Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 84 · 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.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) True (b) False
3. 3.⚖️ 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
4. 4.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
5. 5.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) white (c) blue (d) brown
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we change it (c) we keep it the same
7. 7.🔍 Which is the odd one out? (a) reading the message (b) writing the message (c) ironing the paper (d) dipping the cotton bud
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) a small bowl (d) a balloon
9. 9.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) turmeric powder (c) an adult with an iron (d) a balloon
10. 10.True or false: writing the message is a job a child can do. (a) True (b) False
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we keep it the same (c) we change it
12. 12.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
13. 13.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
14. 14.True or false: cutting the lemon is a job a child can do. (a) False (b) True
15. 15.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False
17. 17.🛟 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
18. 18.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) whoever is fastest (d) only an adult
19. 19.True or false: yeast is needed for the secret lemon message. (a) True (b) False
20. 20.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) putting the iron away (d) writing the message
21. 21.🔍 Which is the odd one out? (a) cutting the lemon (b) ironing the paper (c) putting the iron away (d) letting the paper dry
22. 22.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) dry juice is see-through (c) the ink is magnetic (d) the paper ate it
23. 23.True or false: putting the iron away is a job a child can do. (a) False (b) True
24. 24.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) writing the message (d) plugging in the iron
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) the same cotton bud (c) how dark the writing is
26. 26.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
27. 27.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) yeast (c) a cotton bud (d) a mirror
28. 28.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) writing turns green (d) the paper floats
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) the kind of juice (c) how dark the writing is (d) the ironing time
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we measure it (c) we change it
31. 31.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a mirror (c) a cotton bud (d) white paper
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) the ironing time (c) the same paper (d) the kind of juice
33. 33.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) chemical (c) musical (d) magnetic
34. 34.⚖️ 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) True (b) False
35. 35.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) plugging in the iron (c) letting the paper dry (d) cutting the lemon
36. 36.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
37. 37.True or false: ironing the paper is a job for an adult. (a) False (b) True
38. 38.True or false: letting the paper dry is a job a child can do. (a) True (b) False
39. 39.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
40. 40.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it

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