Intro to Ecology Practice Questions

What is the smallest unit of matter?

• Molecule

• Atom

• Particle

• Compound

Answer explanation

The smallest unit of matter is the atom, which consists of protons, neutrons, and electrons. Molecules and compounds are made up of atoms, while particles can refer to various subatomic or atomic entities.

What state of matter has molecules that are tightly packed and only vibrate?

• Gas

• Liquid

• Solid

• Plasma

Answer explanation

The correct answer is 'Solid' because in solids, molecules are tightly packed together and can only vibrate in place, unlike gases and liquids where molecules move more freely.

What happens to molecules when a liquid is cooled?

• They stop moving entirely.

• They slow down and move closer together.

• They move faster and spread apart.

• They change into a gas.

Answer explanation

When a liquid is cooled, its molecules lose energy, causing them to slow down and move closer together. This results in increased intermolecular forces, leading to a more compact arrangement.

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NGSS.MS-PS1-4

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In a gas, how do the molecules behave?

• They vibrate but do not move past one another.

• They are close together and slide past each other.

• They move freely and are far apart.

• They do not move.

Answer explanation

In a gas, molecules move freely and are far apart, allowing them to fill the container they are in. This behavior contrasts with solids and liquids, where molecules are closer together and have restricted movement.

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NGSS.MS-PS1-4

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What property of water causes it to bead on wax paper?

• Molecular motion

• Surface tension

• Adhesion

• Density

Answer explanation

Water beads on wax paper due to surface tension, which is the cohesive force between water molecules. This force causes the water to minimize its surface area, resulting in the formation of droplets instead of spreading out.

What does heating a liquid do to its molecules?

• Speeds them up and spreads them apart.

• Slows them down and brings them closer.

• Stops their motion completely.

• Increases their attractions.

Answer explanation

Heating a liquid increases the energy of its molecules, causing them to move faster and spread apart. This is why the correct answer is 'Speeds them up and spreads them apart.'

Tags

NGSS.MS-PS1-4

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What determines whether a substance is a solid, liquid, or gas at a specific temperature?

• Its molecular structure

• The balance between motion and attraction of molecules

• The pressure of the environment

• Its size

Answer explanation

The state of a substance (solid, liquid, gas) is determined by the balance between the motion of its molecules and the attractive forces between them. In solids, attraction dominates; in gases, motion prevails.

Tags

NGSS.MS-PS1-4

What happens to water molecules as they freeze?

• They stop moving completely.

• They move slower and form a fixed arrangement.

• They move faster and spread apart.

• They condense into a gas.

Answer explanation

As water freezes, its molecules move slower due to decreased energy and form a fixed arrangement, creating a solid structure (ice). This is why the correct answer is that they move slower and form a fixed arrangement.

Tags

NGSS.MS-PS1-4

What does the Kinetic-Molecular Theory explain?

• The behavior of molecules in living organisms

• The motion and interaction of particles in matter

• The process of photosynthesis

• The evaporation of liquids

Answer explanation

The Kinetic-Molecular Theory explains the motion and interaction of particles in matter, detailing how particles behave in different states, such as solids, liquids, and gases.

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Why does the liquid in a thermometer rise when heated?

• The glass expands.

• Molecules move faster and push upward.

• The liquid attracts molecules of heat.

• The glass contracts.

Answer explanation

When heated, the molecules in the liquid move faster, causing them to push against each other and rise in the thermometer. This is why the correct answer is that molecules move faster and push upward.

Tags

NGSS.MS-PS1-4