14 The black core of a pencil is referred to as pencil lead.Pencil lead is a non-metallic material which has a resistivity of 5.4 × 103 m at room temperatur e.(a) A piece of pencil lead has a length of 15 cm an
Look very carefully at the ends of the pencil. It is made of two strips (条) of wood. People glued them together after they put the black-lead in.If you put it in water for a while, the glue will become soft (柔软的), and the two pieces of wood will come apart (分开). T...
The core of a pencil does not contain lead and never has. Pencils contain a form of solid carbon known as graphite. ... Since this writing material behaved similar to metallic lead, but had a darker color, people began calling it "black lead". Eventually, the name of the core of the ...
"Lead" pencils don't contain lead and aren't dangerous. Lead poisoning occurs when children or adults get lead into their body. Lead gets into the body by eating it or breathing it. According to the EPA, lead poisoning was once a major environmental health hazard. Is pencil lead pure gra...
Hackett, Regina
Aloe vera, peace lilies and spider plants are some of the species that are easy to grow indoors. You can buy plants from supermarkets, garden centres or online. Younger plants are often cheaper than fully grown ones, and you get to care for ...
Questions 41 to 44 are based on the following passage:The lead pencil is one of the most used pieces of merchandise in the world. It is the simplest, most convenient and least expensive of all writing instruments.Perhaps the most surprising thing about the lead pencil is that it is not le...
【题目】 Paper was first made in the year 105. It was made by a Chinese named Cai Lun. People in Japan learned of paper around the year 600. As years went by, people in other places began to make paper. The lead(铅) pencil is not made of lead. It is made of...
I chewed on my pencil. Aha! What if talking were the first step towards life as a criminal? Without the education I was throwing away, I’d turn to theft and go to prison. When I got out, people would say, “She used to talk in...
The soft core of a pencil is also sometimes referred to as lead, even though it’s made out of graphite and doesn’t usually contain lead: The lead in this pencil is too soft. Examples of led “As she led us up four flights of narrow stairs, she mentioned that the building was nine...