Materials

Firewood is wood that has been collected just to be burnt as fuel. Firewood is usually cut into small pieces so it can fit inside a fireplace.

Foam is made up of a lot of small bubbles, usually found on the top of a liquid like the sea or a glass of beer.
Something that is full of bubbles may also be called foam, such as the foam padding found inside seat cushions.

When an animal or plant dies and is buried under the ground with the right conditions for thousands or even millions of years, it turns to stone. Later when we dig them back up, we call them a fossil. When something has been turned into a fossil it is fossilised.
People have found fossils of all sized creatures, from tiny sea snails, to frogs, right up to enormous dinosaurs. Most of the creatures that people find as fossils are extinct - you can no longer see a living animal of that kind.
The fossil in the picture is a trilobite.

Froth is a collection of tiny bubbles that makes a kind of soft foam. Froth is often found on the top of cappuccinos, and on the seashore.

Garnet is a group of related stones, the most popular of which is a deep red. Until the chemical composition was known, red semiprecious gemstones were called carbuncles.
Garnets have a particular chemical formula of two metals, usually calcium, magnesium or iron and aluminium, iron or chromium bound to silicon oxide - the general forumula is X3Y2(SiO4)3.

A gel is a type of solid that has some liquid properties too. Gels keep their shape like solids, but with enough time will flow like a liquid. A lot of common items are gels, like hair gel, toothpaste, jello, soft contact lenses and breast implants.

Gingham is a kind of woven fabric pattern, also called plaid and sometimes called checked, but it is not the same as a checkerboard pattern.

Granite is a common, very hard rock that is widely used for building things. It is formed from molten rock (magma) as it cools.
Granite has a coarse, crystalline structure and is a mix of many different minerals. Because its composition can vary so much, granite can be found in a huge variety of different colors.

Gravel is small stones, usually used for a decorative landscaping mulch or as an aggregate in building materials like concrete.

Hay is dried grass or other crops that has been stored to be fed to animals. Hay usually has the seed heads of the grass in it as well as just the stems and leaves. Hay is different to straw.