为测定碳酸钙纯度(设所含杂质为SiO2),同学们设计了如下两个实验方案: 【方案I】 (1)组装发生并测定生成气体体积的实验装置,并检验气密性; (2)称取碳酸钙样品W g; (3)加入过量盐酸; (4)收集并测定生成的气体体积V mL。 问题I—1:如果称量样品时,砝码底部有一处未被实验者发现的残缺,那么测定的碳酸钙的纯度会 (填“偏高、偏低、无影响”)。 问题I—2:在方 运动前的热身活动有助于肌肉放松,也能避免受伤。请阅读1-5题有关热身活动的文字,然后从A、B、C、D和E中选择符合文字内容的图示,并将答案写在对应题号的横线上。 1. Activity 1 ◇ Hold arms straight out to the siders ◇ Move your arms in circles. ◇ Come back to the starting position and move your arms in the other direction. 2. Activity 2 ◇ Raise one foot backward, and hold it with one hand. ◇ Breathe and slowly pull your foot to your hip(屁股). ◇ Try to keep both knees together. 3. Activity 3 ◇ Stand with some space in front of and behind you.Move the top of your body downward. ◇ Keep your back straight and reach for your feet with both hands. ◇ Hold this for about half a minute. 4. Activity 4 ◇ Take one step forward with your right foot. ◇ Put your hands on the right knee and press(压). ◇ Do the action in the same way with your left foot. 5. Activity 5 ◇ Stand with feet shoulder-width apart(两脚与肩同宽). ◇ Raise both arms overhead. ◇ Hold for about half a minute and relax.