Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 339 · 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, if shaken (b) no, it stays brown (c) yes, in the dark (d) yes, if cooled
2. 2.⚖️ 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
3. 3.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing stays faint (c) it gets darker (d) writing turns green
4. 4.⚖️ 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 keep it the same (c) we change it
5. 5.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
6. 6.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a small bowl (c) a mirror (d) lemon juice
8. 8.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a battery cell (c) yeast (d) a small bowl
9. 9.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a balloon (c) lemon juice (d) a magnet
10. 10.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) a rainbow (d) almost nothing
11. 11.🔍 Which is the odd one out? (a) writing the message (b) reading the message (c) letting the paper dry (d) putting the iron away
12. 12.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
13. 13.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) an adult with an iron (c) lemon juice (d) white paper
15. 15.True or false: yeast is needed for the secret lemon message. (a) True (b) False
16. 16.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
17. 17.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) letting the paper dry (c) cutting the lemon (d) putting the iron away
18. 18.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) an adult with an iron (c) lemon juice (d) turmeric powder
19. 19.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) lick your fingers (c) rub your eyes (d) skip washing
20. 20.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) reading the message (d) ironing the paper
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) False (b) True
22. 22.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
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 cotton bud (b) the ironing time (c) how dark the writing is (d) the kind of juice
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we measure it (c) we keep it the same
25. 25.⚖️ 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 same cotton bud (c) the kind of juice
26. 26.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
27. 27.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) magnetic (c) musical (d) physical
28. 28.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) only an adult (d) whoever is fastest
29. 29.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) reading the message (c) writing the message (d) dipping the cotton bud
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False
31. 31.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the iron is brown (c) the juice scorches first (d) paper turns lemony
32. 32.🔍 Which is the odd one out? (a) ironing the paper (b) plugging in the iron (c) cutting the lemon (d) letting the paper dry
33. 33.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) how dark the writing is (c) the ironing time (d) the kind of juice
35. 35.⚖️ 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 same paper
36. 36.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
37. 37.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
38. 38.🧺 Which of these is not needed for the secret lemon message? (a) yeast (b) white paper (c) a cotton bud (d) lemon juice
39. 39.True or false: ironing the paper is a job a child can do. (a) True (b) False
40. 40.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True

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