18. <em>Penny</em>: Used to measure mineral toughness; <em>Cuprum</em> penny's toughness is 3.
<em>Hand Lens</em>: 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.
<em>Geological hammer</em>: Used to break down the mineral to assess whether or not it has cleavage, and to detect fractures
<em>Pocketknife</em>: 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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Jobs. Like a snow blowing company. They would not have that in Puerto Rico. But Canada might. Because they have a different enviornment.
Correct answer: D) From bacteria living in their roots
Nitrogen is an essential plant nutrients, but it is metabolically unavailable to higher plants and animals. It is available to some species of microorganism by biological nitrogen fixation in which nitrogen is converted to ammonia with the help of enzyme dinitrogenase.
The process of breaking apart the two atoms in a nitrogen molecule is called nitrogen fixation. Plant obtain the nitrogen they need from the soil which is already fixed by the bacteria and archae.
Example: <em>Azobacter</em><em>,</em> Nostac