Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 307 · 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: letting the paper dry is a job for an adult. (a) False (b) True
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) a small bowl (c) lemon juice (d) a cotton bud
3. 3.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) dry juice is see-through (c) it turned into air (d) the ink is magnetic
4. 4.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) physical (c) magnetic (d) musical
5. 5.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
6. 6.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
7. 7.🍋 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
8. 8.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) the paper floats (c) writing stays faint (d) writing turns green
9. 9.True or false: writing the message is a job a child can do. (a) False (b) True
10. 10.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) writing the message (c) dipping the cotton bud (d) plugging in the iron
11. 11.🔍 Which is the odd one out? (a) ironing the paper (b) reading the message (c) letting the paper dry (d) writing the message
12. 12.⚖️ 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
13. 13.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) a magnet (d) a cotton bud
14. 14.True or false: ironing the paper is a job a child can do. (a) True (b) False
15. 15.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) lemon juice (c) turmeric powder (d) a cotton bud
16. 16.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
17. 17.True or false: a balloon 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? What do we do with “how dark the writing is”? (a) we keep it the same (b) we change it (c) we measure it
19. 19.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
20. 20.⚖️ 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 measure it (c) we keep it the same
21. 21.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
22. 22.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) writing the message (c) ironing the paper (d) putting the iron away
23. 23.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) blue (c) brown (d) white
24. 24.🔍 Which is the odd one out? (a) reading the message (b) putting the iron away (c) plugging in the iron (d) ironing the paper
25. 25.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) turmeric powder (c) a magnet (d) yeast
26. 26.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
27. 27.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
28. 28.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) dipping the cotton bud (c) ironing the paper (d) putting the iron away
29. 29.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it can burn skin (d) it is cold
30. 30.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) lemon juice (c) a battery cell (d) an adult with an iron
31. 31.🔮 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
32. 32.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
33. 33.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
34. 34.🔍 Which is the odd one out? (a) putting the iron away (b) letting the paper dry (c) plugging in the iron (d) ironing the paper
35. 35.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) an adult with an iron (c) lemon juice (d) white paper
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we change it (c) we keep it the same
37. 37.True or false: putting the iron away is a job a child can do. (a) True (b) False
38. 38.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
39. 39.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) the youngest child (c) only an adult (d) any child
40. 40.🔍 Which is the odd one out? (a) ironing the paper (b) putting the iron away (c) cutting the lemon (d) writing the message

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