部分氧化的Fe﹣Cu合金样品(氧化产物为Fe2O3、CuO)共5.76g,经如下处理:下列说法正确的是( ) A . 滤液A中的阳离子为Fe2+、Fe3+、H+ B . 样品中Fe元素的质量为2.24g C . 样品中CuO的质量为4.0g D . V=448 答案:B,D
We experience different forms of the Sun’s
energy every day. We can see its light and feel its warmth. The Sun is
the major source of evaporation (蒸发) of water from the oceans and lakes. Sunlight also provides the
energy used by green plants to make their own food. These green plants then
provide food for all organisms (生物) on the Earth.
Much of the energy that comes from the Sun
never reaches the Earth’s surface. It is either reflected or absorbed by the
gases in the upper atmosphere. Of the energy that reaches the lower atmosphere,
30% is reflected by clouds or the Earth’s surface. The remaining 70% warms the
surface of the planet, causes water to evaporate, and provides energy for the
water cycle and weather. Only a tiny part, approximately 0.023%, is actually
used by green plants to produce food.
Many gases found in the atmosphere actually
reflect heat energy escaping from the Earth’s surface back to the Earth. These
gases act like the glass of a greenhouse in that they allow energy from the Sun
to enter but prevent energy from leaving. They are therefore called greenhouse
gases.
When sunlight strikes an object, some of
the energy is absorbed and some is reflected. The amount reflected depends on
the surface. For example, you’ve probably noticed how bright snow is when
sunlight falls on it. Snow reflects most of the energy from the Sun, so it
contributes to the low temperatures of winter. Dark-coloured surfaces, such as
dark soil or forest, absorb more energy and help warm the surrounding air.
1.According to the passage, the root cause
for weather changes on the Earth is ______.
A.the atmosphere surrounding the Earth
B.water from oceans and lakes
C.energy from the Sun
D.greenhouse gases in the sky
2.Only a small part of the Sun’s energy
reaches the Earth’s surface because most of it _______________.
A.absorbed by the clouds in the lower atmosphere
B.reflected by the gases in the upper atmosphere
C.lost in the upper and lower atmosphere
D.used to evaporate water from the oceans and lakes
3.We learn from the passage that
_______________.
A.all living things on the Earth depend on the Sun for their food
B.a forest looks dark in winter because it absorbs solar energy
C.only 0.023% of the energy from the Sun is made use of on the Earth
D.greenhouse gases allow heat energy to escape from the Earth’s surface