particles. Thus, this clearly proves that space exists between water particles.
2. Particles of matter are in continuous motion
We know that there is a lot of space present between the particles of matter. Particles of matter are never at rest and keep moving continuously in these free spaces. The particles of matter move continuously and their speed increases with an increase in temperature.
3. Particles of matter attract each other
The particles of matter attract each other. However, this force of attraction varies from matter to matter.
Statement A: Evaporation is a surface phenomenon but boiling is not.
Statement B: The diffusion of the gases varies inversely as the square root of their densities.
Which of the two statements is true?
Evaporation is a surface phenomenon as takes place only on the surface of liquid but boiling is a bulk phenomenon. The rate of diffusion of gases varies inversely as the square root of their densities.
Statement A: The temperature of the liquid becomes constant once it starts boiling
Statement B: Pressure of air at sea level is 70cm
Which of the two statements is true?
The temperature of the liquid becomes constant once it starts boiling. The heat is used to change the state of matter. The pressure of air at the sea level is 760mm of Hg. So, statement A is correct only.
In which one of the following sets is each one a solid under ordinary conditions-
In the different sets of substance given above, salt, sugar and chalk are solid under ordinary temperature. As Mercury, water and oxygen and nitrogen are not solid.
A substance upon heating directly changes into gaseous state. What is this change called?
The process of changing solids into gases without changing into liquid state or gases directly into solid is called sublimation.
Which of the following is needed by surgeons during surgery?
Before its development as a surgical anesthetic, ether was used throughout the history of medicine, including as a treatment for ailments such as scurvy or pulmonary inflammation. A pleasant-smelling, colorless and highly flammable liquid, ether can be vaporized into a gas that numbs pain but leaves patients conscious.
Name a process by which an impure sample of naphthalene can be purified.
Impure sample of naphthalene can be purified by sublimation process. During this process, naphthalene being sublime changes into vapours leaving behind impurities. Vapour can be cooled by condensation.
A gas can be best liquefied
State of matter can be changed by changing temperature and pressure. A gas can be liquefied by increasing the pressure and reducing the temperature to brings the particle close to each other.
A liquid is kept in an open china dish. A The evaporation of the liquid can be accelerated
A liquid is kept in an open china dish. The evaporation of the liquid can be accelerated by keeping the dish in the open, by blowing air into the liquid or by keeping the dish under a running fan. Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. The surrounding gas must not be saturated with the evaporating substance.
The evaporation of a liquid occur only at
The process of changing liquid into gases from its upper surface at all temperature is called evaporation. Rate of evaporation increase with increase in temperature, surface area and wind speed.
Which of the following is not a chemical reaction?
Boiling is a physical process. When boiling takes place, particles in the substance vibrate more and of weak intermolecular bonds are broken in order for the substance being heated to move into the gaseous phase. Covalent bonds are not broken when boiling occurs. This means that no chemical reaction has taken place. The ratio in which the atoms are bonded together in a substance remains constant.
Which of the following is the nuclear fuel in the sun?
Hydrogen as a fuel in Sun. The source of Sun's incessant energy is hydrogen which is continuously converting to helium through nuclear fusion reaction releasing energy.