Chemistry Basics

Chemical Properties and Substances

• The ability of a substance to undergo a chemical change is a chemical property.
• A chemical property is a characteristic of a substance that can be observed or measured during a chemical reaction.

Composition of Substances

• Water is a compound made up of different elements.
• A compound is a pure substance formed from chemical combinations of two or more different elements.

Types of Substances

• A pure substance that cannot be broken down into any other substances by any chemical means is an element.
• An element is a pure substance that consists of only one type of atom.

Measurement of Physical Quantities

• The measure of gravity on an object is its weight.
• Weight is different from mass, which is a measure of the amount of matter in an object.
• The amount of space matter takes up is called volume.
• Volume can be measured in units such as liters or cubic centimeters.

Units of Measurement

• Mass can be measured in units called grams.
• Volume can be measured in units such as liters or cubic centimeters.
• The liter and cubic centimeter are both units used to measure volume.

Chemical Reactions

• In an endothermic reaction, energy is absorbed in the form of heat, not released.

Chemical Properties and Changes

• Chemical property: the ability of a substance to undergo a chemical change
• Chemical change: a process that alters the chemical composition of a substance

Substances and Elements

• Compound: a pure substance formed from chemical combinations of two or more different elements
• Element: a pure substance that cannot be broken down into any other substances by any chemical means

Measurement and Properties

• Mass: a measure of the amount of matter in an object
• Weight: the measure of gravity on an object
• Volume: the amount of space matter takes up
• Density: mass per unit volume of a substance
• Units of measurement: grams for mass, liters or cubic centimeters for volume

States of Matter

• Solid: particles are tightly packed and vibrate; has a definite shape and volume
• Liquid: takes the shape of its container; has a definite volume but not shape
• Gas: expands to fill the space available to it; has neither definite shape nor volume

Physical Changes

• Physical change: alters the form of a substance, but does not change it into another substance
• Examples: changes in state (solid to liquid, liquid to gas, etc.)
• Melting: change from solid to liquid
• Freezing: change from liquid to solid

Chemical Changes

• Chemical change: a process that alters the chemical composition of a substance
• Examples: burning gasoline produces carbon dioxide, lighting a match
• Chemical reaction: a process that involves a chemical change

Energy and Matter

• Thermal energy: energy of the motion of particles in a substance
• Mechanical energy: energy of motion or position of an object
• Potential energy: energy of an object due to its position or configuration

Atomic Structure

• Atom: the central core (nucleus) consists of protons and neutrons, surrounded by electrons
• Proton: positively charged particle in the nucleus
• Neutron: neutral particle in the nucleus
• Electron: negatively charged particle outside the nucleus

Test your knowledge of basic chemistry concepts, including chemical reactions, substances, and properties. Answer questions about the definition of chemical properties, the composition of water, and the classification of substances.