Name any four devices that work on the heating effect of electric current.

Here are the answers to the questions:

11. Four devices that work on the heating effect of electric current are:

    • Electric heater
    • Electric iron
    • Electric kettle
    • Incandescent light bulb

12. Four healthy lifestyle practices are:

    • Eating a balanced diet
    • Regular physical exercise
    • Getting adequate sleep
    • Avoiding smoking and excessive alcohol consumption

13. A neuron (nerve cell) typically consists of three main parts:

    • Cell body (soma): Contains the nucleus and other organelles.
    • Dendrites: Branch-like extensions that receive signals from other neurons.
    • Axon: A long, slender projection that transmits signals away from the cell body to other neurons, muscles, or glands. It is often covered by a myelin sheath.

14. Experiment to demonstrate intermolecular space in liquids:

    • Step 1: Take a measuring cylinder and fill it with 50 mL of water.
    • Step 2: Add 50 mL of alcohol (e.g., ethanol) to the same measuring cylinder containing water.
    • Step 3: Observe the total volume.
    • Observation: The total volume of the mixture will be less than 100 mL (e.g., around 96 mL).
    • Conclusion: This reduction in volume indicates that the alcohol molecules have occupied the empty intermolecular spaces between the water molecules, demonstrating that liquids have intermolecular spaces.

15. A thunderstorm is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder.

    • Formation:
      • Step 1: Warm, moist air rises: Warm, moist air near the Earth's surface begins to rise rapidly.
      • Step 2: Condensation and cloud formation: As the air rises, it cools, and the water vapor condenses to form cumulus clouds.
      • Step 3: Further development: If the updraft continues, the cloud grows vertically into a cumulonimbus cloud (thunderhead). Water droplets and ice crystals within the cloud collide, creating electrical charges.
      • Step 4: Precipitation and lightning: When the electrical charge separation becomes large enough, lightning occurs, followed by thunder. Precipitation (rain, hail) falls from the cloud, creating downdrafts.

16. The weight of an object on the Moon is one-sixth of its weight on the Earth because weight is a measure of the gravitational force acting on an object, and the Moon's gravitational acceleration is approximately one-sixth that of Earth's.

    • Weight is calculated as $W = m \times g$, where $m$ is mass and $g$ is gravitational acceleration. Since $g_{\text{Moon}} \approx \frac{1}{6} g_{\text{Earth}}$, the weight on the Moon is also approximately one-sixth.
    • No, the mass of the object does not become one-sixth of its mass on Earth. Mass is an intrinsic property of an object and remains constant regardless of its location or the gravitational field.

17. Rechargeable batteries are secondary cells that can be recharged by applying an external electrical current, which reverses the chemical reactions that occur during discharge.

    • Uses: They are used in devices that require frequent power and where disposable batteries would be costly or environmentally wasteful.
    • Two devices:
      • Mobile phones
      • Laptops

18. Four measures to prevent the spread of a cold from a child in school to other children:

    • Encourage frequent handwashing: Teach children to wash their hands thoroughly with soap and water, especially after coughing, sneezing, or blowing their nose.
    • Promote respiratory hygiene: Teach children to cover their mouth and nose with a tissue or their elbow when coughing or sneezing.
    • Isolate the sick child: If possible, keep the sick child at home until they are no longer contagious to prevent further spread.
    • Clean and disinfect surfaces: Regularly clean and disinfect frequently touched surfaces in the classroom (e.g., desks, doorknobs, toys).

19. A. Three differences between plant cells and animal cells:

    • Cell Wall: Plant cells have a rigid cell wall outside the cell membrane, while animal cells do not.
    • Chloroplasts: Plant cells contain chloroplasts for photosynthesis, while animal cells do not.
    • Vacuole: Plant cells typically have a large, central vacuole, whereas animal cells have small, temporary, or no vacuoles.

20. B. A plant cell diagram would typically include and label the following parts:

    • Cell Wall
    • Cell Membrane
    • Cytoplasm
    • Nucleus (with Nucleolus)
    • Mitochondria
    • Chloroplasts
    • Large Central Vacuole
    • Endoplasmic Reticulum (Rough and Smooth)
    • Ribosomes
    • Golgi Apparatus (or Golgi complex/body)