name: tadarrian crump 5th period
properties of water and ph

1. write the chemical equation for water, and draw a stick model of a water molecule. show polarity by label positive and negatively charged regions of the molecule.

3. what kind of bond holds the hydrogen to the oxygen in one water molecule?

4. what kind of bonds can hold two separate water molecules together?

5. what is a polar molecule?

6. the polarity of water allows it to ____________ most substances. because of this it is referred to as the ______________________.

7. water molecules stick to other water molecules. this property is called ______________.

8. water molecules stick to other water molecules. this property is called ______________.

9. why does ice float on water?

10. why is it important that water resists temperature changes?

critical reading: ph

when some substances dissolve in water they break up into ions. a compound that releases a hydrogen ion (a proton) when it dissolves in water is an acid. bases are compounds that remove, or accept, hydrogen ions. a solution’s acidity, or its hydrogen ion concentration, is measured on the ph scale. an acid has a low ph (ph below 7) and a high hydrogen ion concentration. a base has a high ph (ph above 7) and a low hydrogen ion concentration. organisms must maintain a stable ph. even a small change in ph can disrupt many biological processes.

11. describe what the ph of a substance is measuring.

12. draw the ph scale and label acid, neutral, and base.

13. what has more hydrogen ions, acids or bases?

Question

name: tadarrian crump 5th period
properties of water and ph

1. write the chemical equation for water, and draw a stick model of a water molecule. show polarity by label positive and negatively charged regions of the molecule.

3. what kind of bond holds the hydrogen to the oxygen in one water molecule?

4. what kind of bonds can hold two separate water molecules together?

5. what is a polar molecule?

6. the polarity of water allows it to ____________ most substances. because of this it is referred to as the ______________________.

7. water molecules stick to other water molecules. this property is called ______________.

8. water molecules stick to other water molecules. this property is called ______________.

9. why does ice float on water?

10. why is it important that water resists temperature changes?

critical reading: ph

when some substances dissolve in water they break up into ions. a compound that releases a hydrogen ion (a proton) when it dissolves in water is an acid. bases are compounds that remove, or accept, hydrogen ions. a solution’s acidity, or its hydrogen ion concentration, is measured on the ph scale. an acid has a low ph (ph below 7) and a high hydrogen ion concentration. a base has a high ph (ph above 7) and a low hydrogen ion concentration. organisms must maintain a stable ph. even a small change in ph can disrupt many biological processes.

11. describe what the ph of a substance is measuring.

12. draw the ph scale and label acid, neutral, and base.

13. what has more hydrogen ions, acids or bases?

Accepted Answer

### Question 3
# Brief Explanations:
In a water molecule ($H_2O$), the bond between hydrogen (H) and oxygen (O) within one molecule is a covalent bond. A covalent bond is formed when atoms share electrons. In water, the oxygen and each hydrogen share electrons to achieve a stable electron configuration.
# Answer:
Covalent bond

### Question 4
# Brief Explanations:
Two separate water molecules are held together by hydrogen bonds. A hydrogen bond is an intermolecular force (a force between molecules) that occurs when a hydrogen atom, which is covalently bonded to a highly electronegative atom (like oxygen in water), is attracted to another electronegative atom (like the oxygen in another water molecule).
# Answer:
Hydrogen bonds

### Question 5
# Brief Explanations:
A polar molecule is a molecule in which there is an unequal distribution of electron density, resulting in a partial positive charge on one part of the molecule and a partial negative charge on another part. This occurs when there is a significant difference in electronegativity between the atoms in the molecule, and the molecular geometry is such that the dipole moments do not cancel out. For example, in water ($H_2O$), the oxygen is more electronegative than hydrogen, so the electrons in the O - H bonds are pulled closer to the oxygen, giving the oxygen a partial negative charge ($\delta^-$) and the hydrogens partial positive charges ($\delta^+$).
# Answer:
A molecule with an unequal distribution of electron density, having a partial positive and a partial negative region (e.g., water, where oxygen is partially negative and hydrogens are partially positive due to electronegativity differences and molecular geometry).

