Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 628 · 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 is the odd one out? (a) reading the message (b) cutting the lemon (c) dipping the cotton bud (d) letting the paper dry
2. 2.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
3. 3.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
4. 4.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) skip washing (c) rub your eyes (d) lick your fingers
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we measure it (b) we change it (c) we keep it the same
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the iron setting (b) how dark the writing is (c) the kind of juice
7. 7.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
8. 8.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) letting the paper dry (d) putting the iron away
9. 9.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) almost nothing (c) dark brown words (d) a rainbow
10. 10.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
11. 11.True or false: ironing the paper is a job for an adult. (a) True (b) False
12. 12.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
13. 13.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) lemon juice (d) a balloon
14. 14.🔍 Which is the odd one out? (a) putting the iron away (b) cutting the lemon (c) plugging in the iron (d) dipping the cotton bud
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we measure it (c) we change it
16. 16.🔍 Which is the odd one out? (a) plugging in the iron (b) reading the message (c) dipping the cotton bud (d) writing the message
17. 17.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if shaken (c) yes, if cooled (d) yes, in the dark
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) the kind of juice (c) how dark the writing is
19. 19.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) it turned into air (c) dry juice is see-through (d) the ink is magnetic
20. 20.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
21. 21.🔍 Which is the odd one out? (a) writing the message (b) putting the iron away (c) cutting the lemon (d) ironing the paper
22. 22.True or false: writing the message is a job for an adult. (a) True (b) False
23. 23.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
24. 24.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
25. 25.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is cold (c) it can burn skin (d) it is magnetic
26. 26.True or false: cutting the lemon is a job a child can do. (a) False (b) True
27. 27.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) writing the message (d) putting the iron away
28. 28.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) the youngest child (d) only an adult
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) how dark the writing is (b) the iron setting (c) the same cotton bud (d) the kind of juice
30. 30.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
31. 31.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) an adult with an iron (d) a battery cell
32. 32.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) white paper (c) an adult with an iron (d) a mirror
33. 33.True or false: turmeric powder is not needed for the secret lemon message. (a) True (b) False
34. 34.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) writing turns green (c) the paper floats (d) it gets darker
35. 35.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) paper turns lemony (d) the juice scorches first
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False
37. 37.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
38. 38.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) True (b) False
40. 40.True or false: writing the message is a job a child can do. (a) False (b) True

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