Science Chapter: Matter and Its States

Matter

• Matter is anything that has mass and takes up space.
• Matter is made up of tiny particles called atoms.
• Atoms are the basic building blocks of all matter.
• Atoms of the same type make up chemical elements.
• Different atoms combine to form molecules.
• Molecules are groups of two or more atoms held together by chemical bonds.
• Different arrangements of atoms form different substances.

States of Matter

• Matter exists in three main states: solid, liquid, and gas.
• Solids: have a definite shape and volume. Particles are tightly packed and vibrate but do not move around.
• Liquids: have a definite volume but take the shape of their container. Particles are closely packed but can move past each other.
• Gases: have neither a definite shape nor a definite volume. Particles are widely spread and move freely in all directions.

Physical Changes

• Physical changes alter the form of a substance but do not change its chemical composition.
• Examples include melting, freezing, boiling, evaporating, dissolving, and condensing.
• Physical changes are usually reversible. For example, water can be frozen and then melted back into liquid water.

Chemical Changes

• Chemical changes result in the formation of new substances with different properties.
• Chemical reactions involve breaking and forming chemical bonds between atoms.
• Examples include burning, rusting, and reacting an acid and a base.
• Chemical changes are not easily reversed.

Properties of Matter

• Physical properties describe the characteristics of a substance that can be observed or measured without changing its chemical composition.
• Examples include color, odor, density, melting point, boiling point, and texture.
• Chemical properties describe how a substance reacts with other substances.
• Examples include flammability, reactivity with water, and acidity.

Elements

• Elements are pure substances that cannot be broken down into simpler substances by chemical means.
• Elements are organized in the periodic table.
• Each element has a unique symbol that represents it.

Compounds

• Compounds are pure substances formed when two or more elements chemically combine in a fixed proportion.
• Compounds have different properties than the elements from which they are formed.
• Compounds have a chemical formula that represents the elements present and their ratios.

Mixtures

• Mixtures are combinations of two or more substances that are not chemically combined.
• Mixtures can be separated by physical methods.
• Examples include solutions, suspensions and colloids.

Atomic Structure

• Atoms are composed of protons, neutrons, and electrons.
• Protons have a positive charge, neutrons have no charge, and electrons have a negative charge.
• Protons and neutrons are located in the nucleus of the atom.
• Electrons orbit the nucleus in electron shells or energy levels.
• The number of protons in an atom determines its atomic number.
• The number of protons and neutrons in an atom determines its mass number.

Chemical Reactions

• Chemical reactions involve the rearrangement of atoms to form new substances.
• Chemical reactions are represented by chemical equations.
• Reactants are the substances that undergo change.
• Products are the new substances formed.
• Chemical reactions often involve energy changes (endothermic or exothermic).

Periodic Table

• The periodic table is a table that arranges all known chemical elements in rows (periods) and columns (groups).
• Elements in the same group have similar chemical properties.
• The periodic table is a valuable tool for predicting the properties of elements and understanding how they react.

Measurements

• Measurements are a vital part of chemistry.
• Common units for measurement include grams, kilograms (mass), meters, centimeters, and liters (volume) and degrees Celsius and Kelvin (temperature).
• Measurements must be precise and accurate. Accurate measurement requires careful identification of appropriate units, understanding of instruments and a knowledge of correct significant figures when reporting results.

Acids and Bases

• Acids are substances that release hydrogen ions (H+) when dissolved in water.
• Bases release hydroxide ions (OH–) when dissolved in water.
• The pH scale measures the acidity or basicity of a solution – a measure of the concentration of hydrogen ions.
• Strong acids and bases release many ions, weak acids and bases release a few.
• Acid-base reactions involve the transfer of hydrogen ions between reactants - a neutralization reaction.