Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 137 · 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? What do we do with “the same cotton bud”? (a) we measure it (b) we change it (c) we keep it the same
2. 2.🧺 Which of these is not needed for the secret lemon message? (a) a mirror (b) lemon juice (c) a cotton bud (d) an adult with an iron
3. 3.True or false: reading the message is a job a child can do. (a) True (b) False
4. 4.True or false: ironing the paper is a job for an adult. (a) False (b) True
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) False (b) True
6. 6.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
7. 7.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) ironing the paper (d) reading the message
8. 8.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) dipping the cotton bud (d) putting the iron away
9. 9.🍋 Which of these steps is a job for an adult? (a) ironing the paper (b) dipping the cotton bud (c) reading the message (d) writing the message
10. 10.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same cotton bud (b) how dark the writing is (c) the kind of juice
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) an adult with an iron (d) a magnet
13. 13.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) whoever is fastest (c) any child (d) only an adult
14. 14.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
15. 15.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a mirror (c) a cotton bud (d) yeast
16. 16.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
17. 17.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
18. 18.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
19. 19.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
20. 20.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a balloon (c) white paper (d) a battery cell
21. 21.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, if shaken (c) no, it stays brown (d) yes, in the dark
22. 22.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) how dark the writing is (c) the iron setting (d) the kind of juice
24. 24.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) chemical (c) magnetic (d) physical
25. 25.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) dry juice is see-through (c) the paper ate it (d) it turned into air
26. 26.True or false: plugging in the iron is a job a child can do. (a) False (b) True
27. 27.⚖️ 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 ironing time (d) the same cotton bud
28. 28.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
29. 29.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) green (c) brown (d) white
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 keep it the same (c) we measure it
31. 31.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
32. 32.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) plugging in the iron (d) dipping the cotton bud
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) False (b) True
34. 34.🔍 Which is the odd one out? (a) writing the message (b) ironing the paper (c) plugging in the iron (d) putting the iron away
35. 35.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) it gets darker (c) writing stays faint (d) the paper floats
36. 36.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) reading the message (c) putting the iron away (d) ironing the paper
37. 37.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
38. 38.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
39. 39.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
40. 40.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed

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