Matter

Question 1

What is matter in the context of physics?

Answer 1

Matter is anything that has mass and occupies space (volume).

Question 2

What is the difference between mass and weight?

Answer 2

Mass is the amount of matter in an object (in kilograms). Weight is the force due to gravity acting on that mass (in newtons).

Question 3

Name the three primary states of matter and give a brief description of each.

Answer 3

1. Solid: Particles packed closely in a rigid structure.
2. Liquid: Particles relatively free to move; takes shape of its container.
3. Gas: Particles move freely, filling the available volume.

Question 4

Give two examples of changes of state and name the processes.

Answer 4

Melting: Solid to liquid.
Evaporation/Boiling: Liquid to gas.
Condensation: Gas to liquid.
Freezing: Liquid to solid.
Sublimation: Solid to gas.

Question 5

How is density defined, and what is its formula?

Answer 5

Density is mass per unit volume.

Formula: ρ = m/V.

Question 6

What is specific gravity?

Answer 6

Specific gravity is the ratio of a substance’s density to the density of a reference substance (usually water).

Question 7

What is the difference between an atom and a molecule?

Answer 7

Atom: The smallest particle of an element that retains its chemical properties.
Molecule: A group of two or more atoms bonded together, representing the smallest unit of a compound.

Question 8

Define element and compound.

Answer 8

Element: A substance made of only one type of atom (e.g., O₂, Fe).
Compound: A substance formed by the chemical combination of two or more elements (e.g., H₂O).

Question 9

How do mixtures differ from pure substances?

Answer 9

Mixtures: Two or more substances blended but not chemically combined; can often be separated by physical means.
Pure Substances: Have a uniform composition (elements or compounds).

Question 10

What do atomic number and mass number represent?

Answer 10

Atomic number (Z): Number of protons in the nucleus.
Mass number (A): Total number of protons + neutrons in the nucleus.

Question 11

What are isotopes?

Answer 11

Isotopes are variants of an element with the same number of protons but different numbers of neutrons (thus different mass numbers).

Question 12

Explain the difference between ionic and covalent bonds.

Answer 12

Ionic Bonds: Formed by the transfer of electrons between atoms (e.g., NaCl).
Covalent Bonds: Formed by sharing electrons between atoms (e.g., H₂O).

Question 13

State the Law of Conservation of Mass.

Answer 13

Law of Conservation of Mass: In a closed system, mass is neither created nor destroyed during chemical or physical changes.

Question 14

What does the kinetic molecular theory say about particles in matter?

Answer 14

It states that particles (atoms/molecules) are always in motion; the higher the temperature, the faster they move. This motion underlies changes of state and gas behavior.

Question 15

Why do most substances expand when heated?

Answer 15

When heated, particles gain kinetic energy and vibrate/move more, increasing the average distance between them, leading to expansion.

Question 16

What is plasma, often referred to as the “fourth state of matter”?

Answer 16

Plasma is an ionized gas containing free electrons and ions, found in stars and lightning. It is electrically conductive and distinct from solid, liquid, and gas.

Question 17

Give an example of a physical change and a chemical change.

Answer 17

Physical Change: Changes in state or form without altering composition (e.g., ice melting).
Chemical Change: Substance transforms into one or more new substances (e.g., iron rusting).

Question 18

Differentiate between elasticity and plasticity.

Answer 18

Elasticity: Ability of a material to return to its original shape after the deforming force is removed.
Plasticity: Tendency to retain a deformed shape once the force is removed.

Question 19

State Hooke’s Law.

Answer 19

Hooke’s Law: The extension (or compression) of a spring is proportional to the applied force.

Question 20

Define stress and strain in materials.

Answer 20

Stress: Force per unit area.
Strain: Deformation per unit length.

Question 21

Give the definitions of hardness and ductility.

Answer 21

Hardness: A material’s resistance to deformation or scratching.
Ductility: A material’s ability to be drawn into a wire without breaking.

Question 22

What do malleability and brittleness refer to?

Answer 22

Malleability: A material’s ability to be flattened into thin sheets.
Brittleness: Tendency to break or shatter without significant deformation.

Question 23

How is pressure in a fluid (liquid or gas) defined?

Answer 23

Pressure = Force per unit area. In fluids, pressure acts equally in all directions (Pascal’s Principle).

Question 24

State Archimedes’ Principle.

Answer 24

A body immersed in a fluid experiences an upward buoyant force equal to the weight of the fluid it displaces.

Question 25

Differentiate between cohesion and adhesion in liquids.

Answer 25

Cohesion: Attraction between like molecules (e.g., water-water).
Adhesion: Attraction between unlike molecules (e.g., water-glass).

Question 26

What is surface tension?

Answer 26

A property of liquids where the surface acts like an elastic membrane due to cohesive forces among molecules at the surface.

Question 27

How does vapor pressure relate to boiling?

Answer 27

Boiling occurs when the vapor pressure of a liquid equals the external (atmospheric) pressure, allowing bubbles to form.

Question 28

What is sublimation, and give one example.

Answer 28

Sublimation is the phase change from solid directly to gas (or vice versa) without passing through the liquid state.

Example: Dry ice turning into gas.

Question 29

What does thermal conductivity describe?

Answer 29

Thermal conductivity describes how well a material conducts heat; high conductivity (e.g., metals) transfers heat quickly.

Question 30

What is the difference between crystalline and amorphous solids?

Answer 30

Crystalline Solids: Atoms or molecules arranged in an orderly, repeating pattern.
Amorphous Solids: Atoms or molecules lack a long-range order (e.g., glass).