Question

1. matter can undergo physical or chemical changes. which of these are examples of physical changes? burning paper breaking an egg spoiled milk freezing a popsicle silver tarnishing

Explanation:

To determine physical changes, we recall that a physical change is a change in matter that does not change its chemical identity.

• Burning paper: Involves combustion, a chemical reaction (new substances like ash, CO₂ are formed) → chemical change.
• Breaking an egg: Breaking the shell is a physical change (no new substance, just change in shape/state of the shell; the egg inside may start to change chemically, but the breaking itself is physical). Wait, actually, breaking an egg (like cracking the shell) is physical, but if we consider the yolk/white mixing, but the option is "Breaking an egg" (probably the shell). However, let's re - evaluate:
• Freezing a popsicle: Liquid to solid (water in popsicle freezes), no new substance, just change in state → physical change.
• Spoiled milk: Bacteria act, chemical composition changes (sour taste, new compounds) → chemical change.
• Silver tarnishing: Silver reacts with sulfur in air to form silver sulfide (new substance) → chemical change.

Wait, the question is "Which of these are examples of physical changes?". So we need to identify which processes don't form new substances.

• Freezing a popsicle: Phase change (liquid to solid), no new substance.
• Breaking an egg: If we consider the act of breaking the shell (mechanical break), no new substance. But maybe the question considers "breaking an egg" as just the shell break. However, let's check again:

Physical change criteria: no new chemical substance, change in state (solid/liquid/gas), shape, size, etc.

• Freezing a popsicle: Liquid (popsicle mix) to solid (frozen popsicle) → physical (phase change).
• Breaking an egg: The shell is broken, the egg's physical form is changed, but no new substance from the breaking (the egg's contents may start to change, but the breaking is physical). Wait, but maybe the options are:

Wait the options are: Burning paper, Breaking an egg, Freezing a popsicle, Spoiled milk, Silver tarnishing.

So correct physical changes: Freezing a popsicle (phase change, no new substance) and Breaking an egg (mechanical break, no new substance). Wait, but let's confirm:

• Burning paper: Chemical (combustion, CO₂, ash).
• Spoiled milk: Chemical (bacterial action, new compounds).
• Silver tarnishing: Chemical (Ag + S → Ag₂S).
• Freezing a popsicle: Physical (H₂O(l) → H₂O(s), no new substance).
• Breaking an egg: Physical (change in shape of the egg shell, no new substance formed from the breaking itself).

But maybe the question has these as options, and we need to select the physical changes. So the physical changes are Freezing a popsicle and Breaking an egg. But let's check the original problem's options (the checkboxes). The options are:

• Burning paper (checkbox)
• Breaking an egg (checkbox)
• Freezing a popsicle (checkbox, currently selected)
• Spoiled milk (checkbox)
• Silver tarnishing (checkbox)

So to answer, we identify physical changes:

1. Freezing a popsicle: Phase change (liquid to solid), no new chemical substance.
2. Breaking an egg: Mechanical breakage, no new chemical substance (the egg's contents may undergo chemical change later, but the breaking is physical).

Burning paper (chemical, combustion), Spoiled milk (chemical, decomposition), Silver tarnishing (chemical, oxidation) are chemical changes.

Answer:

The examples of physical changes are:

• Breaking an egg (checkbox should be selected)
• Freezing a popsicle (checkbox is already selected)