Ans : As evaporation occur on the surface of liquid.
Q. List two processes from which it may be concluded that the particles of a gas move continuously.
Ans: Compressibility and Brownian movement
Q. At what temperature does solid ice and liquid water co-exist together?
Ans: At 00C, the three phases of water co exist called triple point.
Q. What is common among the three states of matter?
Ans: They all contain molecules.
Q. . Which property of gas is used in supplying oxygen cylinders to hospitals?
Q. a substance x was highly compressible and could easily be liquefied. it could also take the shape of the container. Predict the nature of the substance
Q. What is the state of water at 100 degree celsius, zero degree celsius and 4 degree celsius?
Ans: The state of water in 100 degree celcius is gas, in 0 degree celcius it is solid and in 4 degree celcius it is liquid
Q. can a liquid turn into vapor without heating?
Ans: yes, By the process of evaporation as vaporization of water occur below the boiling point under atmospheric pressure.
Q. What do you mean by Latent heat of Fusion?
Ans: the heat required to change 1 kg of a solid substance into liquid state at the melting point of the substance. For example, amount of heat required to melt ice at 0 ° C into water, at 0 ° C will be known as the Latent Heat of Fusion of ice.
Q. What is compressibility? How it is negligible in solids?
Ans: Compressibility is the ability of a substance to be reduced to its volume under pressure. Solids are incompressible as their particles are held together. So, we can tell that compressibility is negligible in solids.
Q. Two cubes of ice are pressed hard between two palms. After releasing the pressure, the cubes join together. Why?
Ans: Pressure is directly proportional to temperature when we apply pressure, temp. Increases then the ice in contact melts and it turns into water. when pressure is removed, the temperature decreases again and melted ice again freezes .Hence cubes join together.
Q. Explain why ice has lower density than water?
Ans: The mass per unit volume of a substance is called density (density = mass/volume). As the volume of a substance increases, its density decreases.
When water changes into ice, space between particles increases. These spaces are larger as compared to the spaces present between the particles of water. Thus, the volume of ice is become greater than that of water. Hence, the density of ice became lower than that of water. As, a substance with lower density than water can float on water. Therefore, ice floats on water.