Chemistry Class: Changes and Mixtures

Reversible Changes

• A change is reversible if the object can return to its original form.
• No new material is created in a reversible change.
• The object's appearance changes, but its composition does not.

Irreversible Changes

• A change is irreversible if the object cannot return to its original form.
• A new material is usually formed in an irreversible change.
• Irreversible changes are permanent.

Solutions

• A solution forms when two or more substances mix evenly.
• The substance dissolving is the solute.
• The substance the solute dissolves in is the solvent.
• Water is a universal solvent.
• Solute + Solvent = Solution (e.g., salt + water = salt water)

Mixtures

• A mixture is a combination of two or more substances without a chemical reaction.
• Mixtures can be separated by various methods like sieving, hand-picking.

Filtration

• Filtration separates mixtures of liquids and insoluble substances.
• Insoluble substances remain on the filter paper.
• The liquid passes through the filter paper and collects below.
• Examples include separating tea leaves from tea.

Evaporation

• Evaporation is used to separate a solid from a liquid in a solution.
• The liquid evaporates, leaving the solid behind.
• When two liquids completely dissolve in each other, they are called miscible liquids.
• Otherwise, they are called immiscible liquids.

Layers of the Earth

• Earth has layers: crust, mantle, core.
• Crust is the outermost hard layer, mostly covered by water, soil, sand and ice.
• Mantle is the layer beneath the crust, comprising around 80% of the Earth.
• Core has an inner (solid) and outer (molten) part, primarily composed of iron and nickel.

Igneous Rocks

• Igneous rocks form from cooled magma (molten rock).
• Magma can cool inside or outside the Earth.
• Common igneous rocks include granite, pumice, basalt, and obsidian.
• Granite is used in buildings, basalt in roads, pumice as a cleaning agent.

Sedimentary Rocks

• Sedimentary rocks form from the accumulation and cementing of sediments (rock fragments).
• Examples include limestone, conglomerate, sandstone, and shale.
• Limestone is used in construction and making lime.
• Sandstone is used in construction.

Metamorphic Rocks

• Metamorphic rocks form when igneous or sedimentary rocks change due to heat and pressure.
• Examples include slate, marble, schist, and quartzite.
• Slate is used for roofing and in gardens.
• Marble is used for buildings and sculptures.

Minerals

• Minerals are naturally occurring substances with a specific chemical composition and crystal structure.
• Some minerals have important uses in our daily lives, including construction, manufacturing, and jewellery.
• Examples include graphite (used in pencils), coal (fuel), gold (jewellery), silica (glass).

This quiz explores the concepts of reversible and irreversible changes, solutions, and mixtures. Test your understanding of how substances interact and the methods used to separate mixtures. Dive into the fascinating world of chemistry and distinguish between different types of changes and solutions.