1.
Which two elements make up water?
Correct Answer
A. Hydrogen and oxygen
Explanation
Water is a compound composed of two elements, hydrogen and oxygen. The chemical formula for water is H2O, indicating that each water molecule consists of two hydrogen atoms bonded to one oxygen atom. Therefore, the correct answer is hydrogen and oxygen.
2.
Sound travels faster through water than air.
Correct Answer
A. True
Explanation
Sound travels faster through water than air because water is denser than air. The molecules in water are closer together, allowing sound waves to travel more quickly through the medium. In comparison, air molecules are more spread out, causing sound waves to move slower. This is why sound can be heard over longer distances underwater than in the air.
3.
How long can the average human survive without water?
Correct Answer
B. A few days
Explanation
The average human can survive without water for a few days. Water is essential for the body to function properly, and dehydration can lead to various health issues. The exact duration a person can survive without water depends on several factors such as temperature, activity level, and individual health. However, it is generally accepted that without water, the body can only sustain itself for a few days before severe dehydration sets in, causing organ failure and ultimately leading to death.
4.
At what temperature does water boil?
Correct Answer
B. 100 C
Explanation
Water boils at 100 degrees Celsius. This is the temperature at which the vapor pressure of water equals the atmospheric pressure, causing the liquid water to turn into water vapor. Boiling is a phase transition from the liquid to the gas phase, and it occurs at a specific temperature for each substance. In the case of water, it boils at 100 degrees Celsius under normal atmospheric conditions.
5.
When water is cooled, does it contract or expand?
Correct Answer
B. Expand
Explanation
When water is cooled, it expands. This is because water molecules form a unique structure known as a hydrogen bond. As the temperature decreases, the water molecules slow down and the hydrogen bonds become more stable, causing the water to expand. This expansion is why ice floats on water, as the solid form of water is less dense than the liquid form.
6.
At what temperature does water freeze?
Correct Answer
B. 0 C
Explanation
Water freezes at 0 degrees Celsius. This is the temperature at which water changes from a liquid state to a solid state, forming ice. At temperatures below 0 degrees Celsius, water molecules slow down and begin to arrange themselves into a crystal lattice structure, resulting in the formation of ice. Therefore, 0 degrees Celsius is the freezing point of water.
7.
What is the average pH level of pure water?
Correct Answer
C. 7
Explanation
The average pH level of pure water is 7 because water is considered neutral, with a pH of 7. A pH value below 7 indicates acidity, while a pH value above 7 indicates alkalinity. Since pure water is neither acidic nor alkaline, its pH level is 7.
8.
In which step of the water cycle does liquid water transform into gas?
Correct Answer
D. Evaporation
Explanation
Evaporation is the process in which liquid water transforms into gas. This occurs when heat is applied to the water, causing the water molecules to gain energy and become vapor. Evaporation is an important step in the water cycle, as it allows water to enter the atmosphere and eventually form clouds.
9.
What percentage of the Earth's water supply is fresh water?
Correct Answer
A. 3%
Explanation
Only 3% of the Earth's water supply is fresh water. The majority of the Earth's water is saltwater, making it unsuitable for human consumption or agricultural use. This limited availability of fresh water highlights the importance of conservation and sustainable use of this precious resource.
10.
What property of water allows it to stick to itself?
Correct Answer
C. Cohesion
Explanation
Cohesion is the property of water that allows it to stick to itself. This is due to the hydrogen bonding between water molecules. The positive end of one water molecule is attracted to the negative end of another, creating a cohesive force. This cohesive force is responsible for many important properties of water, such as surface tension and capillary action.