University:
High School
Course:
High School Chemistry
Academic year:

2025
Views:

56

Pages:

1
Author:

Rajan Patel

1. What is Chemistry? Chemistry is the study of matter—what it's made of, how it behaves, and how it changes during chemical reactions. 2. Atoms and Elements: ● Atom: The smallest unit of matter. ● Element: A pure substance made of one type of atom (e.g., oxygen, carbon, gold). ● Periodic Table lists all known elements. 3. Molecules and Compounds: ● Molecule: Two or more atoms bonded together (e.g., O₂). ● Compound: A substance made of two or more different elements (e.g., H₂O, CO₂). 4. States of Matter: ● Solid: Definite shape and volume. ● Liquid: Definite volume, no fixed shape. ● Gas: No fixed shape or volume. 5. Chemical Reactions: ● Substances change into new substances. ● Signs: color change, temperature change, gas production, precipitate (solid) formation. 6. Basic Particles: ● Protons: Positive charge, in nucleus. ● Neutrons: No charge, in nucleus. ● Electrons: Negative charge, orbit nucleus. 7. Law of Conservation of Mass: Mass is neither created nor destroyed in a chemical reaction—total mass stays the same.