Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 632 · 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.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
2. 2.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) only an adult (d) whoever is fastest
3. 3.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) ironing the paper (c) putting the iron away (d) cutting the lemon
4. 4.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) reading the message (d) ironing the paper
5. 5.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
6. 6.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
7. 7.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) the ink is magnetic (d) dry juice is see-through
8. 8.⚖️ 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 ironing time (c) how dark the writing is (d) the same cotton bud
9. 9.🔍 Which is the odd one out? (a) plugging in the iron (b) writing the message (c) ironing the paper (d) putting the iron away
10. 10.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) blue (c) brown (d) white
11. 11.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) turmeric powder (c) white paper (d) yeast
12. 12.True or false: a balloon is not 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 same cotton bud is what we measure. (a) False (b) True
14. 14.True or false: yeast is needed for the secret lemon message. (a) True (b) False
15. 15.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
16. 16.🧺 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 mirror
17. 17.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
18. 18.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) it gets darker (c) writing stays faint (d) writing turns green
19. 19.⚖️ 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
20. 20.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) cutting the lemon (d) putting the iron away
21. 21.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
22. 22.🛟 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
23. 23.⚖️ 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) True (b) False
24. 24.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
25. 25.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) the juice scorches first (d) heat adds colour
26. 26.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) dark brown words (c) blue words (d) a rainbow
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a cotton bud (c) white paper (d) a battery cell
28. 28.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
29. 29.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) white paper (c) a cotton bud (d) a battery cell
30. 30.⚖️ 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 keep it the same (c) we measure it
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) a magnet (d) an adult with an iron
32. 32.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
33. 33.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
34. 34.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, in the dark (c) no, it stays brown (d) yes, if cooled
35. 35.True or false: a battery cell is not needed for the secret lemon message. (a) True (b) False
36. 36.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) how dark the writing is (c) the same cotton bud (d) the kind of juice
38. 38.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
39. 39.🛟 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
40. 40.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) white paper (c) yeast (d) lemon juice

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