Chemistry Basics Quiz

Chemistry Basics

• Chemistry involves the study of matter and energy.
• Matter is defined as anything with mass that occupies space.

Elements and Substances

• Approximately a hundred elements comprise all matter on Earth, which are the simplest forms of matter.
• Elements cannot be chemically broken down into simpler substances and serve as the building blocks of the universe.
• Pure substances include elements and compounds; both have distinct properties and definite compositions.

Atoms and Bonds

• An atom is the smallest unit of an element maintaining its chemical properties.
• Chemical bonds form attractions between atoms of different elements, allowing them to combine or separate into new configurations.

Mixtures and Solutions

• Mixtures consist of two or more pure substances that are physically combined without chemical bonding and can be separated physically.
• Mixtures can be heterogeneous (not uniformly mixed) or homogeneous (uniform composition), also called solutions.
• Aqueous solutions contain water as the primary component.

Pure Substances Examples

• Elements: Hydrogen, sodium
• Compounds: Water, table salt
• Heterogeneous mixture examples: Oil and water, chicken noodle soup
• Homogeneous mixture examples: Brass, vodka

Properties of Substances

• Every substance has a unique set of properties that can identify it.
• Physical properties describe a substance without changing its composition (e.g., color, melting point).
• Chemical properties indicate how a substance reacts chemically.

Extensive vs. Intensive Properties

• Extensive properties, such as mass and volume, depend on the amount of substance present.
• Intensive properties remain constant regardless of the amount (e.g., density, color, melting point).

Chemical Changes and Reactions

• Chemical changes alter the chemical structure of substances through the formation or breaking of bonds.
• Reactants are starting materials, and products are formed substances after a reaction.

Energy

• Energy is defined as the capacity to do work and exists in multiple forms (e.g., chemical, thermal).
• Energy can be transformed but cannot be created or destroyed.

Scientific Method

• The scientific method encompasses observation, hypothesis formation, and experimentation.
• A hypothesis is an initial explanation based on observations, which is tested through experiments.

Theories and Laws

• Theories explain and predict phenomena based on collective observations; they are widely accepted within scientific communities.
• Scientific laws describe consistent observations without delving into the underlying explanations.

Law of Conservation of Mass

• Total mass before and after any physical change or chemical reaction remains constant, illustrating the law of conservation of mass.

Conceptual Clarifications

• A hypothesis becomes a theory after extensive testing without contradictions.
• A scientific law is an established truth observed repeatedly that lacks explanation.