Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 641 · 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.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) a small bowl (d) a balloon
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we measure it (c) we keep it the same
3. 3.🔍 Which is the odd one out? (a) dipping the cotton bud (b) reading the message (c) writing the message (d) plugging in the iron
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) the same paper (c) the iron setting (d) the ironing time
5. 5.🔍 Which is the odd one out? (a) plugging in the iron (b) cutting the lemon (c) ironing the paper (d) writing the message
6. 6.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
7. 7.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) yeast (d) white paper
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) False (b) True
9. 9.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the juice scorches first (c) the iron is brown (d) paper turns lemony
10. 10.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) reading the message (c) plugging in the iron (d) cutting the lemon
11. 11.True or false: cutting the lemon is a job a child can do. (a) True (b) False
12. 12.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
13. 13.⚖️ 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
14. 14.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) lick your fingers (c) skip washing (d) rub your eyes
15. 15.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) plugging in the iron (c) ironing the paper (d) dipping the cotton bud
16. 16.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) yeast (c) lemon juice (d) turmeric powder
17. 17.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) the ink is magnetic (c) dry juice is see-through (d) it turned into air
18. 18.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) turmeric powder (d) an adult with an iron
19. 19.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
20. 20.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it can burn skin (c) it is magnetic (d) it is cold
21. 21.⚖️ 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 ironing time (c) the kind of juice
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) the kind of juice (c) how dark the writing is (d) the same cotton bud
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) True (b) False
24. 24.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we measure it (b) we change it (c) we keep it the same
26. 26.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we keep it the same (c) we change it
28. 28.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) an adult with an iron (c) a battery cell (d) a small bowl
29. 29.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) a battery cell (d) white paper
31. 31.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
32. 32.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
33. 33.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if cooled (c) yes, if shaken (d) no, it stays brown
34. 34.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a magnet (c) a cotton bud (d) an adult with an iron
35. 35.🔮 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
36. 36.⚖️ 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
37. 37.🔮 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
38. 38.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) writing the message (d) cutting the lemon
39. 39.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
40. 40.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) the youngest child (c) any child (d) whoever is fastest

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