Science 7 Flashcards
What is the principle behind the working of a microwave oven?
A microwave oven works on the principle of dielectric heating. It uses microwave radiation to heat polar molecules in food, causing them to rotate and produce thermal energy (heat).
Explain the greenhouse effect.
The greenhouse effect is the process by which radiation from a planet’s atmosphere warms the planet’s surface to a temperature above what it would be without its atmosphere. This is due to gases in the atmosphere trapping heat from the sun.
What are the primary components of DNA?
The primary components of DNA are nucleotides, each consisting of a sugar (deoxyribose), a phosphate group, and one of four nitrogenous bases: adenine (A), cytosine (C), guanine (G), or thymine (T).
Describe the role of plate tectonics in shaping Earth’s surface.
Plate tectonics is the theory explaining the movement of the Earth’s plates. It describes how Earth’s surface is divided into several large and small plates that move over the Earth’s mantle, leading to earthquakes, volcanoes, and the formation of mountain ranges.
What is photosynthesis?
Photosynthesis is the process used by plants, algae, and certain bacteria to harness energy from sunlight and turn it into chemical energy.
Define the term ‘ecosystem’.
An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system.
How do magnets work?
Magnets work due to the motion of electric charges. Each magnet has a north and a south pole. Opposite poles attract each other, while like poles repel each other.
What is the difference between speed and velocity?
Speed is a scalar quantity that refers to how fast an object is moving, while velocity is a vector quantity that refers to the rate at which an object changes its position.
Describe the life cycle of a star.
The life cycle of a star includes formation in a nebula, a stable period of fusion (like our Sun), expansion into a red giant, and ultimately either collapsing into a white dwarf or exploding as a supernova, potentially forming a neutron star or black hole.
What is a black hole?
A black hole is a region of spacetime where gravity is so strong that nothing, not even light, can escape from it.
Explain the concept of biodiversity.
Biodiversity refers to the variety and variability of life on Earth, encompassing the diversity of species, their genetic makeup, and the ecosystems they form.
What causes seasons to change?
Seasons change due to the tilt of the Earth’s rotational axis away or towards the Sun as it travels through its year-long path around the Sun.
What is the difference between a virus and a bacterium?
A virus is a small infectious agent that replicates only inside the living cells of other organisms, while a bacterium is a type of microorganism that has a simple cellular structure without a nucleus and usually multiplies by cell division.
How does a plant absorb water and nutrients?
Plants absorb water and nutrients mainly through their roots via osmosis and diffusion. Water is drawn up through the plant from the roots to the leaves in a process known as transpiration.
What is the theory of relativity?
The theory of relativity, developed by Albert Einstein, comprises two interrelated theories: special relativity and general relativity. It introduced concepts of spacetime and the equivalence of mass and energy.
