Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 344 · 40 questions

What you do (Heat shows the secret): 1. Dip a cotton bud in lemon juice and write a secret message on white paper. 2. Let the paper dry completely — the writing disappears. 3. An adult irons the paper on a low setting while you watch from a safe distance. 4. Read the brown message and wash your hands.

1. 1.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
2. 2.True or false: plugging in the iron is a job for an adult. (a) False (b) True
3. 3.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
4. 4.True or false: letting the paper dry is a job a child can do. (a) True (b) False
5. 5.True or false: turmeric powder is needed for the secret lemon message. (a) False (b) True
6. 6.True or false: writing the message is a job for an adult. (a) False (b) True
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) how dark the writing is (b) the same cotton bud (c) the kind of juice (d) the iron setting
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the same cotton bud (c) the ironing time (d) the iron setting
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we measure it (c) we keep it the same
10. 10.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) a mirror (d) an adult with an iron
11. 11.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) only an adult (d) the youngest child
12. 12.True or false: yeast is needed for the secret lemon message. (a) False (b) True
13. 13.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the ironing time (b) how dark the writing is (c) the kind of juice
15. 15.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) it gets darker (c) writing turns green (d) the paper floats
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we change it (c) we keep it the same
17. 17.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
18. 18.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
19. 19.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) lemon juice (c) a cotton bud (d) a balloon
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) False (b) True
21. 21.True or false: writing the message is a job a child can do. (a) False (b) True
22. 22.🔍 Which is the odd one out? (a) reading the message (b) putting the iron away (c) ironing the paper (d) cutting the lemon
23. 23.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) False (b) True
25. 25.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) True (b) False
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a cotton bud (c) a mirror (d) white paper
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) True (b) False
29. 29.True or false: white paper is needed for the secret lemon message. (a) False (b) True
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the kind of juice (c) the same paper
31. 31.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) no, it stays brown (d) yes, in the dark
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False
33. 33.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is magnetic (c) it can burn skin (d) it is cold
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) False (b) True
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we measure it (c) we change it
36. 36.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a battery cell (c) lemon juice (d) a mirror
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) an adult with an iron (d) a battery cell
38. 38.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) white paper (c) a cotton bud (d) a small bowl
39. 39.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) white paper (c) a cotton bud (d) turmeric powder
40. 40.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it

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