Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 489 · 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 of these is not needed for the secret lemon message? (a) a magnet (b) lemon juice (c) a cotton bud (d) white paper
2. 2.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
3. 3.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) white (d) blue
4. 4.True or false: ironing the paper is a job for an adult. (a) False (b) True
5. 5.🧺 Do we need a small bowl 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) a magnet (b) a cotton bud (c) white paper (d) lemon juice
7. 7.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) how dark the writing is (c) the same paper (d) the iron setting
9. 9.⚖️ 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
10. 10.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) plugging in the iron (c) reading the message (d) writing the message
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) a mirror (d) lemon juice
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a battery cell (c) a cotton bud (d) a small bowl
13. 13.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
15. 15.⚖️ 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
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) an adult with an iron (d) turmeric powder
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) how dark the writing is (c) the same cotton bud (d) the kind of juice
18. 18.🔍 Which is the odd one out? (a) ironing the paper (b) dipping the cotton bud (c) plugging in the iron (d) cutting the lemon
19. 19.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
20. 20.⚖️ 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
21. 21.🛟 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
22. 22.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
23. 23.⚖️ 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 kind of juice (c) the ironing time
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) True (b) False
25. 25.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
26. 26.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) physical (c) musical (d) magnetic
27. 27.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) putting the iron away (d) dipping the cotton bud
28. 28.True or false: white paper is needed for the secret lemon message. (a) False (b) True
29. 29.🔮 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
30. 30.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
31. 31.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
32. 32.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) lemon juice (c) yeast (d) a cotton bud
33. 33.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) a rainbow (c) almost nothing (d) dark brown words
34. 34.⚖️ 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
35. 35.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) reading the message (d) ironing the paper
36. 36.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) wash your hands (c) lick your fingers (d) skip washing
37. 37.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
38. 38.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is magnetic (c) it is sticky (d) it can burn skin
39. 39.True or false: ironing the paper is a job a child can do. (a) True (b) False
40. 40.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed

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