Explanation

The stratosphere is the second layer of Earth's atmosphere as you go upwards, lying above the troposphere and below the mesosphere.

The layers of the Earth's atmosphere, in order from the surface, are:

1. Troposphere (up to about 12 km/7.5 miles)
2. Stratosphere (up to about 50 km/31 miles)
3. Mesosphere (up to about 85 km/53 miles)
4. Thermosphere (up to about 600 km/373 miles)

Explanation

• Atoms of the same element with different numbers of neutrons are called isotopes.
• Atoms of the same element have the same number of protons and electrons but different numbers of neutrons.

Explanation

Citric acid occurs naturally in:

• Lemons,
• Limes,
• Pineapples,
• Grapefruits,
• Berries (not blueberries),
• Tomatoes,
• Broccoli,
• Carrots,
• and some varieties of Peppers.

Explanation

Oxyacetylene welding, commonly referred to as gas welding,

is a process which relies on combustion of oxygen and acetylene

Explanation

The kinetic molecular theory states that gases are made up of small particles called molecules.

These molecules are in constant random motion and collide with each other and the container walls.

Explanation

John Dalton proposed the Atomic Theory in the early 1800s, stating that all elements are made of indivisible atoms.

He described atoms as indestructible and identical for each element, laying the foundation of modern chemistry.

Explanation

Explanation

Pyridine has a lone pair on nitrogen that is not involved in resonance, making it readily available for donation.

In aniline and phenol, lone pairs are delocalized into the aromatic ring, reducing basicity.

Explanation

• Carbon dating is used to estimate the age of fossils.
• Those that are less than 60,000 years old.
• It is composed of organic materials like wood or leather.

Explanation

The chemical name of "chalk" is calcium carbonate.

It is commonly used in classrooms and as a dietary supplement due to its high calcium content.