Invisible Ink Experiment Worksheet

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

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