Unit 2

What are the two main subatomic particles found in the atomic nucleus?

Protons and neutrons.

What are the major chemical elements found in living things? Name the most common one.

Oxygen, nitrogen, and carbon; most common is oxygen.

How do atoms combine with each other? What do they form?

Atoms combine through the interaction of valence electrons, forming molecules.

What type of chemical bonding involves the sharing of electrons? Provide an example.

Covalent bonding; an example is the bonds within a water molecule.

How does an atom differ from an ion?

Atoms are neutral with equal protons and electrons; ions have unequal numbers of protons and electrons.

What molecular structure does water have? Describe the bonds.

Water has covalent bonds between oxygen and hydrogen atoms within the molecule.

List one property of water and an example.

Water has high surface tension; for example, water striders can walk on water.

What is the pH scale used for?

The pH scale is used to measure the acidity or alkalinity of liquids.

What is the key difference between exothermic and endothermic reactions?

Exothermic reactions release energy (feel hot), while endothermic reactions absorb energy (feel cold).

What are enzymes and what role do they play in chemical reactions?

Enzymes are biological catalysts that speed up chemical reactions in the body.

Provide an example of an enzyme and its substrate reaction.

Lactase breaks down lactose into glucose and galactose.

What factors can impact enzyme activity?

Temperature and pH.