1. compare a molecule of oxygen (o₂) and a molecule of water (h₂o)
2. which is a compound?
a) o₂
b) co₂
c) he
d) h
3. fill in the blank: an element is made of only one kind of ____.
4. how many atoms of each element are in the formula c₆h₁₂o₆?
5. use the periodic table: what element has the symbol na?
6. in the formula h₂o, how many oxygen atoms are there?
7. is ice melting a physical or chemical change? why?
8. baking a cake is a ____ change.
9. which is evidence of a chemical change?
a) change in shape
b) formation of bubbles
c) breaking into pieces
d) dissolving
10. in a saltwater solution, which is the solute? which is the solvent?
11. what happens to concentration if you add more water to a sugary drink?

Question

1. compare a molecule of oxygen (o₂) and a molecule of water (h₂o)
2. which is a compound?
   a) o₂
   b) co₂
   c) he
   d) h
3. fill in the blank: an element is made of only one kind of ____.
4. how many atoms of each element are in the formula c₆h₁₂o₆?
5. use the periodic table: what element has the symbol na?
6. in the formula h₂o, how many oxygen atoms are there?
7. is ice melting a physical or chemical change? why?
8. baking a cake is a ____ change.
9. which is evidence of a chemical change?
   a) change in shape
   b) formation of bubbles
   c) breaking into pieces
   d) dissolving
10. in a saltwater solution, which is the solute? which is the solvent?
11. what happens to concentration if you add more water to a sugary drink?

Accepted Answer

### Question 2
# Brief Explanations:
A compound is a substance made of two or more different elements chemically bonded. $O_2$ has one element (oxygen), He is an element, H is an atom. $CO_2$ has carbon and oxygen, so it's a compound.
# Answer:
B) $CO_2$

### Question 3
# Brief Explanations:
By definition, an element consists of only one kind of atom.
# Answer:
atom

### Question 4
# Explanation:
## Step1: Identify elements in $C_6H_{12}O_6$
The formula has C (carbon), H (hydrogen), O (oxygen).
## Step2: Count atoms for each
For C: subscript 6 → 6 atoms.
For H: subscript 12 → 12 atoms.
For O: subscript 6 → 6 atoms.
# Answer:
Carbon: 6 atoms, Hydrogen: 12 atoms, Oxygen: 6 atoms

### Question 5
# Brief Explanations:
From the Periodic Table, the symbol Na corresponds to Sodium.
# Answer:
Sodium

### Question 6
# Explanation:
## Step1: Analyze $H_2O$ formula
In a chemical formula, the subscript after an element symbol shows the number of atoms. For O in $H_2O$, the subscript is 1 (implied if no subscript).
# Answer:
1

### Question 7
# Brief Explanations:
Ice melting is a physical change because it changes state (solid to liquid) but the substance (water) remains the same; no new substance is formed.
# Answer:
Physical change. Because ice (solid water) becomes liquid water—no new substance is created, just a state change.

### Question 8
# Brief Explanations:
Baking a cake involves chemical reactions (e.g., baking powder reacting, proteins denaturing) that form new substances, so it's a chemical change.
# Answer:
chemical

### Question 9
# Brief Explanations:
A change in shape (A), breaking (C), or dissolving (D) are physical changes. Formation of bubbles (e.g., gas from a reaction) indicates a new substance, so it's chemical change evidence.
# Answer:
B) Formation of bubbles

### Question 10
# Brief Explanations:
In a solution, the solute is the substance dissolved (salt, $NaCl$), and the solvent is the substance doing the dissolving (water, $H_2O$).
# Answer:
Solute: Salt (NaCl); Solvent: Water (H₂O)

### Question 11
# Explanation:
## Step1: Recall concentration formula
Concentration (e.g., molarity) is $\frac{\text{amount of solute}}{\text{amount of solution}}$.
## Step2: Analyze adding water
Adding more water (solvent) increases the amount of solution, while the solute (sugar) amount stays the same. So $\frac{\text{solute}}{\text{solution}}$ decreases.
# Answer:
The concentration decreases (becomes more dilute) because the amount of solvent (water) increases while the solute (sugar) amount remains constant.

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QUESTION IMAGE

Question

Explanation:

Question 2

Step1: Identify elements in \(C_6H_{12}O_6\)

Step2: Count atoms for each

Answer:

Question 3