Science Exam Questions And Answers

Explanation
Water returns to the Earth as precipitation, which includes rain, snow, sleet, or hail. Condensation is actually a step in the water cycle where water vapor cools and turns back into liquid water, forming clouds. These clouds eventually release their moisture as precipitation, which then falls back to the Earth. Therefore, the statement that water returns to the Earth as condensation is incorrect.

Explanation
Water vapor in the atmosphere condenses to form clouds. This is true because when warm air rises, it expands and cools. As the air cools, it reaches its dew point, which is the temperature at which the air is saturated and cannot hold any more water vapor. At this point, the water vapor condenses into tiny water droplets or ice crystals, forming clouds. These clouds can then lead to precipitation such as rain, snow, or hail. So, the statement is correct.

Explanation
Precipitation refers to the process by which water vapor in the atmosphere condenses and falls to the Earth's surface as rain, snow, sleet, or hail. It is the primary source of fresh water on Earth. Therefore, the statement that the source of almost all fresh water on Earth's surface is precipitation is true.

Explanation
Water can exist in three states: liquid, gas, and solid. In the liquid state, water is in its typical form that we see and use every day. In the gas state, water vaporizes and becomes invisible, such as when it evaporates from a boiling pot. In the solid state, water freezes and becomes ice. These three states are well-known and scientifically proven, making the statement "The three states of water are liquid, gas, and solid" true.

Explanation
The correct answer is friction. Friction is the force that opposes the motion of objects in contact with each other. In the case of a ball rolling on the ground, as it moves, there is friction between the ball and the ground. This friction gradually slows down the ball's motion until it eventually comes to a stop. Without friction, the ball would continue rolling indefinitely.

Explanation
The force exerted by magnets is an example of a non-contact force because it can act on objects without physically touching them. Magnets have a magnetic field that can attract or repel other magnetic objects from a distance. This force can be observed when two magnets are brought near each other and they either attract or repel each other without any direct contact. Therefore, the force exerted by magnets is a non-contact force.

Explanation
The force of friction is a contact force because it occurs when two surfaces are in contact with each other and it opposes the motion or tendency of motion between them. It is caused by the irregularities in the surfaces and the interlocking of the microscopic bumps and ridges on the surfaces. This force is experienced in everyday situations such as walking, driving a car, or sliding objects on a table.

Explanation
An irregular surface will have greater friction because irregularities in the surface create more points of contact between the objects in contact. This increased contact leads to more resistance to motion, resulting in greater friction.

Explanation
The force of friction depends on the smoothness of the surface because a smoother surface allows for less friction. It also depends on the roughness of the surface because a rougher surface creates more friction. Additionally, the force of friction is influenced by the inclination of the surface because a steeper incline increases friction. Therefore, all of the given options affect the force of friction.