Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 374 · 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.🧺 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) a small bowl (d) a battery cell
2. 2.⚖️ 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 same paper (c) the kind of juice
3. 3.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
4. 4.⚖️ 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 cotton bud
5. 5.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
6. 6.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is magnetic (c) it is sticky (d) it can burn skin
7. 7.🛟 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
8. 8.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) brown (c) white (d) green
9. 9.⚖️ 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 same cotton bud (c) how dark the writing is (d) the ironing time
10. 10.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if shaken (c) yes, in the dark (d) yes, if cooled
11. 11.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) the ink is magnetic (c) it turned into air (d) dry juice is see-through
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) a small bowl (c) an adult with an iron (d) lemon juice
13. 13.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
14. 14.⚖️ 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
15. 15.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a cotton bud (c) turmeric powder (d) lemon juice
16. 16.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) writing the message (c) reading the message (d) putting the iron away
17. 17.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) putting the iron away (d) writing the message
18. 18.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) writing stays faint (c) the paper floats (d) it gets darker
19. 19.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
20. 20.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
21. 21.⚖️ 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
22. 22.True or false: writing the message is a job for an adult. (a) False (b) True
23. 23.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
24. 24.⚖️ 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) False (b) True
25. 25.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) blue words (c) dark brown words (d) almost nothing
26. 26.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) white paper (c) lemon juice (d) an adult with an iron
28. 28.🔍 Which is the odd one out? (a) letting the paper dry (b) plugging in the iron (c) cutting the lemon (d) ironing the paper
29. 29.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
30. 30.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a mirror (c) a battery cell (d) a balloon
31. 31.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
32. 32.True or false: plugging in the iron is a job a child can do. (a) True (b) False
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) lemon juice (c) a magnet (d) a small bowl
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False
35. 35.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) reading the message (d) cutting the lemon
36. 36.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) writing the message (c) plugging in the iron (d) putting the iron away
37. 37.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) an adult with an iron (c) a magnet (d) yeast
38. 38.⚖️ 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 change it (c) we measure it
39. 39.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
40. 40.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True

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