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Practice Listening: Highlight Correct Summary
ID: #33201
Medium
IT
Transcript:
IT s common sense that some objects are harder than others. We refer to this characteristic as hardness, but what exactly is hardness? Let me tell you it's the ability of a material to resist being damaged, scratched, or marred in any way. There’s even a way to measure IT. IT's the most scale of hardness. A german scientist, urn., a meteorologist named fredrick, most came up with the scale in eighteen twelve. Here's how we made it. Most took ten different minerals, then he rated them from one to ten based on their ability to withstand damage and to damage other materials. Tell received a rating of one. IT's soft.. IT's easily scratched, can hardly damage anything. Diamond received a rating often. IT is the hardest natural substance known to man. The other objects on this scale, that number from two to nine are gypsum, calcite, fluoride, appetite, feldspar, quartz, topaz, and corundum. I see worried looks on your faces. Don't worry about writing them down there. Listed on page two hundred and thirty four of your text. Take a look. Now, what about the hardness of other objects? Hm. It depends on which of the ten minerals can scratch them. For instance, your fingernails get a rating of two point five on the most scale.
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