Matter and Reactions

In a chemical reaction, substances called reactants are transformed into new substances called products. The total mass stays the same because atoms are rearranged, not created or destroyed.

Temperature measures how fast particles are moving. At absolute zero, particles have the least possible energy. Heating matter increases particle motion and can cause state changes.

Thermal energy transfers from warmer objects to cooler ones through conduction (direct contact), convection (fluid movement), and radiation (electromagnetic waves).

Metals are generally shiny, conduct heat and electricity, and can be bent without breaking. Nonmetals are often dull, poor conductors, and brittle in solid form.

Crystallization occurs when a solution becomes supersaturated and dissolved particles form an orderly solid structure. Snowflakes, salt crystals, and rock candy form this way.

Elements are pure substances made of only one type of atom. Compounds are substances made of two or more elements chemically bonded in fixed ratios.

Solubility describes how much of a substance can dissolve in a solvent at a given temperature. Most solids dissolve better in hot water, while gases dissolve better in cold water.