Physical and Chemical Changes

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What is a physical change?

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A physical change is a change in the form or state of matter without any change in its chemical composition.

Answer explanation

A physical change involves a transformation in the form or state of matter, such as changes in phase (solid, liquid, gas) or shape, while its chemical composition remains unaltered. The correct option emphasizes this distinction between physical changes and chemical changes, which involve alterations in molecular structure and composition.

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Give an example of a physical change.

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Melting ice into water

Answer explanation

A physical change is a change in the state or form of a substance without changing its chemical composition. Melting ice into water is an example of a physical change, as the ice (solid) changes into water (liquid) without altering its chemical structure, which is still H2O.

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What is a chemical change?

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A chemical change is a process that results in the formation of new substances with different chemical properties.

Answer explanation

A chemical change occurs when a process leads to the formation of new substances that have different chemical properties from the original substances. This transformation involves the breaking and forming of chemical bonds, resulting in new substances with distinct chemical properties as compared to the initial substances.

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Example of a chemical change.

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Burning of wood

Answer explanation

A chemical change involves the formation of new substances with different properties due to the rearrangement of atoms. In the case of burning wood, the wood undergoes a chemical reaction with oxygen, producing new products like ash, carbon dioxide, and water vapor. This is an example of a chemical change, as opposed to physical changes like cutting paper, mixing salt and water, or melting ice, which do not result in new substances being formed.

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What are the three states of matter?

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solid, liquid, and gas

Answer explanation

The three states of matter mentioned in the question are solid, liquid, and gas. These states are distinguished by the arrangement and movement of particles in the substances. In a solid, particles are closely packed and vibrate in place. In a liquid, particles are close but can move around, allowing the substance to flow. In a gas, particles are spread out and move freely. Plasma is another state of matter, but it is not included in the provided answer.

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What is a solid?

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A solid is a state of matter characterized by particles that are closely packed together and have a definite shape and volume.

Answer explanation

A solid is a state of matter in which particles are closely packed together, giving it a definite shape and volume. The correct option highlights these characteristics, differentiating it from other states of matter with varying particle arrangements and properties.

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What is a liquid?

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A liquid is a state of matter that has a definite volume but no definite shape.

Answer explanation

A liquid is a state of matter characterized by having a definite volume but no definite shape. It flows and takes the shape of its container, while maintaining its volume. This distinguishes it from other states of matter, such as solids, which have a definite shape and volume, and gases, which have no definite shape or volume.

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What is a gas?

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A gas is a state of matter that has no definite shape or volume.

Answer explanation

A gas is a state of matter that has no definite shape or volume, unlike solids and liquids. In this state, molecules move freely and spread out to fill any available space, making gases highly compressible and able to conform to the shape of their containers. This explains why the correct choice is that a gas has no definite shape or volume.

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Example of a physical change in matter from solid to liquid.

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Melting

Answer explanation

Melting is the correct answer because it is the process where a substance changes from a solid to a liquid due to an increase in temperature or pressure. In contrast, condensation involves a gas changing into a liquid, sublimation is a solid turning directly into a gas, and evaporation is a liquid turning into a gas.

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Example of a chemical change in matter changing from a liquid to a gas.

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Water vapor

Answer explanation

A chemical change can occur when matter changes from one state to another, such as liquid to gas. In this case, water vapor is the correct choice because it represents the gaseous state of water, which is a result of a chemical change. Evaporation is a physical change, while steam and condensation are related to the water cycle but not directly indicative of a chemical change.