Understanding States of Matter Melting and Freezing

1. What is the process called when a solid turns into a liquid upon being heated?

Freezing

Melting

Sublimation

Burning

Melting is the process where a solid transforms into a liquid when it is heated. As the temperature rises, the particles in the solid gain energy, causing them to vibrate more vigorously. Eventually, this energy overcomes the forces holding the particles in their fixed positions, allowing them to move freely and transition into the liquid state. This process is essential in various natural and industrial contexts, such as ice melting into water or metals melting for casting.

Explanation

Melting is the process where a solid transforms into a liquid when it is heated. As the temperature rises, the particles in the solid gain energy, causing them to vibrate more vigorously. Eventually, this energy overcomes the forces holding the particles in their fixed positions, allowing them to move freely and transition into the liquid state. This process is essential in various natural and industrial contexts, such as ice melting into water or metals melting for casting.

2. When a liquid is cooled and turns into a solid, this process is called ____.

Freezing is the process in which a liquid loses heat and transitions into a solid state. This occurs when the temperature of the liquid drops below its freezing point, causing the molecules to slow down and arrange themselves into a fixed structure, resulting in a solid. Common examples include water turning into ice when the temperature falls below 0 degrees Celsius. This phase change is a fundamental concept in thermodynamics and is essential in various natural and industrial processes.

Explanation

Freezing is the process in which a liquid loses heat and transitions into a solid state. This occurs when the temperature of the liquid drops below its freezing point, causing the molecules to slow down and arrange themselves into a fixed structure, resulting in a solid. Common examples include water turning into ice when the temperature falls below 0 degrees Celsius. This phase change is a fundamental concept in thermodynamics and is essential in various natural and industrial processes.

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3. Burning a substance to produce ash is an example of a permanent change.

True

False

Burning a substance results in a chemical reaction that transforms the original material into new substances, such as ash, gases, and heat. This process alters the molecular structure of the substance, making it impossible to revert to its original form. Since the changes are irreversible and lead to the creation of different materials, burning is classified as a permanent change.

Explanation

Burning a substance results in a chemical reaction that transforms the original material into new substances, such as ash, gases, and heat. This process alters the molecular structure of the substance, making it impossible to revert to its original form. Since the changes are irreversible and lead to the creation of different materials, burning is classified as a permanent change.

4. Which of the following is an example of a temporary change?

Burning wood to ash

Melting ice back to water

Cooking food

Rusting iron

Melting ice back to water is a temporary change because it can be reversed. When ice melts, it transforms into liquid water, but if the temperature drops again, the water can freeze back into ice. This reversible process distinguishes it from permanent changes, such as burning wood to ash or rusting iron, where the original materials cannot be restored.

Explanation

Melting ice back to water is a temporary change because it can be reversed. When ice melts, it transforms into liquid water, but if the temperature drops again, the water can freeze back into ice. This reversible process distinguishes it from permanent changes, such as burning wood to ash or rusting iron, where the original materials cannot be restored.

5. Match each term with its correct description.

Melting Point

Freezing Point

Sublimation

Dry Ice

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6. Which of the following statements about sublimation are correct?

It involves a solid changing directly into a gas

Dry ice is an example of sublimation

It requires the substance to first melt into a liquid

Carbon dioxide can undergo sublimation

Sublimation is the process where a solid transforms directly into a gas without passing through the liquid phase. Dry ice, which is solid carbon dioxide, exemplifies sublimation as it changes to gas at room temperature. Additionally, carbon dioxide can undergo sublimation under specific conditions, reinforcing its role in various applications such as refrigeration. The statement about requiring the substance to first melt into a liquid is incorrect, as sublimation bypasses the liquid state entirely.

Explanation

Sublimation is the process where a solid transforms directly into a gas without passing through the liquid phase. Dry ice, which is solid carbon dioxide, exemplifies sublimation as it changes to gas at room temperature. Additionally, carbon dioxide can undergo sublimation under specific conditions, reinforcing its role in various applications such as refrigeration. The statement about requiring the substance to first melt into a liquid is incorrect, as sublimation bypasses the liquid state entirely.

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7. A substance that has undergone melting can ____ to its original solid form when cooled.

When a substance melts, it transitions from a solid to a liquid state due to the absorption of heat. Upon cooling, the liquid loses energy, allowing the molecules to slow down and re-establish the solid structure. This process is called solidification or freezing. Therefore, the substance can return to its original solid form when the temperature decreases sufficiently, allowing it to regain its solid characteristics.

Explanation

When a substance melts, it transitions from a solid to a liquid state due to the absorption of heat. Upon cooling, the liquid loses energy, allowing the molecules to slow down and re-establish the solid structure. This process is called solidification or freezing. Therefore, the substance can return to its original solid form when the temperature decreases sufficiently, allowing it to regain its solid characteristics.

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8. Which of the following correctly describes the freezing process?

A liquid gains heat and turns into a gas

A liquid loses heat and turns into a solid

A solid gains heat and turns into a liquid

A gas loses heat and turns into a liquid

Freezing is the process where a liquid transitions into a solid state. This occurs when the temperature of the liquid decreases, causing its molecules to lose energy and move closer together. As heat is removed, the arrangement of the molecules becomes more structured, forming a solid. This is the opposite of melting, where a solid gains heat and transforms into a liquid. Thus, the correct description of freezing involves a liquid losing heat to become solid.

Explanation

Freezing is the process where a liquid transitions into a solid state. This occurs when the temperature of the liquid decreases, causing its molecules to lose energy and move closer together. As heat is removed, the arrangement of the molecules becomes more structured, forming a solid. This is the opposite of melting, where a solid gains heat and transforms into a liquid. Thus, the correct description of freezing involves a liquid losing heat to become solid.