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【简答题】
为了探究燃烧需要哪些条件，他和同学们进行了以下探究活动： [提出问题]物质在什么条件下才能燃烧？ [猜想与假设]要有可燃物质；氧气或空气；温度要达到着火点…… [设计与实验]在500mL的烧杯中注入400mL 开水，并投入一小块白磷（甲），在烧杯上一片薄铜片，铜片一端放一干燥的红磷，另一端放一小块用滤纸吸去表面水分的白磷（乙）。已知白磷的着火点为40℃，红磷的着火点为240℃。 (1)实验时观察到的现象：白磷（甲）__________，白磷（乙）____________，红磷________； (2)用导气管对准烧杯中的白磷（甲），通入少量的氧气或空气，观察到_______________。 [结论与解释]白磷（甲）不燃烧而白磷（乙）燃烧，说明燃烧需要___________；白磷（乙）燃烧而红磷不燃烧，说明燃烧需要____________；白磷（甲）在通人空气后燃烧再次说明燃烧需要________。由此得出燃烧的条件是：①____________，②_______________，③_____________ ，且三个条件缺一不可。 [反思与交流]白磷与红磷相比，更容易着火燃烧的是_________；少量白磷应保存在_________中。
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举一反三
【判断题】科学与文化之间是完全隔离和区别开的。()
A.
正确
B.
错误
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【简答题】（1）已知椭圆C： x 2 a 2 + y 2 b 2 =1(a＞b＞0) 的离心率为 6 3 ，椭圆C上任意一点到椭圆两焦点的距离和为6．求椭圆C的方程； （2）直线l：y=kx+1与双曲线C：2x 2 -y 2 =1的右支交于不同的两点A、B．求实数k的取值范围．
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【简答题】Are you a compulsive spender，or do you hold on to your money as long as possible? Are you a bargain hunter? Would you rather use charge accounts than pay in cash? Your answers to these questions will ...
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【单选题】【C8】
A.
medium
B.
moderate
C.
temperate
D.
gentle
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【单选题】If the supply of money is greater than the amount of money people want to hold, then
A.
spending will increase and the price level will fall.
B.
spending will increase and the price level will rise.
C.
spending will increase and the rate of interest will rise.
D.
non of the above; the amount of money supplied is never greater than the amount people want to hold.
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【单选题】Are you a compulsive spender, or do you hold on to your money as long as possible? Are you a bargain hunter? Would you rather use charge accounts than pay cash.* Your answers to those questions will r...
A.
Because people can buy love with money.
B.
Because people spend money to express love.
C.
Because money is basic to love.
D.
Because when people express love, they must use money.
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【单选题】According to the passage, if incomes and prices rise together ______.
A.
money will hold its value
B.
inflation is still a trouble
C.
inflation will not be a problem
D.
businesses will be prosperous
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【简答题】已知椭圆方程为 x 2 6 + y 2 3 =1，则其离心率为______．
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【单选题】The wind is gentle. Gentle in this sentence should be translated as ______.
A.
轻柔的
B.
绅士的
C.
文雅的
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【单选题】People forgo interest and hold money:
A.
because they are required to.
B.
to reduce their transactions costs.
C.
because there are no substitutes for money.
D.
because banks are too risky.
查看完整题目与答案
相关题目：
【判断题】科学与文化之间是完全隔离和区别开的。()
A.
正确
B.
错误
查看完整题目与答案
【简答题】（1）已知椭圆C： x 2 a 2 + y 2 b 2 =1(a＞b＞0) 的离心率为 6 3 ，椭圆C上任意一点到椭圆两焦点的距离和为6．求椭圆C的方程； （2）直线l：y=kx+1与双曲线C：2x 2 -y 2 =1的右支交于不同的两点A、B．求实数k的取值范围．
查看完整题目与答案
【简答题】Are you a compulsive spender，or do you hold on to your money as long as possible? Are you a bargain hunter? Would you rather use charge accounts than pay in cash? Your answers to these questions will ...
查看完整题目与答案
【单选题】【C8】
A.
medium
B.
moderate
C.
temperate
D.
gentle
查看完整题目与答案
【单选题】If the supply of money is greater than the amount of money people want to hold, then
A.
spending will increase and the price level will fall.
B.
spending will increase and the price level will rise.
C.
spending will increase and the rate of interest will rise.
D.
non of the above; the amount of money supplied is never greater than the amount people want to hold.
查看完整题目与答案
【单选题】Are you a compulsive spender, or do you hold on to your money as long as possible? Are you a bargain hunter? Would you rather use charge accounts than pay cash.* Your answers to those questions will r...
A.
Because people can buy love with money.
B.
Because people spend money to express love.
C.
Because money is basic to love.
D.
Because when people express love, they must use money.
查看完整题目与答案
【单选题】According to the passage, if incomes and prices rise together ______.
A.
money will hold its value
B.
inflation is still a trouble
C.
inflation will not be a problem
D.
businesses will be prosperous
查看完整题目与答案
【简答题】已知椭圆方程为 x 2 6 + y 2 3 =1，则其离心率为______．
查看完整题目与答案
【单选题】The wind is gentle. Gentle in this sentence should be translated as ______.
A.
轻柔的
B.
绅士的
C.
文雅的
查看完整题目与答案
【单选题】People forgo interest and hold money:
A.
because they are required to.
B.
to reduce their transactions costs.
C.
because there are no substitutes for money.
D.
because banks are too risky.
查看完整题目与答案