8h rocks (chemistry)

Question 1

chemical, biological + physical weathering definitions

Answer 1

• chemical weathering = when acidic rain water reacts with minerals in the rock
• physical weathering = when rocks are weathered due to temperature changes
• onion-skin weathering = when minerals in a rock expands from heat and contracts from the cold, producing strong forces, causing the rock to crack
• freeze-thaw action = when water gets into a crack and expands when it turns into ice, making the crack wide
• biological weathering = when rocks are broken up or worn away by plants and animals

Question 2

intrusive vs. extrusive + igneous vs. metamorphic

Answer 2

• extrusive = rocks formed on the surface from lava
• intrusive = rocks formed from magma that solidified and cooled from within the crust
• metamorphic = rocks formed from other rocks that are changed by heat + pressure underground (e.g. marble)
• igneous = rocks formed from solidified magma or lava deep inside the earth ( e.g. granite)
• lava = magma emerged from underground (extrusive igneous rocks)

Question 3

erosion + sediments definitions

Answer 3

• erosion = when rocks are broken up by weathering where their fragments are moved by water, wind or ice
• sediments = bits of rock or sand in streams or rivers

Question 4

sedimentary rocks process

Answer 4

1. when moving water or air slows down, it deposits any sediments it is transporting
2. some get moved again, but some form layers
3. compaction = the newer/higher layers squash the bottom layers
4. compaction squeezes out the water out from the gaps between the grains
5. cementation = when dissolved minerals in the water crystallise in the gaps, forming a ‘glue’ that sticks the grains together

Question 5

grains + minerals definition

Answer 5

• rocks are made out of grains
• minerals = the chemical compounds that make up rocks

Question 6

types of rock: sedimentary, igneous + metamorphic (examples, grains or crystals?, hard or soft?, porous)

Answer 6

sedimentary:
* e.g. limestone, sandstone, mudstone and chalk
* separate grains
* often soft or crumbly
* often porous
igneous:
* e.g. basalt, gabbro and granite
* interlocking crystals that are not lined up
* hard
* not usually porous
metamorphic:
* e.g. marble, quartzite, slate, schist, gneiss
* interlocking crystals, often lined up in bands of different colors
* hard
* not usually porous

Question 7

porous, permeable, interlocking + impermeable definitions

Answer 7

• porous = rocks with round grains that can absorb water
• permeable = the round grains of rocks that let water flow through them
• impermeable = water cannot pass through the rocks
• interlocking = no space between them
• rocks with interlocking grains are usually hard, don’t wear away easily and are impermeable

Question 8

fossils

Answer 8

• fossils form when dead plants or animals fall to the bottom of the sea
• they don’t rot when their remains are covered in sediments
• sediments become sedimentary rocks and the organism’s shape is preserved as its hard parts turned into stone

Question 9

cement + concrete process + metals, ores + minerals

Answer 9

• cement is made from limestone
• concrete is made from mixing cement, gravel and sand with water
• gold and silver are unreactive metals
• ore = a rock with enough of a particular mineral to make it worth mining
• pure minerals are obtained from minerals using chemical reactions
• mining metals destroys habitats and causes pollution
• if we recycle we can make supplies of metal last longer, reduce mining and reduce pollution

Question 10

earth’s layers

Answer 10

1. crust
   * made out of solid rocks and minerals
2. mantle
   * made out of rocks or ices and is the thickest layer
3. outer core
   * (only liquid layer) made metals like iron and nickel
4. inner core
   * extremely hot and made out of iron and nickel (similar to the outer core)