____个

【查阅资料】

①
     2NaHCO₃ $\underset{\_}{\underset{\_}{\Delta }}$ Na₂CO₃+CO₂↑+H₂O

②NaHCO₃+NaOH=Na₂CO₃+H₂O

③2NaHCO₃+Ca（OH）₂=CaCO₃↓+Na₂CO₃+2H₂O

④Ca（HCO₃）₂+Na₂CO₃=CaCO₃↓+2NaHCO₃

⑤Na₂CO₃受热不分解，NaHCO₃、Ca（HCO₃）₂都能溶与水．

【假设猜想】

假设一：小苏打没有变质，化学成分为 NaHCO₃；

假设二：小苏打完全变质，化学成分为____；

假设三：小苏打部分变质，化学成分为____．

【实验方案】

可选药品：①Ca（OH）₂溶液     ②CaCl₂溶液      ③NaOH溶液    ④稀盐酸

【问题讨论】

有同学认为，取一定量样品直接加热，再将产生的气体通入澄清石灰水，根据实验现象，对上述三种假设的每一种是否成立都能进行判断．请评价这种方案是否合理____（填“是”或“否”），理由是____．

完形填空

    Things can become very dangerous in a fire. 1 will you do if you cannot get out of the room?

    If you cannot get out of the room, close the door and put blankets (毛毯) at the 2 of the door. They can 3 the smoke from coming in.

    And 4 119 for help. Then open the window and 5 for help. Wave (摇摆) a piece of cloth from the window. Let people know that you are still inside the room.

    Don't stay under the bed or in the wardrobe. When the firefighters come in, they will have to 6 you. So stay by the window.

    If your clothes 7 fire, remember the words: stop, drop and roll.

    Stop running. Moving around will make the fire even 8. Drop and lie down on the floor. Roll around, from one side to 9 to stop the fire.

    If your friend's clothes are on fire, don't let him or her 10. Shout, "Stop, drop and roll!" When he or she is rolling on the floor, you can use a blanket or other heavy cloth to help to put out the fire on his or her clothes.