Energy & Matter: What do I know about Matter and Heat

What is the smallest part of a chemical element that can exist?

• Atom

• Molecule

• Proton

• Electron

Answer explanation

The smallest part of a chemical element that can exist independently is an atom. Atoms consist of protons, neutrons, and electrons, but they are the fundamental units of elements, unlike molecules, which are combinations of atoms.

Which of the following is NOT a state of matter?

• Solid

• Liquid

• Gas

• Plasma

Answer explanation

Plasma is actually a state of matter, along with solid, liquid, and gas. Therefore, none of the options listed are NOT a state of matter. The question may be misleading.

What term is used to refer to both single atoms and molecules?

• Particle

• Compound

• Element

• Solution

Answer explanation

The term 'particle' encompasses both single atoms and molecules, making it the correct choice. 'Element' refers to a type of atom, 'compound' refers to molecules made of different elements, and 'solution' is a mixture.

What happens to particles in solids, liquids, and gases when they are heated?

• They move closer together

• They move away from each other

• They stop moving

• They disappear

Answer explanation

When heated, particles in solids, liquids, and gases gain energy and move faster, causing them to move away from each other. This is why the correct answer is that they move away from each other.

Which instrument is used to measure temperature?

• Barometer

• Thermometer

• Hygrometer

• Calorimeter

Answer explanation

The correct instrument to measure temperature is a thermometer. A barometer measures atmospheric pressure, a hygrometer measures humidity, and a calorimeter measures heat transfer.

At what point does a solid turn into a liquid?

• Boiling point

• Freezing point

• Melting point

• Sublimation point

Answer explanation

A solid turns into a liquid at its melting point, which is the temperature at which the solid's structure breaks down, allowing it to flow as a liquid. The boiling point refers to the transition from liquid to gas, not solid to liquid.

What is the process called when a substance changes directly from a solid to a gas?

• Condensation

• Sublimation

• Melting

• Freezing

Answer explanation

The process of changing directly from a solid to a gas is called sublimation. This occurs without passing through the liquid phase, unlike melting or freezing, which involve changes between solid and liquid states.

Which of the following best describes a physical change?

• The substance stays the same but changes from one physical state to another

• The substance is destroyed

• New substances with different properties are formed

• The substance disappears

Answer explanation

A physical change involves a change in the state of a substance (like melting or freezing) without altering its chemical composition. Thus, the correct choice is that the substance stays the same but changes from one physical state to another.

Why do solids and liquids tend to be harder to compress than gases?

• Their particles are far apart

• Their particles are much closer together

• They have no particles

• Their particles are moving very fast

Answer explanation

Solids and liquids are harder to compress than gases because their particles are much closer together. This close packing means there is less space to reduce, making compression more difficult compared to gases where particles are far apart.

What happens to the density of most substances when they are cooled?

• Density decreases

• Density increases

• Density stays the same

• Density becomes zero

Answer explanation

When most substances are cooled, their particles move closer together, leading to an increase in density. Therefore, the correct answer is that density increases.