问题
问答题
设计方案证明Zn的活动性比铜强。（要求写明操作、现象和结论）
答案
取锌片放入硫酸铜溶液 中一会取出，锌的表面出现红色固体，说明锌的活动性比铜强。（或分别取两种金属，投入稀盐酸中，锌的表面有气泡产生、铜的表面没有明显变化，说明锌的活动性比铜强。）
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设计方案证明Zn的活动性比铜强。（要求写明操作、现象和结论）
取锌片放入硫酸铜溶液 中一会取出，锌的表面出现红色固体，说明锌的活动性比铜强。（或分别取两种金属，投入稀盐酸中，锌的表面有气泡产生、铜的表面没有明显变化，说明锌的活动性比铜强。）
Work your brain! Between 2 and 3 pounds of wonder，it controls everything we say，do or think，who we are and what we care about. The way we walk or laugh or figure out things. What we like and the talents we possess. How we see and talk and run and jump and process our food. The brain uses 20 percent of our body's oxygen and 20 percent of its blood. Somewhere within its protein，fat, 100,000 miles of blood vessels and 100 billion nerve cells，it helps us remember where we put our gym shoes. Change our temperature so we don't die because of the heat or cold. Speed us up or slow us down. Help us choose between orange juice or orangeflavored drinks. Its intricacies(复杂性)are stunning，far beyond anything most of us can imagine. To keep this work of art as polished(有光泽的) as possible we need to eat right，exercise and keep mentally stimulated(刺激)． Good nutrition helps brain cells communicate with each other. Exercise stimulates a hormone(荷尔蒙)in our brain that improves memory. Mental stimulation keeps you sharp even as you age. “It's very important that we tell people to be physically active and mentally active，” said neurologist Malcolm Stewart. “People cannot stop aging，but you're able to reduce the damage；you're able to keep the function up.” Following are Dr.Stewart's advice for improving brain health：
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