1. Science Grade 8 Unit 7 Test 2018-2019 (8.5DE)

2. 1 Which of these formulas contain equal numbers of nitrogen atoms?
Formulas I and III
Formulas I and IV
Formulas II and III
Formulas I, II, and V
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3. 2 CH4 is an example of a —
F chemical equation G chemical formula H chemical reaction J chemical symbol

4. One of the original compounds came out of solution.
3 During an investigation, a student combined the two clear, colorless solutions shown below.
The student observed that the temperature changed from 25°C to 23°C when the solutions were combined and that a white substance rapidly formed and settled to the bottom of the container. What most likely happened to produce these results?
One of the original compounds came out of solution.
The solutions reacted chemically.
Some of the water froze into ice crystals.
Rapid evaporation of water occurred, leaving a solid.
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5. How many atoms are represented in the reactants of this equation?
4 The equation below represents a chemical reaction that occurs in living cells.
How many atoms are represented in the reactants of this equation? 6 12 24
J 36
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6. A dark solid formed on the zinc metal.
5 For an investigation a student poured a blue solution of CuSO4 into a beaker. The student placed a shiny, silver-colored strip of zinc metal in the solution and observed the changes.
The student inferred that a chemical reaction occurred. What evidence supports this inference?
A dark solid formed on the zinc metal.
The zinc metal remained silver-colored and shiny.
The CuSO4 solution turned blue when the zinc metal was added.
None of these
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7. 6. The formula for glucose is C6H12O6
6 The formula for glucose is C6H12O6 . How many elements does glucose contain? 1 3 24
J 432
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8. 7. H2 + O2 ------> H2O2 16g + 2g ------>18g
The chemical equation above demonstrates that –
matter cannot be created or destroyed by a chemical reaction
the reactants are the same substances as the products
the number of molecules in the reactants is equal to the number of molecules in the products
the atoms on the reactants side are changed into different atoms on the products side

9. 8. Serotonin is a chemical substance that acts as a neurotransmitter
8 Serotonin is a chemical substance that acts as a neurotransmitter. It helps relay messages in the human brain. The formula for one molecule of serotonin is shown below.
C10H12N2O
How many atoms in all are in a molecule of serotonin?
Record your answer and fill in the bubbles on your answer document. Be sure to use the correct place value.
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10. 9 Some students in a chemistry lab conducted an investigation in which they added four different solid substances to separate beakers of water. They stirred the mixtures for one minute and then recorded their observations in the table below.
Which substance most likely caused a new substance to be formed when mixed with water?
Substance 1
Substance 2
Substance 3
Substance 4
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11. 10 Which of the following equations demonstrates an actual chemical reaction that forms a new substance?
2N + 2HCl → N2Cl2 + H2
H2O + NaCl → H2O
Zn + Al + Cu → Zn + Cu + Al
J C12H22O11 + H2O → H2O + C12H22O11
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BE SURE YOU HAVE RECORDED ALL OF YOUR ANSWERS ON YOUR ANSWER DOCUMENT
STOP

12. Which of the following represents a single atom?Mn O2
K2O 2K

13. 12. Coal contains carbon and other elements. Carbon dioxide
forms when coal burns in the presence of oxygen. Which of these
is the best evidence that a chemical reaction occurs when coal burns?
F. The shape of the coal changes
G. Oxygen is present
H. A new substance is produced
J. Coal is made up of more than one element