This worksheet challenges students to distinguish between matter made of molecules and subatomic particles by marking items like water and DNA.

Problem Analysis:

The task asks us to identify which items on the list are made up of one or more molecules. To solve this, we need to understand what constitutes a molecule and how it relates to the items listed.

#### Key Concepts:
1. Molecule: A molecule is a group of two or more atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction.
2. Atoms: Atoms are the basic building blocks of matter and are not considered molecules unless they are bonded with other atoms.
3. Substances vs. Objects: Some items on the list are substances (e.g., water, sugar), while others are objects or living entities (e.g., bread, worm). Substances are typically composed of molecules, whereas objects may be composed of cells, tissues, or other complex structures.

Solution Approach:

We will go through each item on the list and determine whether it is made up of molecules based on the following reasoning:
- Substances: If an item is a substance (like water, sugar, DNA), it is made up of molecules.
- Living Entities: Living entities (like bread, worms, bacteria) are composed of cells, and cells are made up of molecules.
- Non-Molecular Items: Items like protons, electrons, and atomic nuclei are not molecules; they are subatomic particles or components of atoms.

Item-by-Item Analysis:

#### Left Column:
- Bread: Bread is a food item made from flour, water, yeast, etc., all of which are composed of molecules. X
- Protons: Protons are subatomic particles and are not molecules. No X
- Water: Water is a substance composed of H₂O molecules. X
- Atomic Nucleus: The atomic nucleus is a structure within an atom and is not a molecule. No X
- Brain Cell: Brain cells are biological cells, and cells are composed of molecules. X
- Milk: Milk is a liquid composed of various molecules, including proteins, fats, and sugars. X
- Egg: An egg is a biological structure composed of cells and molecules. X
- Atom: An atom is not a molecule unless it is bonded with other atoms. No X
- Seed: Seeds are biological structures composed of cells and molecules. X
- Bacteria: Bacteria are single-celled organisms composed of molecules. X
- Skin: Skin is a tissue composed of cells, which are made up of molecules. X

#### Right Column:
- DNA: DNA is a large molecule composed of nucleotides. X
- Cell Membrane: The cell membrane is a biological structure composed of molecules (e.g., phospholipids, proteins). X
- Cloud: Clouds are composed of water droplets or ice crystals, both of which are molecules. X
- Oil: Oil is a substance composed of molecules. X
- Worm: Worms are living organisms composed of cells and molecules. X
- Protein: Proteins are large molecules. X
- Sugar: Sugar is a substance composed of molecules (e.g., sucrose, glucose). X
- Flower: Flowers are biological structures composed of cells and molecules. X
- Chromosome: Chromosomes are structures within cells composed of DNA and proteins, both of which are molecules. X
- Blood: Blood is a fluid composed of cells and molecules. X
- Leaf: Leaves are biological structures composed of cells and molecules. X
- Air: Air is a mixture of gases (e.g., oxygen, nitrogen), which are composed of molecules. X
- Mushroom: Mushrooms are fungi composed of cells and molecules. X
- Electrons: Electrons are subatomic particles and are not molecules. No X
- Cell Nucleus: The cell nucleus is a structure within a cell composed of molecules. X
- Fruit: Fruits are biological structures composed of cells and molecules. X

Final Answer:

Marking the items with an "X" where applicable:

```
X bread X DNA
protons X cell membrane
X water X cloud
atomic nucleus X oil
X brain cell X worm
X milk X protein
X egg X sugar
atom X flower
X seed X chromosome X blood
X bacteria X leaf X air X mushroom
X skin X electrons X cell nucleus X fruit
```

Explanation of Thinking:

The "rule" used to decide if something was made of molecules was to consider whether the item is:
1. A substance (e.g., water, sugar, DNA), which is inherently composed of molecules.
2. A living entity (e.g., bread, worm, bacteria), which is composed of cells, and cells are made up of molecules.
3. A non-molecular item (e.g., protons, electrons, atomic nuclei), which are not molecules but rather subatomic particles or components of atoms.

By applying this reasoning, we can accurately determine which items are made up of molecules.

Final Boxed Answer:

\[
\boxed{
\text{X bread, X water, X brain cell, X milk, X egg, X seed, X bacteria, X skin, X DNA, X cell membrane, X cloud, X oil, X worm, X protein, X sugar, X flower, X chromosome, X blood, X leaf, X air, X mushroom, X cell nucleus, X fruit}
}
\]