Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 648 · 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 ironing time”? (a) we change it (b) we keep it the same (c) we measure it
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) a cotton bud (d) yeast
3. 3.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) white paper (c) lemon juice (d) an adult with an iron
5. 5.⚖️ 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
6. 6.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) yeast (c) a magnet (d) lemon juice
7. 7.🔍 Which is the odd one out? (a) writing the message (b) dipping the cotton bud (c) ironing the paper (d) reading the message
8. 8.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
9. 9.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
10. 10.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
11. 11.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) putting the iron away (c) writing the message (d) plugging in the iron
12. 12.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
13. 13.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) heat adds colour (d) the juice scorches first
14. 14.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) chemical (d) magnetic
15. 15.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
16. 16.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) a rainbow (c) blue words (d) almost nothing
17. 17.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
18. 18.True or false: ironing the paper is a job a child can do. (a) False (b) True
19. 19.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
20. 20.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
21. 21.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) the youngest child (d) only an adult
22. 22.🛟 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
23. 23.🔍 Which is the odd one out? (a) cutting the lemon (b) letting the paper dry (c) putting the iron away (d) ironing the paper
24. 24.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
25. 25.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
26. 26.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) a cotton bud (d) a battery cell
27. 27.True or false: yeast is needed for the secret lemon message. (a) False (b) True
28. 28.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is cold (c) it is sticky (d) it can burn skin
29. 29.⚖️ 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
30. 30.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, in the dark (c) yes, if shaken (d) yes, if cooled
31. 31.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
32. 32.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a cotton bud (c) a magnet (d) white paper
33. 33.⚖️ 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 keep it the same (c) we measure it
34. 34.⚖️ 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
35. 35.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
36. 36.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) blue (c) brown (d) green
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we measure it (c) we keep it the same
38. 38.True or false: putting the iron away is a job a child can do. (a) False (b) True
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same cotton bud (b) how dark the writing is (c) the same paper (d) the kind of juice
40. 40.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False

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