Chapter 1 Energy

What are condensed phases?

Liquids and solids are called condensed phases because their molecules are closely packed compared to gases, which are less dense.

What is the difference between pure substances and mixtures?

Pure substances contain only one type of element or compound, while mixtures consist of multiple substances physically combined.

What are allotropes?

Allotropes are different structural forms of the same element, such as diamond, graphite, and C₆₀ (buckminsterfullerene) for carbon.

Why are diamond and graphite different?

Although both made of carbon, diamond has a stable, 3D structure that makes it hard and durable, while graphite has layers that slide easily, making it soft.

What are protons, neutrons, and electrons?

Protons are positively charged, neutrons have no charge, and electrons are negatively charged. Together, they make up the structure of an atom.

What does it mean for an atom to be neutral?

: An atom is neutral when it has the same number of protons and electrons, balancing positive and negative charges.

What are isotopes?

Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons.

What are examples of elements over and under mass number 50?

Iron (Fe) has a mass of 55.845 and is vital for red blood cells. Neon (Ne) has a mass of 20.18 and is rare on Earth but abundant in the universe.

What is the relationship between cellular respiration and photosynthesis?

What is the relationship between cellular respiration and photosynthesis?

Why isn’t 100% oxygen safe to breathe?

Pure oxygen is highly reactive and would damage body tissues and lungs due to excessive combustion-like chemical reactions

What are the main layers of the atmosphere?

Troposphere (where life exists), Stratosphere (contains ozone layer), Mesosphere, Thermosphere (satellites), and Exosphere (outermost).

What is particulate matter (P

PM refers to solid or liquid particles suspended in air. PM2.5 is especially dangerous because it can penetrate deep into the lungs.

What are common air pollutants?

: Carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (SOx), ozone (O₃), particulates, and lead.

What does “ppm” and “ppb” mean?

PM means parts per million, and PPB means parts per billion — both measure the concentration of a gas or pollutant in air.

What is the difference between complete and incomplete combustion?

Complete combustion occurs with enough oxygen, producing CO₂ and H₂O. Incomplete combustion occurs with limited oxygen, producing CO and soot.

What is a chemical reaction?

A chemical reaction involves breaking and forming bonds between atoms, resulting in new substances.

What are aliphatic hydrocarbons?

Aliphatic hydrocarbons are simple compounds made of hydrogen and carbon, such as methane (CH₄) and propane (C₃H₈).

Why is balancing chemical equations important?

It ensures the conservation of mass — atoms cannot be created or destroyed, so each element must appear equally on both sides.

What are the three main types of ultraviolet radiation?

UVA (least energetic, reaches Earth), UVB (partially blocked by ozone), and UVC (most energetic, absorbed by ozone layer).

What is radiation?

Radiation is energy that travels through space as electromagnetic waves or high-speed particles, including light, UV, and gamma rays.

What is the relationship between wavelength and frequency?

Wavelength and frequency are inversely related — as wavelength decreases, frequency and energy increase (λν = c).

What is Planck’s constant?

Planck’s constant (6.626 × 10⁻³⁴ J·s) relates the energy of a photon to its frequency; higher frequency means higher energy.

Which electromagnetic waves are most and least energetic?

Gamma rays are the most energetic, while radio waves are the least. Visible light lies in between.

What are the main components of sunlight reaching Earth?

53% infrared, 39% visible light, and 8% ultraviolet radiation

What is the ozone layer and why is it important?

The ozone layer in the stratosphere absorbs harmful UV radiation, protecting living organisms from DNA damage.

What causes the ozone hole?

In Antarctica, cold conditions form polar stratospheric clouds that catalyze ozone depletion, especially when CFCs release chlorine atoms.

What are Dobson Units (DU)?

Dobson Units measure the thickness of the ozone layer. 100 DU equals 1 mm of pure ozone gas at ground-level pressure.

What is the Chapman Cycle?

It describes the natural creation and destruction of ozone through reactions involving oxygen molecules and UV radiation.

What are valence electrons?

Valence electrons are the outermost electrons involved in chemical bonding; atoms bond to achieve full outer shells (octet rule).

What is the octet rule?

Atoms are most stable when they have eight electrons in their outer shell, leading to chemical bonding that fills these shells.

: Why do atoms form bonds?

Atoms bond to lower their energy and achieve stable electron configurations, often by sharing or transferring valence electrons.

What are radicals?

Radicals are highly reactive species with unpaired electrons, often formed when radiation breaks molecular bonds.

How do CFCs affect the ozone layer?

Chlorofluorocarbons release chlorine atoms that catalyze ozone destruction in the upper atmosphere, thinning the protective layer.