Standards, curriculum and language are different layers
NGSS 2-PS1-2 asks learners to use evidence from materials tests to judge suitability for a purpose. This lesson contributes to that expectation; one activity does not establish mastery. Check your district's adopted curriculum and sequence.
Teacher Teahouse curriculum example: Grade 2 → Science → NGSS 2-PS1-2 → Materials around us → Keeping a paper figure dry. The curriculum topic and lesson below are original planning choices, not an official NGSS unit.
标准、课程与语言层分开设计
NGSS 2-PS1-2 关注学生根据材料测试的证据判断材料是否适合某种用途。本课支持这一要求，但一次活动不能证明完全达标。请结合学区采用的课程和进度。
教师茶社课程示例：二年级 → 科学 → NGSS 2-PS1-2 → 身边的材料 → 让小纸人保持干燥。这里的单元主题与课堂设计是原创备课示例，不是 NGSS 官方单元。
Set two clear targets
- Content: compare three tested materials and justify which best keeps the paper underneath dry under our test conditions.
- Mandarin: name a material, report an observation and give a reason for a choice.
- Language functions: predict, compare, explain and revise. Keep 'I think' before testing separate from 'I observed' afterward.
明确两个学习目标
- 内容目标：比较三种经过测试的材料，说明在本次条件下哪种更能让下面的纸保持干燥。
- 中文目标：说出材料名称，报告观察结果，并说明选择理由。
- 语言功能：预测、比较、解释、修正。区分测试前的“我觉得”和测试后的“我观察到”。
Prepare a safe, repeatable test
For each group, prepare equal-sized pieces of plain paper, paper towel and reusable plastic sheet; three identical cups; dry tissue squares; water droppers; a tray and a timer. Adults pre-cut materials. Use only small amounts of water, keep it away from devices, and wipe spills promptly.
Place a dry tissue inside each cup, secure one material across each opening, and label the cups A, B and C. Use the same dropper, number of drops, height and waiting time. Test beforehand so the setup is manageable. Repeat once with fresh dry pieces; do not turn an unexpected result into the 'correct' answer.
This model tests resistance to water reaching the tissue, not every quality a real shelter needs. It does not test wind, durability or structural strength.
准备安全、可重复的测试
每组准备同样大小的普通纸、纸巾和可重复使用的塑料片；三个相同杯子、干纸巾小块、滴管、水、托盘和计时器。材料由成人预先剪好。只用少量水，远离电子设备，及时擦干洒出的水。
每个杯子里放一块干纸巾，在杯口固定一种材料，标为 A、B、C。保持滴管、滴数、高度与等待时间相同。教师先试做，确认操作可行。换干材料再测一次；出现意外结果时不要改成预设的“正确答案”。
这个模型测试的是水是否到达下方纸巾，不代表真实雨棚的全部性能。它没有测试抗风、耐用程度或结构强度。
Give students a small working word bank
- 材料 cáiliào — material; 纸 zhǐ — paper; 纸巾 zhǐjīn — paper towel/tissue; 塑料 sùliào — plastic.
- 干 gān — dry; 湿 shī — wet; 吸水 xīshuǐ — absorb water; 漏水 lòushuǐ — leak; 证据 zhèngjù — evidence.
- Use material samples beside the words. Distinguish water absorbed by the top sheet from water reaching the tissue below. Students may point, draw or speak before writing.
给学生一组够用的词
- 材料 cáiliào — material；纸 zhǐ — paper；纸巾 zhǐjīn — paper towel/tissue；塑料 sùliào — plastic。
- 干 gān — dry；湿 shī — wet；吸水 xīshuǐ — absorb water；漏水 lòushuǐ — leak；证据 zhèngjù — evidence。
- 把实物放在词语旁。区分上层材料吸水与水到达下方纸巾；允许学生先指认、画图或口述，再写句子。
A 40-minute classroom sequence
- 0–5 minutes: show the paper figure and ask 哪种材料能让它保持干燥？ Students predict privately, then tell a partner.
- 5–10: model the test and a record with columns 材料 / 第一次观察 / 第二次观察 / 我的选择. Explain which conditions stay the same.
- 10–23: pairs test and switch roles: one adds water, one observes and records; then swap for the repeat. Record dry/wet patches with sketches or words rather than invented numerical scores.
- 23–31: compare results across pairs. If results disagree, inspect the setup and repeat one comparison before deciding.
- 31–37: students choose a material and defend it using their own records. Invite a partner to ask 你的证据是什么？
- 37–40: individual exit ticket: draw or name the chosen material and explain one observation. Collect a separate short Mandarin response.
40分钟课堂流程
- 0—5分钟：展示小纸人，问“哪种材料能让它保持干燥？”学生先独立预测，再与同伴交流。
- 5—10分钟：示范测试与记录表：材料 / 第一次观察 / 第二次观察 / 我的选择。说明哪些条件不能改变。
- 10—23分钟：两人合作，一人滴水，一人观察记录，第二轮交换。用图画或词语记录干湿范围，不编造数字评分。
- 23—31分钟：不同小组比较结果。如果观察不一致，先检查装置，再重测一组比较。
- 31—37分钟：学生依据自己的记录选择材料。同伴追问：“你的证据是什么？”
- 37—40分钟：独立离堂任务：画出或写出选择的材料，说明一条观察；另收一条简短中文表达。
Model talk without giving away the result
Original dialogue frame: A：你选哪种材料？ B：我选____。 A：为什么？ B：测试以后，下面的纸巾____，所以我选____。 A：两次都一样吗？ B：____。
For emerging speakers, offer 干 / 湿 picture cards and 我选____，因为____。 For more independent speakers, invite 虽然____，但是____ or 如果再测试，我会____。 Keep the evidence demand the same; vary language support, not the scientific goal.
示范交流，不提前给答案
原创对话框架：A：你选哪种材料？ B：我选____。 A：为什么？ B：测试以后，下面的纸巾____，所以我选____。 A：两次都一样吗？ B：____。
中文表达起步阶段可提供“干／湿”图卡和“我选____，因为____”。更独立的学生可用“虽然____，但是____”或“如果再测试，我会____”。保留同样的证据要求，只调整语言支持。
Read the evidence and plan tomorrow
Use two separate notes per learner. Science: did the student connect a choice to a recorded observation? Mandarin: could the student communicate that link independently, with a frame, or with pointing and teacher support? A limited sentence is not automatically limited science understanding.
Exit prompt: 我选____。我的证据是____。If students confuse prediction with observation, repeat the comparison with a clear before/after chart. If reasoning is sound but expression is difficult, keep the science moving and rehearse one explanation pattern.
Extension: change the purpose to cleaning up a small spill. Would the same material still be best? Ask for a new test rather than transferring the previous answer. No student personal data or AI tool is needed.
看懂证据，再决定下一课
每名学生分开记录两项：科学方面，能否把选择与记录的观察联系起来；中文方面，能否独立表达、借助句框表达，或需要指认与教师支持。句子短不等于科学理解弱。
离堂提示：“我选____。我的证据是____。”若学生混淆预测与观察，下一课用测试前后对照表重做比较；若推理清楚但表达困难，保留科学进度，集中练一个解释句式。
延伸问题：如果任务变成擦掉一小滩水，原来的材料还是最好的吗？要求重新测试，而不是直接沿用上次答案。活动无需学生个人信息，也无需 AI 工具。