3. fill in the blank: an element is made of only one kind of blank.
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

3. fill in the blank: an element is made of only one kind of blank.
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 3
# Brief Explanations:
An element is a pure substance that consists of only one kind of atom. By definition, elements are made up of identical atoms (or in some cases, molecules of the same atom, like $O_2$ for oxygen, but the fundamental unit is the atom of that element).
# Answer:
atom

### Question 4
# Explanation:
## Step1: Identify each element and its subscript
In the formula $C_6H_{12}O_6$, the elements are Carbon (C), Hydrogen (H), and Oxygen (O). The subscript next to each element symbol indicates the number of atoms of that element.
## Step2: State the number of atoms for each element
For Carbon (C), the subscript is 6, so there are 6 carbon atoms. For Hydrogen (H), the subscript is 12, so there are 12 hydrogen atoms. For Oxygen (O), the subscript is 6, so there are 6 oxygen atoms.
# Answer:
Carbon: 6 atoms, Hydrogen: 12 atoms, Oxygen: 6 atoms

### Question 5
# Brief Explanations:
Using the Periodic Table, the symbol "Na" corresponds to the element Sodium. The Periodic Table lists elements with their symbols, and "Na" is derived from the Latin name "Natrium" for Sodium.
# Answer:
Sodium

### Question 6
# Explanation:
## Step1: Analyze the formula $H_2O$
In a chemical formula, the subscript after an element symbol indicates the number of atoms of that element. In $H_2O$, the symbol for oxygen is O, and its subscript is 1 (when no subscript is written, it is assumed to be 1).
## Step2: Determine the number of oxygen atoms
So, in $H_2O$, there is 1 oxygen atom.
# Answer:
1

### Question 7
# Brief Explanations:
Ice melting is a physical change. A physical change is a change in which the substance's chemical identity remains the same, only its physical state (like solid, liquid, gas) changes. When ice (solid water) melts, it becomes liquid water ($H_2O$ remains $H_2O$); no new substance is formed, and the change is reversible (liquid water can be frozen back to ice).
# Answer:
Physical change. Because ice (solid water) melts to form liquid water, and the chemical composition ($H_2O$) remains the same; no new substance is created, and the change is reversible.

### Question 8
# Brief Explanations:
Baking a cake involves chemical reactions (like the reaction of baking powder, proteins denaturing, sugars caramelizing). New substances are formed (e.g., the cake's structure, flavor compounds), and the change is irreversible. So it is a chemical change.
# Answer:
chemical

### Question 9
# Brief Explanations:
- Option A: Change in shape is a physical change (e.g., bending a wire), no new substance.
- Option B: Formation of bubbles can indicate a gas being produced, which is often a sign of a chemical reaction (e.g., baking soda reacting with vinegar produces $CO_2$ bubbles).
- Option C: Breaking into pieces is a physical change (e.g., breaking a glass), no new substance.
- Option D: Dissolving is usually a physical change (e.g., salt dissolving in water, the salt can be recovered by evaporation).

So formation of bubbles is evidence of a chemical change.
# Answer:
B. Formation of bubbles

### Question 10
# Brief Explanations:
In a solution, the solute is the substance that is dissolved, and the solvent is the substance that does the dissolving (usually present in a larger amount). In saltwater, salt (sodium chloride, $NaCl$) is dissolved in water ($H_2O$). So salt is the solute, and water is the solvent.
# Answer:
Solute: Salt (sodium chloride, $NaCl$); Solvent: Water ($H_2O$)

### Question 11
# Explanation:
## Step1: Recall the definition of concentration
Concentration is the amount of solute (sugar, in this case) relative to the amount of solvent (water) or solution. A common way to think about it is "how much solute is in a given amount of solvent/solution."
## Step2: Analyze the effect of adding more water
If we add more water (solvent) to a sugary drink (solution with sugar as solute), the amount of solute (sugar) remains the same, but the amount of solvent (water) increases. So the ratio of solute to solvent (or solution) decreases.
## Step3: Conclude the change in concentration
Since concentration depends on the amount of solute relative to the solvent/solution, adding more water (increasing solvent) while keeping solute constant will decrease the concentration (the drink becomes less sweet, more diluted).
# Answer:
The concentration decreases (the solution becomes more diluted) because the amount of solute (sugar) remains the same while the amount of solvent (water) increases, so the ratio of solute to solvent/solution decreases.

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QUESTION IMAGE

Question

Explanation:

Question 3

Step1: Identify each element and its subscript

Step2: State the number of atoms for each element

Answer:

Question 4