Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 44 · 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.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) the youngest child (d) only an adult
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we measure it (c) we keep it the same
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a small bowl (c) white paper (d) turmeric powder
4. 4.True or false: cutting the lemon is a job a child can do. (a) False (b) True
5. 5.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) letting the paper dry (d) ironing the paper
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we keep it the same (c) we change it
7. 7.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) writing stays faint (d) the paper floats
8. 8.🔍 Which is the odd one out? (a) reading the message (b) plugging in the iron (c) ironing the paper (d) cutting the lemon
9. 9.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
10. 10.True or false: cutting the lemon is a job for an adult. (a) False (b) True
11. 11.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) it turned into air (c) dry juice is see-through (d) the paper ate it
12. 12.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) cutting the lemon (c) ironing the paper (d) dipping the cotton bud
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) True (b) False
14. 14.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
15. 15.True or false: plugging in the iron is a job a child can do. (a) False (b) True
16. 16.True or false: putting the iron away is a job for an adult. (a) False (b) True
17. 17.True or false: turmeric powder is not needed for the secret lemon message. (a) True (b) False
18. 18.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) almost nothing (d) a rainbow
19. 19.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) no, it stays brown (d) yes, in the dark
20. 20.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
21. 21.⚖️ 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 measure it (c) we keep it the same
22. 22.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) an adult with an iron (c) a battery cell (d) a mirror
23. 23.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a cotton bud (c) turmeric powder (d) an adult with an iron
24. 24.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) paper turns lemony (c) the juice scorches first (d) the iron is brown
25. 25.⚖️ 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
26. 26.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we keep it the same (c) we measure it
28. 28.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
29. 29.True or false: writing the message is a job a child can do. (a) False (b) True
30. 30.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) yeast (c) turmeric powder (d) white paper
31. 31.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) chemical (d) physical
32. 32.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a small bowl (c) lemon juice (d) a battery cell
34. 34.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) wash your hands (c) rub your eyes (d) lick your fingers
35. 35.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it can burn skin (c) it is cold (d) it is magnetic
36. 36.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
37. 37.True or false: ironing the paper is a job a child can do. (a) True (b) False
38. 38.🧺 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 magnet
39. 39.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) blue (d) green
40. 40.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True

Free science experiments lessons, practice and worksheets at talentjr.in/science-experiments-for-kids