Question

practice: classification
part 1: classify the following as a substance (s) or a mixture (m).
__1. table salt (nacl) 2. trail mix __3. sugar
__4. copper 5. cereal __6. concrete
part 2: classify the following substances as elements (e) or compounds (c).
__7. mercury 8. water __9. carbon dioxide
__10. iron 11. aluminum __12. oxygen (o₂)
part 3: classify the following mixtures as homogeneous (ho) or heterogeneous (he).
__13. coffee 14. pizza __15. sand
__16. saltwater 17. bronze __18. milk
__19. paint 20. air __21. soil
part 4: classify the following as an element (e), compound (c), homogeneous mixture (ho) or heterogeneous mixture (he).
__22. calcium 23. hydrogen (h₂) __24. orange juice with pulp
__25. baking soda (nahco₃) 26. helium __27. limestone (caco₃)
__28. salad dressing __29. vinegar (ch₃cooh)
part 5: each of the following circles represents an atom. if two atoms are touching than they are bonded together. knowing this, classify each picture as one of the following:
a = element
b = compound
c = mixture of elements
d = mixture of compounds
e = mixture of elements and compounds

Explanation:

Step1: Recall definitions

A substance has a fixed - composition, while a mixture has a variable composition. An element is a pure substance made of only one type of atom, and a compound is a pure substance made of two or more different types of atoms chemically bonded. A homogeneous mixture has a uniform composition throughout, and a heterogeneous mixture has a non - uniform composition.

Step2: Classify Part 1

1. Table salt (NaCl) is a substance (S) as it has a fixed chemical formula.
2. Trail mix is a mixture (M) as it contains different components like nuts, raisins etc.
3. Sugar is a substance (S) as it is a pure compound.
4. Copper is a substance (S) as it is an element.
5. Cereal is a mixture (M) as it contains different grains, flakes etc.
6. Concrete is a mixture (M) as it is made of cement, sand, gravel etc.

Step3: Classify Part 2

1. Mercury is an element (E) as it is made of only mercury atoms.
2. Water is a compound (C) as it is made of hydrogen and oxygen atoms chemically bonded ($H_2O$).
3. Carbon dioxide is a compound (C) as it is made of carbon and oxygen atoms chemically bonded ($CO_2$).
4. Iron is an element (E) as it is made of only iron atoms.
5. Aluminum is an element (E) as it is made of only aluminum atoms.
6. Oxygen ($O_2$) is an element (E) as it is made of only oxygen atoms.

Step4: Classify Part 3

1. Coffee is a homogeneous mixture (HO) as it has a uniform composition when well - mixed.
2. Pizza is a heterogeneous mixture (HE) as it has different components like cheese, sauce, toppings etc. with non - uniform distribution.
3. Sand is a heterogeneous mixture (HE) as it contains different sized particles and may have different minerals.
4. Saltwater is a homogeneous mixture (HO) as the salt is uniformly dissolved in water.
5. Bronze is a homogeneous mixture (HO) as it is an alloy with a relatively uniform composition.
6. Milk is a homogeneous mixture (HO) when well - mixed (although it is a colloid).
7. Paint is a homogeneous mixture (HO) as it has a uniform composition.
8. Air is a homogeneous mixture (HO) as it has a relatively uniform composition of nitrogen, oxygen etc.
9. Soil is a heterogeneous mixture (HE) as it contains different components like minerals, organic matter etc. non - uniformly.

Step5: Classify Part 4

1. Calcium is an element (E).
2. Hydrogen ($H_2$) is an element (E).
3. Orange juice with pulp is a heterogeneous mixture (HE) due to the presence of pulp.
4. Baking soda ($NaHCO_3$) is a compound (C).
5. Helium is an element (E).
6. Limestone ($CaCO_3$) is a compound (C).
7. Salad dressing is a heterogeneous mixture (HE) as it may separate into layers.
8. Vinegar ($CH_3COOH$) is a compound (C).

Step6: Classify Part 5

1. Mixture of compounds (D) as there are different types of compounds present.
2. Compound (B) as all the molecules are the same type of compound.
3. Element (A) as all the atoms are of the same type.
4. Element (A) as all the molecules are made of the same type of atom.
5. Compound (B) as all the molecules are the same type of compound.
6. Mixture of elements and compounds (E) as there are both single - atom elements and compounds present.

Answer:

1. S
2. M
3. S
4. S
5. M
6. M
7. E
8. C
9. C
10. E
11. E
12. E
13. HO
14. HE
15. HE
16. HO
17. HO
18. HO
19. HO
20. HO
21. HE
22. E
23. E
24. HE
25. C
26. E
27. C
28. HE
29. C
30. D
31. B
32. A
33. A
34. B
35. E