Midterm Review Questions on Density and Acids

Water consists of one oxygen atom and two hydrogen atoms. Between water molecules, weak hydrogen bonds form due to the attraction between negatively charged oxygen and positively charged hydrogen atoms. When temperatures fall below 4°C, water's density decreases as oxygen atoms repel each other. Ice floats because it has a higher volume and lower density than water.
水由一个氧原子和两个氢原子组成。由于带负电的氧和带正电的氢原子之间的吸引力，水分子之间形成弱氢键。当温度低于 4°C 时，水的密度会因氧原子相互排斥而降低。冰之所以能漂浮，是因为它的体积比水大，密度比水低。

What is water made up of?

• Two oxygen atoms and one hydrogen atom

• One oxygen atom and two hydrogen atoms

• Two oxygen atoms and two hydrogen atoms

• One hydrogen atom and two oxygen atoms

What causes the weak hydrogen bonds between water molecules?

• The attraction between negatively charged hydrogen atoms

• The attraction between positively charged oxygen atoms

• The attraction between negatively charged oxygen and positively charged hydrogen atoms

• The repulsion between hydrogen and oxygen atoms

Water consists of one oxygen atom and two hydrogen atoms. Between water molecules, weak hydrogen bonds form due to the attraction between negatively charged oxygen and positively charged hydrogen atoms. When temperatures fall below 4°C, water's density decreases as oxygen atoms repel each other. Ice floats because it has a higher volume and lower density than water.
水由一个氧原子和两个氢原子组成。由于带负电的氧和带正电的氢原子之间的吸引力，水分子之间形成弱氢键。当温度低于 4°C 时，水的密度会因氧原子相互排斥而降低。冰之所以能漂浮，是因为它的体积比水大，密度比水低。

What happens to water molecules as the temperature drops below 4°C?

• They come closer, increasing density

• The density continues to increase

• The density decreases because oxygen atoms repel each other

• The water molecules break apart

Why does ice have a lower density than water?

• The hydrogen bonds in ice are weak

• Oxygen atoms in ice are closer together

• The molecules in ice are packed tightly

• Oxygen atoms in ice are spread farther apart, leaving more space between molecules

Water consists of one oxygen atom and two hydrogen atoms. Between water molecules, weak hydrogen bonds form due to the attraction between negatively charged oxygen and positively charged hydrogen atoms. When temperatures fall below 4°C, water's density decreases as oxygen atoms repel each other. Ice floats because it has a higher volume and lower density than water.
水由一个氧原子和两个氢原子组成。由于带负电的氧和带正电的氢原子之间的吸引力，水分子之间形成弱氢键。当温度低于 4°C 时，水的密度会因氧原子相互排斥而降低。冰之所以能漂浮，是因为它的体积比水大，密度比水低。

Why does ice float on water?

• Ice is lighter because it contains fewer hydrogen atoms

• Ice has a higher volume and lower density than water

• Ice molecules are denser than water molecules

• Ice has stronger hydrogen bonds than liquid water

Lemons taste sour because they contain citric acid, while the sourness in vinegar is due to ethanoic acid. Bathroom cleaners are alkaline, with ammonia giving them this property. To reduce acidity in garden soil, ground limestone, or calcium carbonate, can be added, which is also the main component in chalk. According to the Arrhenius theory, acids in water increase H+ ions, while alkalis produce OH– ions. For example, hydrochloric acid (HCl) dissociates into H+ and Cl– ions in water. Acidic substances have a pH below 7, and neutralization between acids and bases of equal strength produces salt and water. 柠檬之所以有酸味是因为它们含有柠檬酸，而醋的酸味则是因为含有乙酸。浴室清洁剂是碱性的，氨赋予了它们这种特性。为了降低花园土壤的酸度，可以添加磨碎的石灰石或碳酸钙，这也是白垩的主要成分。根据阿累尼乌斯理论，水中的酸会增加 H+ 离子，而碱会产生 OH- 离子。例如，盐酸 (HCl) 在水中分解成 H+ 和 Cl- 离子。酸性物质的pH值低于7，等强度的酸和碱之间的中和会产生盐和水。

Why does lemon taste sour?

• Because of ethanoic acid

• Because of citric acid

• Because of calcium carbonate

• Because of ammonia

Which acid is responsible for the sour taste in vinegar?

• Citric acid

• Hydrochloric acid

• Ethanoic acid

• Sulfuric acid

Lemons taste sour because they contain citric acid, while the sourness in vinegar is due to ethanoic acid. Bathroom cleaners are alkaline, with ammonia giving them this property. To reduce acidity in garden soil, ground limestone, or calcium carbonate, can be added, which is also the main component in chalk. According to the Arrhenius theory, acids in water increase H+ ions, while alkalis produce OH– ions. For example, hydrochloric acid (HCl) dissociates into H+ and Cl– ions in water. Acidic substances have a pH below 7, and neutralization between acids and bases of equal strength produces salt and water. 柠檬之所以有酸味是因为它们含有柠檬酸，而醋的酸味则是因为含有乙酸。浴室清洁剂是碱性的，氨赋予了它们这种特性。为了降低花园土壤的酸度，可以添加磨碎的石灰石或碳酸钙，这也是白垩的主要成分。根据阿累尼乌斯理论，水中的酸会增加 H+ 离子，而碱会产生 OH- 离子。例如，盐酸 (HCl) 在水中分解成 H+ 和 Cl- 离子。酸性物质的pH值低于7，等强度的酸和碱之间的中和会产生盐和水。

Bathroom cleaner is alkaline due to the presence of which substance?

• Citric acid

• Calcium carbonate

• Ethanoic acid

• Ammonia

What can be used to make garden soil less acidic?

• Ammonia

• Citric acid

• Ground limestone (calcium carbonate)

• Ethanoic acid

Lemons taste sour because they contain citric acid, while the sourness in vinegar is due to ethanoic acid. Bathroom cleaners are alkaline, with ammonia giving them this property. To reduce acidity in garden soil, ground limestone, or calcium carbonate, can be added, which is also the main component in chalk. According to the Arrhenius theory, acids in water increase H+ ions, while alkalis produce OH– ions. For example, hydrochloric acid (HCl) dissociates into H+ and Cl– ions in water. Acidic substances have a pH below 7, and neutralization between acids and bases of equal strength produces salt and water. 柠檬之所以有酸味是因为它们含有柠檬酸，而醋的酸味则是因为含有乙酸。浴室清洁剂是碱性的，氨赋予了它们这种特性。为了降低花园土壤的酸度，可以添加磨碎的石灰石或碳酸钙，这也是白垩的主要成分。根据阿累尼乌斯理论，水中的酸会增加 H+ 离子，而碱会产生 OH- 离子。例如，盐酸 (HCl) 在水中分解成 H+ 和 Cl- 离子。酸性物质的pH值低于7，等强度的酸和碱之间的中和会产生盐和水。

What is the primary component of chalk?

• Ammonia

• Citric acid

• Calcium carbonate

• Ethanoic acid