Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 72 · 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.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) putting the iron away (c) writing the message (d) ironing the paper
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) white paper (d) a balloon
3. 3.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) brown (c) white (d) blue
4. 4.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a balloon (c) white paper (d) yeast
5. 5.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) an adult with an iron (c) a mirror (d) a battery cell
6. 6.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
7. 7.🧺 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) a battery cell (d) a small bowl
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we keep it the same (c) we change it
9. 9.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the kind of juice (c) the iron setting
11. 11.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
12. 12.⚖️ 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 same paper (d) how dark the writing is
13. 13.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
14. 14.True or false: white paper is needed for the secret lemon message. (a) True (b) False
15. 15.🔮 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
16. 16.⚖️ 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 kind of juice (c) the same paper (d) the iron setting
17. 17.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a small bowl (c) turmeric powder (d) lemon juice
18. 18.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) letting the paper dry (c) reading the message (d) cutting the lemon
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False
20. 20.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
21. 21.True or false: yeast is needed for the secret lemon message. (a) False (b) True
22. 22.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) wash your hands (c) lick your fingers (d) rub your eyes
23. 23.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) no, it stays brown (d) yes, if shaken
24. 24.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is magnetic (c) it can burn skin (d) it is sticky
25. 25.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
26. 26.True or false: putting the iron away is a job a child can do. (a) False (b) True
27. 27.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
28. 28.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a cotton bud (c) turmeric powder (d) a magnet
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we change it (c) we keep it the same
30. 30.⚖️ 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 measure it (c) we keep it the same
31. 31.🔍 Which is the odd one out? (a) putting the iron away (b) cutting the lemon (c) letting the paper dry (d) ironing the paper
32. 32.🔍 Which is the odd one out? (a) putting the iron away (b) reading the message (c) ironing the paper (d) cutting the lemon
33. 33.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
34. 34.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
35. 35.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the ink is magnetic (c) dry juice is see-through (d) the paper ate it
36. 36.True or false: a battery cell is not needed for the secret lemon message. (a) True (b) False
37. 37.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
38. 38.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
39. 39.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) musical (d) chemical
40. 40.🔍 Which is the odd one out? (a) letting the paper dry (b) ironing the paper (c) reading the message (d) dipping the cotton bud

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