Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 759 · 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.⚖️ 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
2. 2.⚖️ 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 same cotton bud (d) the same paper
3. 3.True or false: letting the paper dry is a job a child can do. (a) True (b) False
4. 4.⚖️ 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
5. 5.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
6. 6.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) the juice scorches first (d) paper turns lemony
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
8. 8.🔍 Which is the odd one out? (a) putting the iron away (b) letting the paper dry (c) ironing the paper (d) cutting the lemon
9. 9.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) writing the message (c) putting the iron away (d) dipping the cotton bud
10. 10.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) physical (c) musical (d) magnetic
11. 11.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
12. 12.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) wash your hands (c) skip washing (d) lick your fingers
13. 13.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) dry juice is see-through (c) it turned into air (d) the ink is magnetic
14. 14.True or false: a battery cell is not needed for the secret lemon message. (a) True (b) False
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same cotton bud (b) the same paper (c) the ironing time (d) how dark the writing is
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a mirror (c) lemon juice (d) an adult with an iron
17. 17.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) white paper (c) a cotton bud (d) an adult with an iron
18. 18.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) a battery cell (c) yeast (d) turmeric powder
19. 19.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) reading the message (c) dipping the cotton bud (d) writing the message
20. 20.True or false: writing the message is a job a child can do. (a) True (b) False
21. 21.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
22. 22.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, in the dark (c) yes, if cooled (d) no, it stays brown
23. 23.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) lemon juice (c) an adult with an iron (d) white paper
24. 24.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) whoever is fastest (d) only an adult
25. 25.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
26. 26.True or false: cutting the lemon is a job for an adult. (a) True (b) False
27. 27.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
28. 28.⚖️ 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
29. 29.⚖️ 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
30. 30.🔍 Which is the odd one out? (a) ironing the paper (b) putting the iron away (c) cutting the lemon (d) writing the message
31. 31.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a magnet (c) a mirror (d) turmeric powder
32. 32.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) lemon juice (c) an adult with an iron (d) a balloon
34. 34.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
35. 35.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
36. 36.🛟 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
37. 37.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
38. 38.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
39. 39.True or false: plugging in the iron is a job a child can do. (a) False (b) True
40. 40.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) blue (d) green

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