Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 121 · 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.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
2. 2.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
3. 3.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a battery cell (c) lemon juice (d) a magnet
4. 4.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) ironing the paper (c) dipping the cotton bud (d) cutting the lemon
5. 5.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) putting the iron away (d) dipping the cotton bud
6. 6.⚖️ 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 kind of juice (c) the ironing time (d) the iron setting
7. 7.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
8. 8.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a balloon (c) an adult with an iron (d) a battery cell
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we measure it (c) we keep it the same
10. 10.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a cotton bud (c) a balloon (d) a magnet
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we keep it the same (c) we measure it
12. 12.🔍 Which is the odd one out? (a) writing the message (b) reading the message (c) putting the iron away (d) dipping the cotton bud
13. 13.True or false: reading the message is a job for an adult. (a) True (b) False
14. 14.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
15. 15.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) brown (c) blue (d) white
16. 16.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) dry juice is see-through (c) the ink is magnetic (d) it turned into air
17. 17.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it is cold (d) it can burn skin
18. 18.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) rub your eyes (c) skip washing (d) wash your hands
19. 19.⚖️ 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
20. 20.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) dipping the cotton bud (d) ironing the paper
21. 21.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) physical (c) musical (d) chemical
22. 22.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
23. 23.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
24. 24.True or false: cutting the lemon is a job for an adult. (a) False (b) True
25. 25.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) only an adult (d) whoever is fastest
26. 26.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
27. 27.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
28. 28.⚖️ 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 paper (c) the kind of juice (d) the iron setting
29. 29.🔮 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
30. 30.🍋 Which of these steps is a job for an adult? (a) writing the message (b) plugging in the iron (c) letting the paper dry (d) reading the message
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) False (b) True
32. 32.🔮 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
33. 33.⚖️ 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
34. 34.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a small bowl (c) lemon juice (d) a battery cell
35. 35.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
36. 36.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
37. 37.⚖️ 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
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) True (b) False
39. 39.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
40. 40.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a balloon (c) lemon juice (d) a cotton bud

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