States of Matter and Energy Changes

Which state of matter has a definite shape and volume?

• Solid

• Liquid

• Gas

• Plasma

Answer explanation

A solid has a definite shape and volume, meaning it maintains its form and does not change unless acted upon by an external force. In contrast, liquids take the shape of their container, and gases and plasma do not have a definite shape or volume.

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DOK Level 1: Recall

NGSS.MS-PS1-4

What is the smallest unit of a chemical element that retains its chemical properties?

• Molecule

• Atom

• Compound

• Mixture

Answer explanation

The smallest unit of a chemical element that retains its chemical properties is an atom. Molecules are made of atoms, compounds consist of different atoms, and mixtures are combinations of substances, but only atoms are the fundamental units.

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DOK Level 1: Recall

NGSS.MS-PS1-1

Which of the following is a physical change?

• Burning wood

• Rusting iron

• Melting ice

• Baking a cake

Answer explanation

Melting ice is a physical change because it involves a change in state from solid to liquid without altering the chemical composition. In contrast, burning wood, rusting iron, and baking a cake involve chemical changes.

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DOK Level 1: Recall

NGSS.MS-PS1-4

What happens to the particles in a gas when it is cooled?

• They move faster

• They move slower

• They stay the same

• They disappear

Answer explanation

When a gas is cooled, the thermal energy of its particles decreases, causing them to move slower. This reduced movement leads to a decrease in temperature and pressure, confirming that the correct answer is "They move slower."

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DOK Level 1: Recall

NGSS.MS-PS1-4

Which of the following is a chemical property?

• Color

• Density

• Flammability

• Melting point

Answer explanation

Flammability is a chemical property because it describes a substance's ability to undergo a chemical change when exposed to fire. In contrast, color, density, and melting point are physical properties.

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DOK Level 1: Recall

NGSS.MS-PS1-4

Which of the following best describes the atomic composition of water?

• Two hydrogen atoms and one oxygen atom

• One hydrogen atom and two oxygen atoms

• Two oxygen atoms and one hydrogen atom

• One oxygen atom and one hydrogen atom

Answer explanation

Water is composed of two hydrogen atoms and one oxygen atom, forming the chemical formula H2O. This is the correct representation of water's atomic structure, making the first answer choice accurate.

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DOK Level 2: Skill/Concept

NGSS.MS-PS1-1

What is the process called when a liquid changes into a gas?

• Condensation

• Evaporation

• Freezing

• Sublimation

Answer explanation

The process when a liquid changes into a gas is called evaporation. This occurs when molecules in the liquid gain enough energy to overcome intermolecular forces and enter the gas phase.

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DOK Level 1: Recall

NGSS.MS-PS1-4

Which of the following models best represents a solid?

• Particles are tightly packed and vibrate in place

• Particles are loosely packed and slide past each other

• Particles are far apart and move freely

• Particles are ionized and move freely

Answer explanation

The correct choice describes a solid where particles are tightly packed and vibrate in place, reflecting the fixed shape and volume of solids. Other options describe liquids or gases, which do not fit the characteristics of a solid.

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DOK Level 2: Skill/Concept

NGSS.MS-PS1-4

Which of the following is true about the atomic structure of gases?

• They have a fixed volume and shape

• They have a fixed volume but no fixed shape

• They have no fixed volume or shape

• They have a fixed shape but no fixed volume

Answer explanation

Gases have no fixed volume or shape because their particles are widely spaced and move freely. This allows them to expand and fill any container, unlike solids and liquids which have defined shapes and volumes.

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DOK Level 2: Skill/Concept

NGSS.MS-PS1-4

Which of the following best describes a chemical change?

• A change in state

• A change in color

• A change in temperature

• A change that produces a new substance

Answer explanation

A chemical change involves a transformation that results in the formation of a new substance, unlike physical changes such as changes in state, color, or temperature, which do not alter the substance's chemical identity.

Tags

DOK Level 2: Skill/Concept

NGSS.MS-PS1-4