Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 71 · 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.⚖️ 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
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) True (b) False
3. 3.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
4. 4.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) chemical (c) magnetic (d) physical
5. 5.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) turmeric powder (c) a cotton bud (d) lemon juice
6. 6.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) no, it stays brown (c) yes, in the dark (d) yes, if cooled
7. 7.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the juice scorches first (c) the iron is brown (d) heat adds colour
8. 8.⚖️ 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 measure it (c) we keep it the same
9. 9.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
10. 10.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) blue (c) brown (d) white
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) False (b) True
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we measure it (c) we keep it the same
13. 13.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) a mirror (d) a small bowl
14. 14.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
15. 15.⚖️ 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
16. 16.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
17. 17.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
18. 18.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is magnetic (c) it can burn skin (d) it is sticky
19. 19.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) only an adult (c) any child (d) the youngest child
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) a small bowl (d) a magnet
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) the ironing time (c) how dark the writing is (d) the same paper
22. 22.🔍 Which is the odd one out? (a) dipping the cotton bud (b) ironing the paper (c) reading the message (d) letting the paper dry
23. 23.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) dipping the cotton bud (d) putting the iron away
24. 24.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
25. 25.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) the same paper (c) how dark the writing is (d) the kind of juice
27. 27.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a cotton bud (c) an adult with an iron (d) a balloon
29. 29.⚖️ 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
30. 30.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
31. 31.True or false: cutting the lemon is a job a child can do. (a) True (b) False
32. 32.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) a battery cell (d) a small bowl
34. 34.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) writing the message (d) ironing the paper
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
36. 36.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
37. 37.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) letting the paper dry (c) writing the message (d) plugging in the iron
38. 38.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
39. 39.🔍 Which is the odd one out? (a) writing the message (b) reading the message (c) cutting the lemon (d) letting the paper dry
40. 40.🔍 Which is the odd one out? (a) cutting the lemon (b) writing the message (c) putting the iron away (d) ironing the paper

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