Science : Study Points
1. Water boils at 100°C under normal atmospheric pressure.
Explanation: Water changes from liquid to vapor at 100°C under standard pressure (1 atmosphere). This is called the boiling point, where heat energy breaks molecular bonds, forming steam.
2. The basic unit of life is the cell.
Explanation: The cell is the smallest structural and functional unit of life. It performs essential functions like respiration, growth, and reproduction, forming tissues and organs in all living organisms.
3. The gas used by plants for photosynthesis is carbon dioxide.
Explanation: Green plants take in carbon dioxide from the air and, using sunlight and chlorophyll, convert it into glucose and oxygen during photosynthesis, which provides food and releases oxygen.
4. The Earth revolves around the Sun.
Explanation: Earth completes one revolution around the Sun in about 365 days. This movement causes changes in seasons and defines the duration of a year.
5. Metals are good conductors of electricity.
Explanation: Metals have free electrons that allow electric current to flow easily through them. This property makes them useful in wires, circuits, and electrical appliances.
6. The hardest natural substance is diamond.
Explanation: Diamond is made of tightly bonded carbon atoms in a crystal structure. Its extreme hardness makes it ideal for cutting, drilling, and jewelry purposes.
7. Blood is pumped by the heart.
Explanation: The heart continuously pumps oxygenated blood through arteries and receives deoxygenated blood through veins, maintaining circulation and supplying oxygen and nutrients to body tissues.
8. A substance with a pH less than 7 is called an acid.
Explanation: Acids have higher hydrogen ion concentration. They taste sour, react with metals, and turn blue litmus red. Examples include lemon juice and hydrochloric acid.
9. The part of the plant that absorbs water is the root.
Explanation: Roots absorb water and minerals from the soil through root hairs. They also anchor the plant firmly and transport nutrients to the stem and leaves.
10. The process of changing a solid directly into a gas is called sublimation.
Explanation: In sublimation, a solid changes directly into vapor without becoming liquid. Examples include camphor, naphthalene, and dry ice (solid carbon dioxide).
11. The force that pulls objects toward the Earth is gravity.
Explanation: Gravity is the natural force of attraction between Earth and all objects. It keeps us grounded and causes objects to fall when dropped.
12. The process of heat transfer through liquids and gases is called convection.
Explanation: Convection occurs when warmer parts of a fluid rise and cooler parts sink, forming a circulation current that transfers heat energy efficiently.
13. The planet known as the "Red Planet" is Mars.
Explanation: Mars appears red because of iron oxide on its surface. It is the fourth planet from the Sun and has polar ice caps and thin atmosphere.
14. The three states of matter are solid, liquid, and gas.
Explanation: Matter exists mainly in three forms. Solids have fixed shape, liquids flow and take container shape, gases expand freely to fill space.
15. The energy from the Sun comes in the form of solar energy.
Explanation: Solar energy is radiant light and heat from the Sun. It supports life, drives photosynthesis, and is harnessed for electricity through solar panels.