Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 540 · 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 is the odd one out? (a) ironing the paper (b) cutting the lemon (c) writing the message (d) putting the iron away
2. 2.⚖️ 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 keep it the same (c) we change it
3. 3.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
4. 4.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) no, it stays brown (c) yes, if cooled (d) yes, in the dark
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) True (b) False
6. 6.🍋 Which of these steps is a job for an adult? (a) writing the message (b) putting the iron away (c) letting the paper dry (d) reading the message
7. 7.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) only an adult (d) whoever is fastest
8. 8.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a magnet (c) white paper (d) an adult with an iron
9. 9.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) white (c) green (d) brown
10. 10.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
11. 11.True or false: writing the message is a job for an adult. (a) True (b) False
12. 12.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) cutting the lemon (d) reading the message
13. 13.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) blue words (c) dark brown words (d) a rainbow
14. 14.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) lick your fingers (c) rub your eyes (d) wash your hands
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) an adult with an iron (b) a magnet (c) lemon juice (d) white paper
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) True (b) False
18. 18.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
19. 19.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
20. 20.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
21. 21.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is cold (c) it is magnetic (d) it is sticky
22. 22.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing turns green (c) writing stays faint (d) it gets darker
23. 23.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) an adult with an iron (c) a magnet (d) a mirror
24. 24.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
25. 25.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
26. 26.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) a balloon (c) a magnet (d) a battery cell
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) a battery cell (d) lemon juice
28. 28.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) chemical (c) physical (d) musical
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the same cotton bud (c) how dark the writing is (d) the kind of juice
30. 30.🔍 Which is the odd one out? (a) plugging in the iron (b) cutting the lemon (c) ironing the paper (d) letting the paper dry
31. 31.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) heat adds colour (c) the juice scorches first (d) the iron is brown
32. 32.⚖️ 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
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) a mirror (d) a small bowl
35. 35.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
36. 36.🍋 Which of these steps is a job a child can do? (a) dipping the cotton bud (b) putting the iron away (c) ironing the paper (d) plugging in the iron
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we change it (c) we keep it the same
38. 38.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
39. 39.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
40. 40.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) a cotton bud (c) a small bowl (d) lemon juice

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