Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 36 · 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.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) physical (c) chemical (d) magnetic
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we measure it (c) we keep it the same
3. 3.🔍 Which is the odd one out? (a) ironing the paper (b) dipping the cotton bud (c) letting the paper dry (d) reading the message
4. 4.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) a battery cell (c) a magnet (d) turmeric powder
5. 5.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) a balloon (d) white paper
6. 6.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) blue (d) white
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we change it (c) we measure it
8. 8.⚖️ 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 iron setting (c) the kind of juice
9. 9.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
10. 10.True or false: reading the message is a job a child can do. (a) True (b) False
11. 11.⚖️ 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
12. 12.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) it turned into air (c) the paper ate it (d) the ink is magnetic
13. 13.🧺 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) turmeric powder (d) white paper
14. 14.True or false: putting the iron away is a job for an adult. (a) True (b) False
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we change it (c) we measure it
16. 16.🔍 Which is the odd one out? (a) letting the paper dry (b) ironing the paper (c) putting the iron away (d) plugging in the iron
17. 17.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
18. 18.True or false: yeast is needed for the secret lemon message. (a) False (b) True
19. 19.🧺 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 magnet (d) lemon juice
20. 20.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
21. 21.True or false: plugging in the iron is a job for an adult. (a) False (b) True
22. 22.True or false: cutting the lemon is a job a child can do. (a) False (b) True
23. 23.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
24. 24.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
25. 25.🔮 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
26. 26.🔍 Which is the odd one out? (a) reading the message (b) cutting the lemon (c) ironing the paper (d) plugging in the iron
27. 27.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) plugging in the iron (d) letting the paper dry
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) False (b) True
29. 29.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) the iron setting (c) the ironing time (d) how dark the writing is
31. 31.True or false: a battery cell is not needed for the secret lemon message. (a) True (b) False
32. 32.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) a mirror (d) a cotton bud
33. 33.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) writing stays faint (d) it gets darker
34. 34.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) writing the message (d) ironing the paper
35. 35.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) rub your eyes (c) wash your hands (d) skip washing
36. 36.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a mirror (c) a battery cell (d) a small bowl
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we measure it (c) we keep it the same
38. 38.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) cutting the lemon (c) ironing the paper (d) putting the iron away
39. 39.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
40. 40.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed

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