CAEC Life and Physical Sciences 2 — Questions and Answers
Question 1: What is the function of mitochondria in a cell?
- Protein synthesis
- Producing energy (ATP) through cellular respiration (Correct answer)
- Controlling cell division
- Storing genetic information
Correct answer: Producing energy (ATP) through cellular respiration
Mitochondria are the powerhouses of the cell, producing ATP through cellular respiration using oxygen and glucose.
Mitochondria are membrane-bound organelles found in eukaryotic cells. They perform cellular respiration, converting nutrients (primarily glucose) and oxygen into adenosine triphosphate (ATP), the cell's main energy currency. The process involves glycolysis, the citric acid cycle, and the electron transport chain. Because of their role in energy production, cells with high energy demands (like muscle cells) have more mitochondria.
Question 2: What is Newton's Second Law of Motion?
- An object at rest stays at rest unless acted upon by a force
- Force equals mass times acceleration (F = ma) (Correct answer)
- For every action there is an equal and opposite reaction
- Energy cannot be created or destroyed
Correct answer: Force equals mass times acceleration (F = ma)
Newton's Second Law states that the force acting on an object equals its mass multiplied by its acceleration (F = ma).
Newton's Second Law of Motion establishes a quantitative relationship between force, mass, and acceleration. Expressed as F = ma, it states that the net force applied to an object is equal to the product of its mass and the resulting acceleration. This means a larger force produces more acceleration, and a heavier object requires more force to achieve the same acceleration. This law is fundamental to classical mechanics and engineering.
Question 3: What is the process by which water vapour in the atmosphere cools and becomes liquid water?
- Evaporation
- Transpiration
- Condensation (Correct answer)
- Precipitation
Correct answer: Condensation
Condensation is the process by which water vapour cools and changes state from a gas to a liquid, forming clouds, fog, or dew.
Condensation occurs when water vapour in the atmosphere loses heat energy and changes into liquid water. This happens when warm, moist air cools to its dew point temperature. Condensation is responsible for cloud formation, morning dew, and fog. In the water cycle, condensation follows evaporation and precedes precipitation, making it a critical step in distributing freshwater across Earth's surface.
Question 4: Which of the following is an example of a chemical change?
- Ice melting into water
- Sugar dissolving in coffee
- Wood burning in a fire (Correct answer)
- Glass breaking
Correct answer: Wood burning in a fire
Burning wood is a chemical change because combustion produces new substances (carbon dioxide, water, and ash) with different properties.
A chemical change (chemical reaction) produces one or more new substances with different chemical properties from the original materials. Signs of a chemical change include the production of gas, a colour change, formation of a precipitate, release of light or heat, or an odour. Burning wood (combustion) transforms cellulose and lignin into carbon dioxide, water vapour, and ash — entirely new substances. Melting, dissolving, and breaking are physical changes because the composition of the substance does not change.
Question 5: What is the difference between an element and a compound?
- Elements are gases; compounds are solids
- An element contains only one type of atom; a compound contains two or more different elements chemically bonded together (Correct answer)
- Elements are natural; compounds are man-made
- An element is a mixture; a compound is a pure substance
Correct answer: An element contains only one type of atom; a compound contains two or more different elements chemically bonded together
An element consists of only one type of atom and cannot be broken down into simpler substances; a compound is formed when two or more elements chemically combine.
The periodic table lists all known elements — pure substances made of only one type of atom (e.g., oxygen, iron, gold). Compounds are formed when atoms of two or more different elements are chemically bonded in fixed ratios; for example, water (H₂O) is a compound of hydrogen and oxygen. Unlike mixtures, compounds have properties different from their constituent elements and can only be separated by chemical reactions, not physical means.
Question 6: Which type of rock is formed from cooled magma or lava?
- Sedimentary
- Metamorphic
- Igneous (Correct answer)
- Limestone
Correct answer: Igneous
Igneous rock forms when magma (below ground) or lava (above ground) cools and solidifies.
Igneous rocks form through the cooling and crystallization of molten rock (magma underground, lava on the surface). Examples include granite (formed deep underground, slow cooling, large crystals) and basalt (formed from surface lava, fast cooling, fine crystals). Igneous rocks are part of the rock cycle, alongside sedimentary rocks (formed from compressed sediments) and metamorphic rocks (formed when existing rocks are changed by heat and pressure).
CAEC Life and Physical Sciences 2
What is the function of mitochondria in a cell?