Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 728 · 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.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
2. 2.🔍 Which is the odd one out? (a) dipping the cotton bud (b) cutting the lemon (c) plugging in the iron (d) ironing the paper
3. 3.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
4. 4.🧺 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) yeast
5. 5.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) it gets darker (d) writing stays faint
6. 6.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) white (c) brown (d) green
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the iron setting (b) the same cotton bud (c) the kind of juice (d) the ironing time
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) True (b) False
9. 9.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) paper turns lemony (c) the iron is brown (d) the juice scorches first
10. 10.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) an adult with an iron (c) a balloon (d) white paper
11. 11.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) cutting the lemon (d) reading the message
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) a mirror (d) an adult with an iron
13. 13.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
14. 14.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) cutting the lemon (c) dipping the cotton bud (d) putting the iron away
15. 15.🔍 Which is the odd one out? (a) dipping the cotton bud (b) putting the iron away (c) writing the message (d) reading the message
16. 16.🍋 Which of these steps is a job a child can do? (a) writing the message (b) plugging in the iron (c) putting the iron away (d) ironing the paper
17. 17.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) chemical (d) magnetic
18. 18.⚖️ 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 ironing time (c) how dark the writing is
19. 19.⚖️ 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 keep it the same (c) we change it
20. 20.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a cotton bud (c) a battery cell (d) an adult with an iron
21. 21.🔍 Which is the odd one out? (a) putting the iron away (b) letting the paper dry (c) cutting the lemon (d) ironing the paper
22. 22.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) only an adult (c) the youngest child (d) any child
23. 23.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
24. 24.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
25. 25.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
26. 26.⚖️ 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
27. 27.⚖️ 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
28. 28.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if cooled (c) yes, if shaken (d) yes, in the dark
29. 29.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
30. 30.True or false: putting the iron away is a job for an adult. (a) True (b) False
31. 31.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) writing the message (d) ironing the paper
32. 32.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a small bowl (c) a mirror (d) an adult with an iron
34. 34.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
35. 35.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a small bowl (c) a battery cell (d) an adult with an iron
36. 36.🛟 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
37. 37.True or false: letting the paper dry is a job a child can do. (a) False (b) True
38. 38.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is sticky (c) it can burn skin (d) it is magnetic
39. 39.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) reading the message (d) plugging in the iron
40. 40.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed

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