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18. Penny: Used to measure mineral toughness; Cuprum penny's toughness is 3.

Hand Lens: Could be used to measure the hardness of the mineral; the glass can be used as a scratch platform; it can also be used to test the luster of the mineral tile; the mineral is rubbed in the glass portion of the tile and a powdery strike of the stone is given to distinguish the colour of the rock.

Geological hammer: Used to break down the mineral to assess whether or not it has cleavage, and to detect fractures

Pocketknife: Used to define mineral tenacity; the tenacity of the mineral can be silky, malleable, sectile, elastic, or flexible.

17. Volcanoes are holes or cracks in the lava-flowing crust of the earth. They are normally placed on the borders of tectonic plates as they are created as the plates clash and create gaps. In other words, volcanoes located at convergent-plate boundaries.

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the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.

because the light is a great source of energy for the plants to survive. (i hope this )