Which of the following changes the state of matter? (a) Heating water (b) Freezing water ** (c) Stirring water (d) Adding salt to water
The correct answer and explanation is:
The correct answer is (b) Freezing water.
Explanation:
A change in the state of matter occurs when a substance transitions from one physical form to another, such as from solid to liquid, liquid to gas, or vice versa. These changes are typically caused by variations in temperature or pressure.
Freezing water involves lowering the temperature of liquid water until it becomes solid ice. This is a classic example of a phase change, where the water molecules slow down, arrange into a rigid structure, and the liquid turns into a solid. This change in state is called freezing or solidification.
On the other hand, heating water (option a) does not necessarily change its state unless the heating continues until water reaches its boiling point and turns into vapor (gas). Simply heating water at lower temperatures only raises its temperature but keeps it in the liquid phase. So, heating water by itself does not guarantee a state change unless it reaches the boiling point.
Stirring water (option c) is a physical action that mixes the water but does not change its state. Stirring only affects the distribution of heat or solutes within the liquid but keeps water in the liquid state.
Adding salt to water (option d) changes the composition of the water by dissolving salt, creating a saltwater solution, but it does not change the water’s state of matter. The water remains liquid, although the freezing and boiling points may be affected due to the dissolved salt.
In summary, freezing water is the process that directly changes the state of matter by converting liquid water into solid ice. This is a fundamental example of a physical change involving a phase transition.