Introductory Chemistry – Lecture 1: Matter, Energy, and the Scientific Method

Thirty Q&A flashcards summarizing core ideas on matter, mixtures, states, changes, energy, and the scientific method from Kevin Revell’s Introductory Chemistry lecture.

In what wide-ranging fields can chemistry be applied?

Agriculture, environmental science, biology/medicine, geology, physics, engineering, and materials science.

What is the smallest unit of an element that retains the identity of that element?

An atom.

What is an element?

A pure substance composed of only one kind of atom.

How is a compound defined in chemistry?

A pure substance composed of two or more different elements chemically bonded together.

What is a molecule?

Two or more atoms chemically bonded; can be of the same or different elements.

What distinguishes a pure substance from a mixture?

A pure substance has a fixed composition (element or compound), while a mixture contains two or more substances physically combined.

What is a homogeneous mixture?

A mixture whose components are evenly blended throughout (uniform composition).

What is a heterogeneous mixture?

A mixture whose components are not evenly blended and remain physically distinct.

Give one common method used to separate mixtures.

Filtration, distillation, chromatography, or decanting (any correct method earns credit).

Name the three common physical states of matter.

Solid, liquid, and gas.

How are the particles arranged in a solid?

Particles are closely packed in fixed positions with only vibrational motion.

How are the particles arranged in a liquid?

Particles are close together but can move past one another, giving the liquid a definite volume but no fixed shape.

How are the particles arranged in a gas?

Particles are far apart and move independently, giving the gas no fixed shape or volume.

Why is a phase change considered a physical change?

Because the substance’s identity is unchanged; only its physical state alters.

Define a physical property.

A characteristic that can be observed or measured without changing a substance’s chemical identity.

Define a chemical property.

A characteristic that describes a substance’s ability to undergo a change that transforms it into a different substance.

What is a physical change?

A change that alters only the form or appearance of matter, not its chemical composition.

What is a chemical change?

A change in which one or more substances are converted into different substances with new compositions and properties.

When zinc and sulfur combine to form zinc sulfide, what type of change occurs?

A chemical change.

State the law that describes energy’s tendency regarding stability.

Systems tend to move from higher energy to lower energy, releasing energy in the process.

What is energy?

The capacity to do work or produce heat.

Differentiate between potential and kinetic energy.

Potential energy is stored energy due to position or composition; kinetic energy is energy of motion.

What is heat energy?

The transfer of thermal energy due to a temperature difference.

Define an exothermic change.

A process that releases energy to its surroundings, usually in the form of heat.

Define an endothermic change.

A process that absorbs energy from its surroundings.

Does photosynthesis store or release energy?

It stores energy by converting light energy into chemical potential energy in plant material.

What is a scientific hypothesis?

A tentative, testable explanation for an observation or phenomenon.

What is a scientific theory?

A well-substantiated explanation of some aspect of the natural world that can incorporate laws, hypotheses, and facts.

What is a scientific law?

A concise statement that describes a consistent, observable pattern in nature, often expressed mathematically.

List the basic steps of the scientific method.

Make observations, formulate hypotheses, test ideas with experiments, and refine or develop new ideas based on evidence.