Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 642 · 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 of these is needed for the secret lemon message? (a) a magnet (b) a mirror (c) yeast (d) an adult with an iron
2. 2.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) writing the message (d) plugging in the iron
3. 3.True or false: ironing the paper is a job for an adult. (a) True (b) False
4. 4.🔮 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
5. 5.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) it turned into air (c) the paper ate it (d) dry juice is see-through
6. 6.🛟 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
7. 7.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) ironing the paper (d) writing the message
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) the same paper (c) how dark the writing is
9. 9.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
10. 10.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) chemical (d) musical
11. 11.🔍 Which is the odd one out? (a) ironing the paper (b) reading the message (c) dipping the cotton bud (d) writing the message
12. 12.True or false: reading the message is a job a child can do. (a) False (b) True
13. 13.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
14. 14.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
15. 15.⚖️ 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
16. 16.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
17. 17.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
18. 18.⚖️ 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) True (b) False
19. 19.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) only an adult (c) whoever is fastest (d) the youngest child
20. 20.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
21. 21.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a balloon (c) lemon juice (d) white paper
22. 22.True or false: cutting the lemon is a job for an adult. (a) False (b) True
23. 23.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a cotton bud (c) yeast (d) a magnet
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) the ironing time (c) how dark the writing is (d) the iron setting
25. 25.🔍 Which is the odd one out? (a) reading the message (b) ironing the paper (c) plugging in the iron (d) putting the iron away
26. 26.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) a rainbow (c) dark brown words (d) almost nothing
27. 27.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
28. 28.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
29. 29.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a balloon (c) a mirror (d) lemon juice
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) a small bowl (d) a mirror
31. 31.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
32. 32.⚖️ 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) True (b) False
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) a small bowl (c) an adult with an iron (d) lemon juice
34. 34.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) plugging in the iron (c) writing the message (d) reading the message
35. 35.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) skip washing (d) wash your hands
36. 36.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) green (c) white (d) brown
37. 37.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) white paper (c) turmeric powder (d) an adult with an iron
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) the iron setting (c) how dark the writing is
39. 39.True or false: cutting the lemon is a job a child can do. (a) True (b) False
40. 40.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True

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