Invisible Ink Experiment Worksheet

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

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