### Question 6
# Brief Explanations:
The polarity of water allows it to dissolve most substances (especially polar and ionic substances). Because of its ability to dissolve many substances, water is referred to as the universal solvent. Polar water molecules can interact with polar solute molecules (through dipole - dipole interactions) or ionic solutes (by surrounding the ions, with the positive part of water attracting negative ions and the negative part attracting positive ions).
# Answer:
dissolve; universal solvent

### Question 7 (Note: Likely a typo, probably "Water molecules stick to other types of molecules" or a repeat, but assuming it's "Water molecules stick to other water molecules" as in question 8, but if it's "stick to other molecules" it's adhesion. If it's a repeat of question 8, it's cohesion. Given the context, if it's about sticking to other water molecules, same as question 8)
# Brief Explanations:
When water molecules stick to other water molecules, this property is called cohesion. Cohesion is due to the hydrogen bonds between water molecules. The hydrogen bonds cause the water molecules to be attracted to one another, leading to this "sticking" effect.
# Answer:
Cohesion

### Question 8
# Brief Explanations:
When water molecules stick to other water molecules, this property is called cohesion. The hydrogen bonds between the partially positive hydrogen atoms of one water molecule and the partially negative oxygen atoms of other water molecules are responsible for this attractive force between water molecules.
# Answer:
Cohesion

### Question 9
# Brief Explanations:
Ice floats on water because the density of ice is less than the density of liquid water. When water freezes into ice, the water molecules form a crystalline structure (a hexagonal lattice) due to hydrogen bonding. In this structure, the water molecules are spaced further apart than in liquid water. Since density is mass per unit volume, and the same mass of water occupies a larger volume in the solid (ice) state, the density of ice ($\approx0.917\ g/cm^3$) is less than that of liquid water ($\approx1\ g/cm^3$). Objects with a lower density than the fluid they are in will float.
# Answer:
Ice has a lower density than liquid water because water molecules in ice form a hexagonal lattice structure with more space between them (due to hydrogen bonding), so ice floats.

### Question 10
# Brief Explanations:
It is important that water resists temperature changes (has a high specific heat capacity) because it helps to regulate temperatures in the environment and in organisms. For example, in the environment, large bodies of water (like oceans, lakes) can absorb and release large amounts of heat with only small changes in temperature. This moderates the climate of nearby land areas. In organisms, water - based cells and tissues can maintain a relatively stable internal temperature, which is crucial for the proper functioning of enzymes and other biological processes that are sensitive to temperature changes.
# Answer:
It regulates environmental and biological temperatures (e.g., moderates climate, stabilizes organism internal temp for enzyme function).

### Question 11
# Brief Explanations:
The pH of a substance measures the acidity (or alkalinity) of a solution, specifically the concentration of hydrogen ions ($H^+$) in the solution. Mathematically, $pH = -\log_{10}[H^+]$, where $[H^+]$ is the molar concentration of hydrogen ions. A low pH (below 7) indicates a high hydrogen ion concentration (an acidic solution), and a high pH (above 7) indicates a low hydrogen ion concentration (a basic solution), with a pH of 7 being neutral.
# Answer:
The pH of a substance measures the hydrogen ion ($H^+$) concentration (acidity/alkalinity) of a solution, calculated as $pH = -\log_{10}[H^+]$.

### Question 12
# Brief Explanations:
The pH scale ranges from 0 to 14.
- A pH of 7 is neutral (e.g., pure water at 25°C has a pH of 7).
- pH values less than 7 are acidic (e.g., lemon juice has a pH around 2 - 3).
- pH values greater than 7 are basic (e.g., baking soda solution has a pH around 8 - 9).

To draw the pH scale:
1. Draw a horizontal line.
2. Label the left - most end as 0, the middle as 7, and the right - most end as 14.
3. Label the region from 0 to 7 as "Acid", the point at 7 as "Neutral", and the region from 7 to 14 as "Base".
# Answer:
The pH scale is a horizontal line from 0 (left, acidic) to 14 (right, basic), with 7 in the middle (neutral). Label: 0 - 7: Acid; 7: Neutral; 7 - 14: Base.

### Question 13
# Brief Explanations:
Acids have more hydrogen ions than bases. By definition, an acid is a compound that releases a hydrogen ion ($H^+$) when it dissolves in water, so acidic solutions have a high concentration of $H^+$ ions. Bases, on the other hand, either accept $H^+$ ions or release hydroxide ions ($OH^-$), and they have a low concentration of $H^+$ ions. Since $pH = -\log_{10}[H^+]$, a lower pH (acidic) corresponds to a higher $[H^+]$.
# Answer:
Acids

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