Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 454 · 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.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if cooled (c) no, it stays brown (d) yes, if shaken
2. 2.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
3. 3.🍋 Which of these steps is a job for an adult? (a) reading the message (b) letting the paper dry (c) dipping the cotton bud (d) ironing the paper
4. 4.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
5. 5.True or false: reading the message is a job for an adult. (a) True (b) False
6. 6.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
7. 7.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) chemical (c) magnetic (d) physical
8. 8.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) ironing the paper (d) cutting the lemon
9. 9.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a balloon (c) a mirror (d) a small bowl
10. 10.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a mirror (c) a small bowl (d) lemon juice
11. 11.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
12. 12.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a cotton bud (c) turmeric powder (d) white paper
13. 13.True or false: writing the message is a job a child can do. (a) True (b) False
14. 14.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) dry juice is see-through (c) the ink is magnetic (d) the paper ate it
15. 15.🔍 Which is the odd one out? (a) putting the iron away (b) dipping the cotton bud (c) writing the message (d) letting the paper dry
16. 16.🔍 Which is the odd one out? (a) putting the iron away (b) ironing the paper (c) letting the paper dry (d) plugging in the iron
17. 17.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) True (b) False
19. 19.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
20. 20.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) the paper floats (c) writing stays faint (d) writing turns green
21. 21.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
22. 22.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) reading the message (c) ironing the paper (d) putting the iron away
23. 23.True or false: ironing the paper is a job for an adult. (a) True (b) False
24. 24.⚖️ 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
25. 25.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) wash your hands (c) rub your eyes (d) skip washing
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) the same paper (c) the same cotton bud (d) how dark the writing is
27. 27.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) True (b) False
29. 29.🍋 Which of these steps is a job a child can do? (a) writing the message (b) cutting the lemon (c) ironing the paper (d) putting the iron away
30. 30.🧺 Which of these is needed for the secret lemon message? (a) white paper (b) a magnet (c) turmeric powder (d) a battery cell
31. 31.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) blue (d) brown
32. 32.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
33. 33.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
34. 34.True or false: yeast is needed for the secret lemon message. (a) True (b) False
35. 35.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) paper turns lemony (c) heat adds colour (d) the juice scorches first
36. 36.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a balloon (c) an adult with an iron (d) a magnet
37. 37.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
38. 38.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) plugging in the iron (d) dipping the cotton bud
39. 39.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a battery cell (c) lemon juice (d) an adult with an iron
40. 40.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it

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