Explain these mcqs simply

Question 1: Which of the following is NOT a characteristic of a good scientific hypothesis?

a) It is testable.

b) It is falsifiable.

c) It is complex.

d) It is based on observations.

The correct answer is c) It is complex.
A good scientific hypothesis should be testable (can be investigated), falsifiable (can be proven wrong), and based on observations. While a hypothesis might describe a complex phenomenon, the hypothesis itself should ideally be as simple as possible (parsimonious) while still explaining the observations. Complexity is not a desired characteristic; rather, it can make a hypothesis harder to test or falsify.

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Question 2: What is the primary function of the mitochondria in a eukaryotic cell?

a) Protein synthesis

b) Photosynthesis

c) ATP production

d) Waste removal

The correct answer is c) ATP production.
Mitochondria are often called the "powerhouses of the cell" because their primary function is to generate adenosine triphosphate (ATP) through cellular respiration, which is the main energy currency of the cell. Protein synthesis occurs on ribosomes, photosynthesis in chloroplasts (in plant cells), and waste removal is handled by lysosomes and vacuoles.

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Question 3: Which of the following is an example of a chemical change?

a) Melting ice

b) Dissolving sugar in water

c) Burning wood

d) Cutting paper

The correct answer is c) Burning wood.
A chemical change results in the formation of new substances with different chemical properties.

a) Melting ice is a physical change (water changes state from solid to liquid, but it's still $\ce{H2O}$).

b) Dissolving sugar in water is a physical change (sugar molecules disperse but do not change their chemical composition).

c) Burning wood is a chemical change because wood reacts with oxygen to produce new substances like ash, carbon dioxide, and water.

d) Cutting paper is a physical change (the paper is just in smaller pieces).

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Question 4: If a car travels at a constant speed of 60 km/h for 3 hours, how far has it traveled?

a) 20 km

b) 60 km

c) 180 km

d) 300 km

The correct answer is c) 180 km.

Step 1: Calculate distance.
Distance is calculated by multiplying speed by time.

$$\text{Distance} = \text{Speed} \times \text{Time}$$ $$\text{Distance} = 60\ \text{km/h} \times 3\ \text{h}$$ $$\text{Distance} = 180\ \text{km}$$

The car has traveled 180\ km.