⚛️ Science Explorers Quiz (Grade 8) 🌿 [New]

⚛️ Science Explorers Quiz (Grade 8) 🌿

Dive into the world of science with these fundamental questions. Think carefully and discover the answers!

Question 1: Density (Physics) ⚖️

An object has a mass of 150 grams and a volume of 50 cubic centimeters (\(\text{cm}^3\)). Calculate its density. Based on your answer, will it sink or float in water? (The density of water is 1 g/cm³).

✅ Solution

First, we calculate the density using the formula:

$$ Density = \frac{Mass}{Volume} $$

We are given:

• Mass = 150 g
• Volume = 50 cm³

Substitute the values into the formula:

$$ Density = \frac{150 \text{ g}}{50 \text{ cm}^3} = 3 \text{ g/cm}^3 $$

The density of the object is 3 g/cm³.

Next, we compare the object's density to the density of water (1 g/cm³). Since the object's density (3 g/cm³) is greater than the density of water, the object will sink. 💧

Question 2: Atomic Structure (Chemistry) ⚛️

A neutral atom of Sodium (Na) has an atomic number of 11 and a mass number of 23. Determine the number of protons, neutrons, and electrons in this atom.

✅ Solution

Here are the key principles for determining the subatomic particles:

• Atomic Number = Number of Protons
• Mass Number = (Number of Protons) + (Number of Neutrons)
• In a neutral atom, the Number of Electrons = Number of Protons

Given for Sodium (Na):

• Atomic Number = 11
• Mass Number = 23

1. Protons: The number of protons is equal to the atomic number.

Number of Protons = 11.

2. Electrons: Since the atom is neutral, the number of electrons is equal to the number of protons.

Number of Electrons = 11.

3. Neutrons: We can find the number of neutrons by rearranging the mass number formula: Neutrons = Mass Number - Protons.

Number of Neutrons = 23 - 11 = 12.

Question 3: Plant vs. Animal Cells (Biology) 🧬

Describe two key differences between a typical plant cell and a typical animal cell.

✅ Solution

While plant and animal cells share many organelles (like the nucleus and mitochondria), there are several distinct differences. Here are three common ones:

1. Cell Wall: Plant cells have a rigid cell wall made of cellulose outside the cell membrane. This provides structural support. Animal cells do not have a cell wall.
2. Chloroplasts: Plant cells contain chloroplasts, which are the sites of photosynthesis. This is where they make their own food. Animal cells do not have chloroplasts because animals get energy by eating other organisms.
3. Vacuole: Plant cells typically have one large, central vacuole that stores water and helps maintain turgor pressure. Animal cells may have several small, temporary vacuoles, if any.

Answering with any two of the above would be correct. 🌿🐒

Question 4: The Water Cycle (Earth Science) 🌍

Name and briefly describe the three main stages of the Earth's water cycle.

✅ Solution

The water cycle describes the continuous movement of water on, above, and below the surface of the Earth. The three main stages are:

• 1. Evaporation ☀️: This is the process where liquid water from oceans, lakes, and rivers heats up from the sun's energy and turns into a gas called water vapor, rising into the atmosphere.
• 2. Condensation ☁️: As the water vapor rises, it cools down and changes back into tiny liquid water droplets, forming clouds.
• 3. Precipitation 🌧️: When the water droplets in the clouds become too heavy, they fall back to Earth in the form of rain, snow, sleet, or hail.

This cycle then repeats, making it a continuous process vital for life on Earth.

Excellent work! Curiosity is the engine of achievement. Keep exploring! 🚀