Name the property that each change depends on. Then classify the property as either chemical or physical.
a) You separate a mixture of gravel and road salt by adding water to it
b) Carbon dioxide gas freezes at a temperature of -78C
a) The property that the change depends on is solubility. Solubility refers to the ability of a substance to dissolve in another substance. In this case, water is added to the mixture of gravel and road salt. The gravel is insoluble in water, so it will not dissolve. On the other hand, road salt (sodium chloride) is soluble in water, which means it will dissolve when water is added. By adding water, the road salt dissolves and can be separated from the insoluble gravel.
The property of solubility is a physical property. Physical properties are characteristics of a substance that can be observed or measured without changing the chemical composition of the substance. In this case, the solubility of road salt in water is a physical property because it does not involve a change in the chemical composition of the road salt.
b) The property that the change depends on is temperature. Temperature refers to the measure of the average kinetic energy of the particles in a substance. In this case, carbon dioxide gas freezes at a temperature of -78°C, which means that at or below this temperature, carbon dioxide gas will change its state from a gas to a solid (freeze).
The property of temperature is a physical property. It is a measure of the energy level of particles in a substance and does not involve a change in the chemical composition of the substance.
physical and physical
Adding water to salt and gravel just dissolves the salt. However, the salt is still salt and the gravel still gravel so no reaction took place.
Same thing with CO2. Water freezes at zero C and boils at 100 C BUT whether it is in the form of solid ice, liquid water, or water vapor (steam) it still is H2O. So physical.