3: Change of State Flashcards
What does a substance undergo when it’s temperature is at the melting point? Does it absorb or give out energy?
Fusion (melting), which is meant by the change of state of matter. The substance absorbs energy in fusion.
Why does a bottle of melting ice feel colder than a bottle of water (both at 0degrees Celsius) after being held for a while?
Both the melting ice and the cold water absorb energy from the surroundings. However, the energy absorbed by the ice are used for it to change its state, so it’s temperature does not increase. Meanwhile, the energy absorbed by the water is used to change the temperature of the water.
What is latent heat?
Latent heat means hidden heat, which is the heat absorbed by a substance during its change of state.
What is the name of the process of a substance changing from liquid state to gas state?
Boiling, which is a type of vaporisation.
What is the shape of a heating curve?
The curve consists of first a concave down increasing part, and a concave up increasing part. (The substance heats up, stops temperature change when changing its state, and keeps heating up.)
What is the shape of a cooling curve?
The cooling curve is joined by a concave up decreasing graph and a concave down decreasing graph. (The substance cools down, stops temperature change when it changes its state, then keeps cooling down.)
What is called when a substance changes its state from liquid state to solid state? What is the property of the period of change of state?
Solidification. The substance releases latent heat but it’s temperature does not change because it is changing its state.
What is the name of the process of a substance changing from gas state to liquid state? Is energy absorbed or released?
Condensation, the energy (latent heat) is released by the substance
What are the names for the types of energy corresponding to the conversion between solid and liquid states, and liquid and gaseous states respectively?
Solid and liquid states: latent heat of fusion
Liquid and gaseous states: latent heat of vaporisation
What is specific latent heat?
Specific latent heat of a substance is the amount of energy transferred by heating to change the state of 1kg of the substance without a change in temperature.
What is the formula and unit for specific latent heat?
Latent heat is equal to the heat given out divided by the mass of the substance (l=Q/m). It is measured in J*kg^-1.
What is the specific latent heat of fusion of ice?
3.34*10^5 J kg^-1
What is the the definition and the specific latent heat of vaporisation of water?
The specific latent heat of vaporisation of water is the energy needed to change 1kg of water into steam without changing its temperature. It is equal to 2.26*10^6 J kg^-1.
