Chemistry

1. States of Matter

What are Solids, Liquids, and Gases?

Solids: Have a fixed shape and volume. The particles are packed tightly together and only vibrate in place. Examples: ice, rocks, metals.

Liquids: Have a fixed volume but no fixed shape. They take the shape of their container because the particles can slide past each other. Examples: water, milk, oil.

Gases: Have no fixed shape or volume. They spread out to fill any container because the particles move freely and quickly. Examples: air, steam, carbon dioxide.

Changes of State:

Melting: Solid to liquid (e.g., ice melting into water).

Freezing: Liquid to solid (e.g., water freezing into ice).

Boiling: Liquid to gas (e.g., water boiling into steam).

Condensation: Gas to liquid (e.g., water vapor condensing into dew).

Sublimation: Solid to gas without becoming a liquid first (e.g., dry ice turning into carbon dioxide gas).

2. Atoms, Elements, and Compounds

What are Atoms? Atoms are the smallest particles that make up everything around us. They are like tiny building blocks that are too small to see with your eyes.

Elements: Substances made of only one type of atom. Examples: Oxygen (O), Carbon (C), and Gold (Au).

Compounds: Substances made by chemically bonding two or more different elements together. For example, water (H₂O) is made of hydrogen and oxygen atoms.

Molecules: Groups of two or more atoms bonded together. For example, a molecule of oxygen is O₂, meaning two oxygen atoms are bonded together.

3. Chemical Reactions

What is a Chemical Reaction? A chemical reaction is when substances change into new substances. This can involve changes in color, temperature, or the formation of a gas.

Types of Chemical Reactions:

Exothermic Reactions: Reactions that release heat. For example, burning wood releases heat and light.

Endothermic Reactions: Reactions that absorb heat from their surroundings. For example, when you dissolve certain salts in water, the solution gets colder.

Oxidation: This is when a substance reacts with oxygen. Rusting is a form of oxidation where iron combines with oxygen to form rust.

Combustion: The process of burning. For example, when fuel burns in a car engine, it combines with oxygen and releases energy.

4. Acids, Alkalis, and the pH Scale

Acids: Substances with a pH less than 7. They taste sour and can be corrosive. Examples: vinegar and lemon juice.

Alkalis (Bases): Substances with a pH greater than 7. They feel slippery and can also be corrosive. Examples: soap and baking soda.

Neutral: Substances with a pH of exactly 7, like pure water.

Neutralization: When an acid and an alkali react together to form a neutral substance, usually resulting in water and a salt.