General Science Review of Grade 8 topics worksheet - Free Printable

Let's solve each question step by step:

---

Question 1: Which is NOT an example of kinetic energy?

Options:
- A. Turning a windmill
- B. A stretched rubber band
- C. A spiral spring
- D. Water behind a dam

#### Explanation:
- Kinetic energy is the energy possessed by an object due to its motion.
- Let's analyze each option:
- A. Turning a windmill: The windmill is in motion, so it has kinetic energy.
- B. A stretched rubber band: A stretched rubber band has potential energy (elastic potential energy), not kinetic energy, because it is not moving.
- C. A spiral spring: A spiral spring that is compressed or stretched has potential energy, not kinetic energy, as it is not moving.
- D. Water behind a dam: The water is stationary and has potential energy (gravitational potential energy), not kinetic energy.

#### Correct Answer:
The options B and C are examples of potential energy, but since the question asks for the one that is NOT an example of kinetic energy, the best choice is B because it is explicitly mentioned as a stretched rubber band, which has elastic potential energy.

Answer: B

---

Question 2: Which simple machine makes up a pair of scissors?

Options:
- A. First class lever only
- B. First class lever and wedge
- C. Second class lever and wedge
- D. Wedge only

#### Explanation:
- Scissors are a combination of two simple machines:
1. First class lever: The scissors have a pivot point (fulcrum) in the middle, with effort applied at one end and resistance at the other. This is characteristic of a first-class lever.
2. Wedge: The cutting edges of the scissors act as wedges, which help in cutting materials by applying force over a small area.

#### Correct Answer:
Since scissors use both a first-class lever and a wedge, the correct answer is B.

Answer: B

---

Question 3: What happens when the temperature of water is \(0^\circ \text{C}\)? It becomes a:

Options:
- A. gas
- B. liquid
- C. plasma
- D. solid

#### Explanation:
- At \(0^\circ \text{C}\), water can exist in multiple states depending on the pressure and conditions:
- Freezing Point: At standard atmospheric pressure (\(1 \text{ atm}\)), water freezes at \(0^\circ \text{C}\) and turns into ice (solid).
- Melting Point: Similarly, ice melts at \(0^\circ \text{C}\) under standard conditions to become liquid water.
- Triple Point: At specific conditions, water can exist in all three states (solid, liquid, and gas) simultaneously, but this is not relevant here.

Given the context of the question, it is asking about the state of water at \(0^\circ \text{C}\) under normal conditions, which is typically when it transitions between liquid and solid.

#### Correct Answer:
At \(0^\circ \text{C}\), water can be either liquid or solid, but the most common interpretation in this context is that it becomes solid (ice).

Answer: D

---

Final Answers:

1. B
2. B
3. D

Boxed Final Answer:
\[
\boxed{B, B, D}
\]