Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 348 · 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.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
2. 2.⚖️ 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 measure it (c) we change it
3. 3.⚖️ 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) 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 mirror (c) lemon juice (d) a cotton bud
5. 5.⚖️ 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 iron setting (c) the same paper (d) the kind of juice
6. 6.True or false: reading the message is a job a child can do. (a) False (b) True
7. 7.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) reading the message (d) putting the iron away
8. 8.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) lemon juice (c) a balloon (d) a small bowl
9. 9.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a cotton bud (c) yeast (d) a battery cell
10. 10.🔮 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
11. 11.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
12. 12.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is magnetic (c) it is cold (d) it is sticky
13. 13.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) brown (c) blue (d) white
14. 14.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) the paper floats (c) writing turns green (d) it gets darker
15. 15.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a small bowl (c) yeast (d) lemon juice
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the ironing time (c) the same cotton bud (d) the same paper
18. 18.🔍 Which is the odd one out? (a) plugging in the iron (b) reading the message (c) writing the message (d) dipping the cotton bud
19. 19.⚖️ 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
20. 20.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) paper turns lemony (c) heat adds colour (d) the juice scorches first
21. 21.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
22. 22.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
23. 23.⚖️ 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
24. 24.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
25. 25.🔍 Which is the odd one out? (a) putting the iron away (b) letting the paper dry (c) cutting the lemon (d) ironing the paper
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) False (b) True
27. 27.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
28. 28.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
29. 29.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
30. 30.True or false: cutting the lemon is a job a child can do. (a) False (b) True
31. 31.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) writing the message (d) ironing the paper
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the iron setting (b) the kind of juice (c) how dark the writing is
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) False (b) True
34. 34.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) rub your eyes (c) lick your fingers (d) wash your hands
35. 35.🍋 Which of these steps is a job for an adult? (a) plugging in the iron (b) reading the message (c) letting the paper dry (d) dipping the cotton bud
36. 36.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
37. 37.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) dipping the cotton bud (d) putting the iron away
38. 38.⚖️ 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) False (b) True
39. 39.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) no, it stays brown (c) yes, if shaken (d) yes, if cooled
40. 40.True or false: a magnet is needed for the secret lemon message. (a) False (b) True

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