（1）化学是在____ 层次上研究物质的组成、结构、性质及其变化规律的科学．

（2）2004年中国正式开展月球探测工程． 2010年10月1日“嫦娥二号”卫星成功发射（如图）．下列月球探测工程中的项目属于化学研究对象的是　____ 　．

a．遥测控制卫星的运行

b．提供登月宇航员食用的纯天然食品

c．制造卫星整流罩需要的耐高温隔热材料

（3）化学与生活密切相关．生活中的下列物质属于混合物的　____ 　（填序号）．

    I think Christmas (圣诞节) is one of the happiest times of the year. Everyone has a smile on their face. It's such a(n) ____for kids. They can't wait to open their gifts and play with their____. It's a nice time for their parents too. They can ____with their family and relax. Let's not forget the true meaning of Christmas.  It is not about ____ Christmas trees or the snowman. It's all about love for each other and ____around the world.

阅读下列材料：

如果我们规定一种运算为$\left|\begin{array}{cc}a& b\\ c& d\end{array}\right|$=ad﹣bc，例如：$\left|\begin{array}{cc}2& 4\\ 3& 5\end{array}\right|$=2×5﹣4×3=﹣2，请按照这种运算的规定，解答下列问题：

（1）若$\left|\begin{array}{cc}5& \frac{1}{x-3}\\ 2x& \frac{1}{x}\end{array}\right|$=﹣2，求x的值；

（2）当x满足什么条件时，﹣1＜$\left|\begin{array}{cc}x& x-3\\ 3& -2\end{array}\right|$≤4；