Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 615 · 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.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) white paper (c) a cotton bud (d) a balloon
2. 2.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
3. 3.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
4. 4.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) green (c) brown (d) white
5. 5.🍋 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
6. 6.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) whoever is fastest (c) the youngest child (d) any child
7. 7.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) it gets darker (c) the paper floats (d) writing stays faint
8. 8.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we measure it (c) we change it
10. 10.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) turmeric powder (c) a cotton bud (d) a balloon
11. 11.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
12. 12.⚖️ 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 keep it the same (c) we measure it
13. 13.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
14. 14.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
15. 15.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) yeast (d) a cotton bud
16. 16.⚖️ 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 change it (c) we measure it
17. 17.⚖️ 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 ironing time
18. 18.⚖️ 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 kind of juice (c) the ironing time (d) the same cotton bud
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) True (b) False
20. 20.🔍 Which is the odd one out? (a) letting the paper dry (b) plugging in the iron (c) ironing the paper (d) putting the iron away
21. 21.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) ironing the paper (d) reading the message
22. 22.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a balloon (c) lemon juice (d) turmeric powder
23. 23.True or false: plugging in the iron is a job for an adult. (a) False (b) True
24. 24.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) an adult with an iron (c) lemon juice (d) a mirror
26. 26.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) cutting the lemon (d) dipping the cotton bud
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a cotton bud (c) lemon juice (d) white paper
29. 29.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is cold (c) it can burn skin (d) it is magnetic
30. 30.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a small bowl (c) a magnet (d) a mirror
31. 31.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) ironing the paper (c) reading the message (d) writing the message
32. 32.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a small bowl (c) white paper (d) turmeric powder
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True
34. 34.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) letting the paper dry (d) plugging in the iron
35. 35.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) almost nothing (c) blue words (d) a rainbow
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False
37. 37.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if cooled (c) yes, if shaken (d) no, it stays brown
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we measure it (c) we keep it the same
39. 39.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
40. 40.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False

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