Which of the following are chemical changes?
a. mercury has a density of 13600 kg/m3
b. potassium reacts with water
c. hammer a nail into a piece of wood
d. a rotting apple
e. potassium is a soft metal
f. evaporation of water g. sublimation of dry ice
h. dissolve sugar in water
i. a growing flower
j. hydrogen is a flammable gas
b. potassium reacts with water
d. a rotting apple
g. sublimation of dry ice
h. dissolve sugar in water
j. hydrogen is a flammable gas
The chemical changes among the given options are:
b. Potassium reacts with water.
d. A rotting apple.
f. Evaporation of water.
g. Sublimation of dry ice.
h. Dissolve sugar in water.
j. Hydrogen is a flammable gas.
These changes involve a chemical transformation or a chemical reaction, resulting in the formation of new substances with different properties.
To determine which of the following are chemical changes, we need to understand what a chemical change is. A chemical change refers to a process that results in the formation of a new substance with different chemical properties.
a. Mercury has a density of 13600 kg/m3: This is a physical property of mercury and does not involve any change in its chemical composition. Therefore, it is not a chemical change.
b. Potassium reacts with water: This is a chemical change because it involves a reaction between potassium and water, resulting in the formation of a new substance with different properties.
c. Hammer a nail into a piece of wood: This is a physical change because it involves a change in the shape or position of the nail and wood. The chemical composition of the nail and wood remains unchanged.
d. A rotting apple: This is a chemical change. The rotting process involves the breakdown of organic compounds in the apple due to biochemical reactions, resulting in the formation of new substances with different properties.
e. Potassium is a soft metal: This is a physical property of potassium and does not involve any change in its chemical composition. Therefore, it is not a chemical change.
f. Evaporation of water: This is a physical change because it involves the change of state from liquid to gas without any change in the chemical composition of water.
g. Sublimation of dry ice: This is a physical change because it involves the change of state from solid to gas without any change in the chemical composition of carbon dioxide (dry ice).
h. Dissolve sugar in water: This is a physical change because it involves the sugar molecules dispersing in water without any change in their chemical composition.
i. A growing flower: This is a biological process involving cellular activities and growth. While it may involve some chemical reactions within the cells, the process as a whole is not considered a chemical change.
j. Hydrogen is a flammable gas: This is a physical property of hydrogen and does not involve any change in its chemical composition. Therefore, it is not a chemical change.
In summary, the chemical changes among the options are:
b. Potassium reacts with water
d. A rotting apple