Problem 121 Determine whether each change is... [FREE SOLUTION]

Chapter 4: Problem 121

Determine whether each change is physical or chemical. (Chapter 3\()\) \begin{equation} \begin{array}{l}{\text { a. Water boils. }} \\ {\text { b. A match burns. }} \\\ {\text { c. Sugar dissolves in water. }} \\ {\text { d. Sodium reacts with water. }} \\ {\text { e. Ice cream melts. }}\end{array} \end{equation}

Short Answer

Expert verified

a. Physical change b. Chemical change c. Physical change d. Chemical change e. Physical change

Step by step solution

Understand Physical Change

A physical change alters the form or appearance of a substance, but does not make the substance into another substance. Examples include changes in state, shape, or size.

Determine if Boiling is Physical or Chemical

Boiling is a process where a liquid turns into a gas. Since it's a change of state without altering the chemical identity of water, boiling is a physical change.

Understand Chemical Change

A chemical change transforms the substance into a new one with a different chemical composition. It is usually irreversible under normal conditions and involves the making or breaking of bonds.

Analyze Burning of a Match

When a match burns, a chemical reaction takes place that transforms the matchstick and oxygen into ash and different gases. This is a chemical change because new substances are formed.

Determine if Dissolving Sugar is Physical or Chemical

Dissolving sugar in water involves sugar dispersing into water molecules, which can be reverted by evaporating the water. Therefore, dissolving is a physical change.

Evaluate Sodium Reacting with Water

When sodium reacts with water, it produces sodium hydroxide and hydrogen gas, indicating a change in chemical composition and the formation of new substances. It's a chemical change.

Analyze Ice Cream Melting

Melting is the process where a solid turns into a liquid. Since ice cream melting does not change its chemical structure, it is a physical change.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

States of Matter

Matter exists in different states, primarily solid, liquid, and gas. These states are determined by the arrangement and energy of the particles within a substance.

Solid: Particles are closely packed together in a fixed position. This state has a definite shape and volume.

Liquid: Particles are close, but can move past one another. Liquids have a definite volume but can take the shape of their container.

Gas: Particles are far apart and move freely, filling the volume and shape of their container.

Transitions between these states, like boiling (liquid to gas) and melting (solid to liquid), are examples of physical changes since they involve changes in state without altering the substance's chemical identity.

Chemical Reactions

Chemical reactions occur when substances interact to form new substances with different chemical properties. These reactions involve breaking bonds in reactants and forming new ones in products. Certain conditions are often needed for these reactions to happen, such as temperature, pressure, or the presence of catalysts.

Irreversibility: Chemical reactions often cannot be reversed by simple physical means.

Energy Changes: Reactions can either absorb (endothermic) or release (exothermic) energy, often in the form of heat.

For instance, when a match burns, it reacts with oxygen to form new substances like ash and gases, indicating a chemical change. Similarly, when sodium reacts with water, it forms sodium hydroxide and hydrogen gas, showcasing another chemical reaction.

Physical Properties

Physical properties are characteristics of a substance that can be observed or measured without changing its chemical identity. Examples include:

State: Whether a substance is a solid, liquid, or gas.

Melting and Boiling Points: Temperatures at which substances transition between different states.

Density: The mass per unit volume of a substance.

These properties can help us identify substances and understand how they might behave in different situations. For example, water boiling, which is a physical change, demonstrates how the temperature of 100掳C is a physical property indicating the transition from liquid to gas.

Chemical Properties

Chemical properties describe a substance's potential to undergo chemical change or reaction based on its composition. These include:

Reactivity: How a substance interacts with other substances, such as water or acids.

Flammability: The ability of a substance to burn in the presence of oxygen.
Corrosion: The gradual destruction of materials, often metals, due to chemical reactions with the environment.

Understanding chemical properties is essential for predicting how substances will behave in various chemical reactions. For instance, sodium鈥檚 high reactivity with water can lead to vigorous and spontaneous reactions, forming new chemical substances.

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Short Answer

Step by step solution

Understand Physical Change

Determine if Boiling is Physical or Chemical

Understand Chemical Change

Analyze Burning of a Match

Determine if Dissolving Sugar is Physical or Chemical

Evaluate Sodium Reacting with Water

Analyze Ice Cream Melting

Key Concepts

States of Matter

Chemical Reactions

Physical Properties

Chemical Properties

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