Question 1

The chemical equation shown below represents a reaction that produces fuel for certain cars. 
$CO$ + $H_{2}O$→ $CO_{2}$ +$H_{2}$
Which substance represented in this equation is classified as an element?

Accepted Answer

$H_{2}$

Answer

$CO_{2}$

Answer

$H_{2}O$

Answer

$CO$

Question 2

In the chemical reaction shown above, the products are best classified as —

Accepted Answer

two compounds

Answer

two compounds and one element

Answer

two elements

Answer

one element and one compound

Question 3

Some students are using samples of different substances for a lab investigation. They plan to observe the physical properties of each substance and record their observations in a table like the one below. Which of the substances observed are elements?

Accepted Answer

$	ext {S, Fe, O}_2,{	ext{Sr}}$  and $	ext{Al}$

Answer

$	ext N_2 	ext O_4, 	ext {Fe}, 	ext{Sr}$ , and $	ext{Al}$

Answer

$	ext {S, O}_2,$  and $	ext{LiF}$

Answer

$	ext N_2 	ext O_4, 	ext O_2$ , and $	ext{LiF }$

Question 4

Which is the BEST example of a pure substance?

Accepted Answer

gold

Answer

air

Answer

milk

Answer

peanuts

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