Explanation

About 97% of the Earth's water is contained in the oceans, which is saltwater.

The remaining 3% is freshwater, but most of it is frozen in glaciers and polar ice caps.

Only about 0.3% of the Earth's water is freshwater that is readily available for human consumption, agriculture, and other uses.

Explanation

Mercury (Hg) is used in thermometers.

Because it expands and contracts consistently with temperature changes.

It providing accurate readings.

It also emits ultraviolet light in fluorescent tubes when electrically excited.

Explanation

The stratospheric ozone layer is Earth's “sunscreen”  protecting living things from too much ultraviolet radiation from the sun.

Oxygen layer in the atmosphere

Ozone protects us from the harmful ultraviolet radiation of the sun.

Ozone formula: O3

The ozone layer lies approximately 15-40 kilometers (10-25 miles) above the Earth's surface, in the stratosphere.

The ozone layer is depleting: Air pollution

ND17-7-2023

Explanation

Explanation

Explanation

The age of a tree is determined by counting its growth rings.

They are visible in the cross-section of the stem.

Each ring represents one year of growth.

Explanation

Platelets (a type of blood cell) and proteins in your plasma (the liquid part of the blood) work together to stop the bleeding by forming a clot over the injury. 

Vitamin K helps to make various proteins that are needed for blood clotting and the building of bones.

Explanation

HCl creates an acidic environment (pH 1.5 to 3.5) that activates the enzyme pepsin from its inactive form, pepsinogen.

Pepsin then breaks down proteins into smaller peptides, facilitating digestion.

Explanation

Priestly discover oxygen in 1776.

Oxygen makes up about 46-50% of the Earth's crust by weight, mainly in the form of oxides and silicates.

It is also a major component of water (H₂O).

It is abundant in the atmosphere as O₂.

Explanation

Biology

Life and living organisms, including their structure, function, growth, evolution, and interaction with their environment.

Geology
The Earth, its materials (rocks, minerals), structure, and the processes that shape it (earthquakes, volcanoes, plate tectonics).

Chemistry

Matter, its properties, how it interacts, combines, and changes (chemical reactions, molecular bonds, atomic structure).

Physics:

The fundamental forces and principles of the universe, such as energy, motion, force, and the nature of matter.