Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 545 · 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 keep it the same (b) we measure it (c) we change it
2. 2.🍋 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
3. 3.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) False (b) True
5. 5.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
6. 6.True or false: plugging in the iron is a job a child can do. (a) True (b) False
7. 7.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
8. 8.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a battery cell (c) an adult with an iron (d) a magnet
9. 9.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) white paper (c) a small bowl (d) a magnet
10. 10.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a battery cell (c) a magnet (d) a cotton bud
11. 11.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
12. 12.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) cutting the lemon (c) dipping the cotton bud (d) writing the message
13. 13.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
14. 14.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
15. 15.True or false: white paper is needed for the secret lemon message. (a) False (b) True
16. 16.🔍 Which is the odd one out? (a) letting the paper dry (b) ironing the paper (c) plugging in the iron (d) putting the iron away
17. 17.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) False (b) True
19. 19.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) skip washing (c) lick your fingers (d) wash your hands
20. 20.⚖️ 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) how dark the writing is (c) the kind of juice (d) the iron setting
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False
22. 22.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
23. 23.🧺 Which of these is not needed for the secret lemon message? (a) a balloon (b) an adult with an iron (c) a small bowl (d) lemon juice
24. 24.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
25. 25.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, if shaken (c) yes, in the dark (d) no, it stays brown
26. 26.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) an adult with an iron (d) a battery cell
28. 28.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) yeast (c) turmeric powder (d) a small bowl
29. 29.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) only an adult (d) the youngest child
30. 30.🔍 Which is the odd one out? (a) reading the message (b) letting the paper dry (c) writing the message (d) putting the iron away
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we measure it (c) we keep it the same
32. 32.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) cutting the lemon (d) writing the message
33. 33.⚖️ 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
34. 34.True or false: plugging in the iron is a job for an adult. (a) True (b) False
35. 35.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
36. 36.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) cutting the lemon (c) ironing the paper (d) dipping the cotton bud
37. 37.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) writing stays faint (d) the paper floats
38. 38.True or false: white paper 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 same cotton bud is the one thing we change. (a) True (b) False
40. 40.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it

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