lecture 1 - states of matter

Question 1

What is matter?

Answer 1

Matter is anything with mass and volume (occupies space).

Question 2

How is matter classified by physical state?

Answer 2

Matter is classified into three physical states: solid, liquid, and gas.

Question 3

What are the characteristics of a solid?

Answer 3

A solid has a fixed volume and shape; atoms are arranged in a regular pattern.

Question 4

What are the characteristics of a liquid?

Answer 4

A liquid has a fixed volume but no fixed shape; particles can slide past one another.

Question 5

What are the characteristics of a gas?

Answer 5

A gas has neither fixed shape nor volume; particles move freely in random directions.

Question 6

How is matter classified by composition?

Answer 6

Matter is classified into elements, compounds, and mixtures.

Question 7

What is an element?

Answer 7

An element is a pure substance consisting of only one type of atom (e.g., Fe, O).

Question 8

What is a compound?

Answer 8

A compound is a substance formed from two or more elements bonded together (e.g., H₂O).

Question 9

What is a mixture?

Answer 9

A mixture is a physical combination of two or more substances without chemical bonding.

Question 10

What is an atom?

Answer 10

An atom is the smallest building block of matter, electrically neutral.

Question 11

What is the atomic number?

Answer 11

The atomic number is the number of protons (equals electrons in a neutral atom).

Question 12

What is the mass number?

Answer 12

The mass number is the sum of protons and neutrons.

Question 13

What are isotopes?

Answer 13

Isotopes are variants of an element with the same number of protons but different neutrons.

Question 14

What is a molecule?

Answer 14

A molecule is a group of two or more atoms bonded covalently.

Question 15

What is the difference between molecules and compounds?

Answer 15

Molecules can be of the same element (e.g., O₂), but compounds must have different elements (e.g., CO₂).

Question 16

What is the particle behavior in solids?

Answer 16

In solids, particles are tightly packed in a fixed arrangement with minimal movement, primarily vibrational.

Question 17

What is the particle behavior in liquids?

Answer 17

In liquids, particles are close but can move past each other, maintaining a fixed volume and taking the shape of the container.

Question 18

What is the particle behavior in gases?

Answer 18

In gases, particles are far apart with high energy, having no fixed volume or shape.

Question 19

What factors affect the state of matter?

Answer 19

Temperature and pressure influence particle motion and arrangement, determining the state of matter.

Question 20

Why do atoms bond?

Answer 20

Atoms bond to achieve a more stable, lower-energy state.

Question 21

What are valence electrons?

Answer 21

Valence electrons are key to bonding.

Question 22

What do chemical bonds do?

Answer 22

Chemical bonds lower the potential energy between interacting atoms.

Question 23

What is an ion?

Answer 23

An ion is a charged particle formed when atoms lose or gain electrons (e.g., Na⁺, Cl⁻).

Question 24

What is a chemical formula?

Answer 24

A chemical formula represents types and numbers of atoms in a compound (e.g., NH₃ for ammonia with 1 nitrogen and 3 hydrogen atoms).

Question 25

What are the three physical states of matter?

Answer 25

• Solid: Fixed shape and volume, tightly packed particles. • Liquid: Fixed volume, no fixed shape, particles move past each other. • Gas: No fixed shape or volume, particles move freely.

Question 26

What determines the state of matter?

Answer 26

Temperature and pressure, which affect particle motion and arrangement.

Question 27

Define an atom.

Answer 27

The smallest unit of an element, consisting of protons and neutrons in the nucleus, and electrons orbiting the nucleus.

Question 28

What is the difference between an atomic number and mass number?

Answer 28

• Atomic Number: Number of protons (or electrons in a neutral atom). • Mass Number: Total number of protons and neutrons.

Question 29

What is an isotope?

Answer 29

Atoms of the same element with the same number of protons but different numbers of neutrons.

Question 30

Define a molecule.

Answer 30

A neutral group of two or more atoms bonded covalently.

Question 31

Can all molecules be compounds?

Answer 31

No. Molecules can consist of the same element (e.g., O₂), but compounds must have different elements (e.g., H₂O).

Question 32

What are ions?

Answer 32

Atoms or molecules that become charged by gaining or losing electrons (e.g., Na⁺, Cl⁻).

Question 33

What is a chemical formula?

Answer 33

A representation of the types and numbers of atoms in a compound (e.g., NH₃ for ammonia).

Question 34

Explain the use of brackets in chemical formulas with an example.

Answer 34

• Brackets indicate grouping in formulas. • Example: Mg(OH)₂ means one magnesium, two oxygen, and two hydrogen atoms.

Question 35

Name and symbol of the first five elements in the periodic table?

Answer 35

1. Hydrogen (H) 2. Helium (He) 3. Lithium (Li) 4. Beryllium (Be) 5. Boron (B)

Question 36

Why do atoms form chemical bonds?

Answer 36

To increase stability and lower potential energy.

Question 37

What are valence electrons?

Answer 37

Electrons in the outermost shell of an atom that participate in bonding.