Elements, Compounds & Mixtures- Day 1 2013 | PDF - Free Printable

Let’s go through each question step by step.

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Question 1:

We have three boxes with different particle diagrams.

- Box A (left): Contains only black dots, all separate. These are individual atoms of the same type → so this is *atoms of an element*.

- Box B (middle): Contains pairs of white circles stuck together. Each pair is identical → molecules made of one kind of atom → *molecules of an element* (like O₂ or N₂).

- Box C (right): Contains groups of two different colored circles stuck together (one black, one white). All groups are the same → molecules made of two different types of atoms → *molecules of a compound*.

Now answer each part:

a) Molecules of an element? → Box B
b) Molecules of a compound? → Box C
c) Atoms of an element? → Box A
d) Do any contain a mixture? → No. A mixture would have different kinds of particles not chemically bonded — like some single atoms and some molecules mixed together. All boxes show only one type of particle each → no mixtures.

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Question 2:

Circle elements, underline compounds.

Elements = made of only one type of atom.
Compounds = made of two or more different types of atoms chemically bonded.

a) Li → element → circle
b) N₂ → element (only nitrogen) → circle
c) CO → carbon + oxygen → compound → underline
d) Cl₂ → element → circle
e) S₈ → sulfur only → element → circle
f) NaCl → sodium + chlorine → compound → underline

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Question 3:

How many elements make up each compound?

Count how many *different* element symbols are in each formula.

a) HCl → H and Cl → 2 elements
b) CaCO₃ → Ca, C, O → 3 elements
c) HNO₃ → H, N, O → 3 elements
d) H₂SO₄ → H, S, O → 3 elements
e) CH₃OH → C, H, O → 3 elements

Note: Even though H appears multiple times, it’s still just one element.

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Question 4:

How many atoms in each molecule?

Add up all the subscripts (if no subscript, it’s 1).

a) N₂ → 2 atoms
b) CO₂ → C=1, O=2 → total 3 atoms
c) O₃ → 3 atoms
d) CH₄ → C=1, H=4 → total 5 atoms
e) SO₂ → S=1, O=2 → total 3 atoms
f) C₂H₄ → C=2, H=4 → total 6 atoms

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Question 5:

Circle the molecule with the most atoms in each pair.

a) HCl → 2 atoms; POCl → P=1, O=1, Cl=1 → 3 atoms → circle POCl
b) NH₃ → N=1, H=3 → 4 atoms; HNO₃ → H=1, N=1, O=3 → 5 atoms → circle HNO₃
c) C₃H₈ → C=3, H=8 → 11 atoms; C₂H₅OH → C=2, H=6 (5+1), O=1 → 9 atoms → circle C₃H₈
d) CH₃COCH₃ → Let’s count: C=3 (first CH₃, then CO, then CH₃), H=6 (3+3), O=1 → total 10 atoms; C₆H₆ → C=6, H=6 → 12 atoms → circle C₆H₆

Wait — let me double-check d):

CH₃COCH₃ is acetone:
- First CH₃: 1C, 3H
- CO: 1C, 1O
- Last CH₃: 1C, 3H
Total: C=3, H=6, O=1 → 10 atoms

C₆H₆: benzene → 6C + 6H = 12 atoms → yes, C₆H₆ has more.

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Question 6:

Write the chemical formula for each molecule shown.

First diagram: Two O atoms → O₂
Second: One C, two O → CO₂
Third: Two H, one O → H₂O
Fourth: One N, three H → NH₃

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Final Answers:

→ Question 1:
a) Box B
b) Box C
c) Box A
d) No, none contain a mixture because each box has only one type of particle.

→ Question 2:
Circle: a) Li, b) N₂, d) Cl₂, e) S₈
Underline: c) CO, f) NaCl

→ Question 3:
a) 2, b) 3, c) 3, d) 3, e) 3

→ Question 4:
a) 2, b) 3, c) 3, d) 5, e) 3, f) 6

→ Question 5:
a) POCl, b) HNO₃, c) C₃H₈, d) C₆H₆

→ Question 6:
O₂, CO₂, H₂O, NH₃

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Final Answer:
1. a) Box B, b) Box C, c) Box A, d) No mixture — each box has only one type of particle.
2. Circle: Li, N₂, Cl₂, S₈; Underline: CO, NaCl
3. a) 2, b) 3, c) 3, d) 3, e) 3
4. a) 2, b) 3, c) 3, d) 5, e) 3, f) 6
5. a) POCl, b) HNO₃, c) C₃H₈, d) C₆H₆
6. O₂, CO₂, H₂O, NH₃