A lesson in a lab
Do you have such an experience to do an experiment with the help of a teacher?
You will hear a conversation in which a teache
r helps a student do an experiment. Can you predict the result according to the aim?
Listen to the conversation and complete the description of the scientific experiment.
Aim: to find out if there’s a change in weight when magnesium burns in air. Apparatus: Magnesium, Bunsen burner, a balance, a crucible.
Method: First, put the magnesium in the crucible.
Then put the crucible on the balance and weigh it.
Next, heat the magnesium. Light the Bunsen burner and hold the crucible over it.
Finally, weigh the magnesium again.
It weighs a little more than before.
Conclusion: There is a change in weight when magnesium burns in air.
A.先说“几十”， 再说“几”。如： 23— twenty-three 89— eighty-nine B. 先说“几百”， 再加and,再加末两位数 （或末位数）。如： 223— two hundred and twenty-three 416— four hundred and sixteen 809— eight hundred and nine
C. 1,000以上的数先从后向前数，每三位数加一 “,”（千分位）；第一个“,”号前为thousand; 第 二个“,”号前为million; 第三个“,”号前为billion。 如： one thousand and one 1,001— four thousand 4,000— nine thousand, seven hundred and 9,743— forty-three a (one) hundred and seventy-four 174,301— thousand, three hundred and one seven hundred and fifty million 750,000,000—
序数词一般以与之相应的基数词加词尾-th 构成，如：tenth（第十）。但下面这些基 数词在变序数词时， 有特别的地方。如：
one — first two — second three— third five— fifth eight — eighth nine— ninth twelve— twelfth
分子用基数词,分母用序数词;分子大于1 时, 分母的序数词后需要加s。
1/5 1/7 4/7 7/10 97/111
ninety-seven one hundred
4. 小数的读法 小数点读作 point
0.5 0.76 1.23 point five point seven six one point two three twenty-three point four five
5.百分数的读法 27% — twenty-seven percent
45% — forty-five percent 86% — eighty-six percent
Can you say the following in English correctly?
1,000 one thousand
one hundred and twelve thousand 796,000 seven hundred and ninety six thousand
nine hundred and eighty-eight million, seven hundred and sixty-six thousand, six hundred and eighty-eight
nine hundred and eighty-seven million, six hundred and fifty-four thousand, three hundred and twenty-one
Now let’s say: 2/5 5/8 9/10 3/8 5/6 two-fifths five-eighths
Read these questions aloud and say the answers.
1. What is ? of 6,000,000? Three million. 2. How much is 35,246,000 plus 12,800,000? Forty-eight million, forty-six thousand. 3. What is 25% of 200,000,000? Fifty million.
4. How much is 260,408,396 and 5,284,700? Two hundred, sixty-five million, six hundred, ninety-three thousand, ninety-six. 5. What is ? of 1,000,500,000? Seven hundred, fifty million, three hundred, seventy-five thousand. 6. What is 10% of 800,000,000? Eighty million.
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