(2015•广西)在“测量盐水的密度“实验中:(1)把天平放在 水平

2015广西)在测量盐水的密度实验中:

1)把天平放在 水平 桌面上,游码归零后,发现指针位置如图1所示,此时应将平衡螺螺母向 左 (选填)调节,直到横梁水平平衡:

2)将装有适量盐水的小烧杯放在天平的左盘上,天平平衡时,所用砝码和游码在标尺上的位置如图2所示,若小烧杯的质量为20g,则小烧杯中盐水的质进为 86 g.然后,将烧杯中的盐水全部倒入量简中,液面到达的位置如图3所示,则量简中盐水的体积为 60 cm3,由此可计算出盐水的密度为 1.1×103 kg/m3

3)此次实验操作测得的盐水密度值偏 小 (选填)原因是 量筒中的盐水不能全部倒入烧杯,测得盐水的质量偏小,但体积准确 

答案

           解:

1)天平使用时,要放在水平的桌面上;因为指针静止时指在标尺中央红线上的右测,所以将平衡螺母向左移动;

2)已知烧杯m1=20g,将盐水和烧杯的质量为m2=50g+20g+10g+5g+1g=86g

量筒中盐水的质量为m=m2m1=86g20g=66g

量筒中盐水的体积为V=60cm3

所以盐水的密度为ρ===1.1g/cm3=1.1×103kg/m3

3)量筒中的盐水不能全部倒入烧杯,测得盐水的质量偏小,但体积准确,由ρ=可知,密度偏小;

故答案为:(1)水平;左;(286601.1×103;(3)小;量筒中的盐水不能全部倒入烧杯,测得盐水的质量偏小,但体积准确.

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