Question

identify the physical (p) and chemical (c) changes around us.
you are making pancakes. first, you mix together flour, sugar and baking soda (1) ____ . in a separate bowl, you melt some butter (2) __ and then add eggs and milk and stir (3) __ . next, you combine the two mixtures and stir some more. you see little bubbles start to rise in the batter (4) ____ .
now it is time to cook! you put scoops of pancake batter on a hot pan with some melted butter. the scoops of batter start to sizzle and more little bubbles appear(5) ____ ! once there are no more new bubbles you flip over the pancake, and cook until the other side is nice and brown (6) ____ .
finally, you pour some syrup over the top and cut a big bite (7) ______ . delicious!

Explanation:

To determine if a change is physical (P) or chemical (C), we use the definitions: a physical change is a change in appearance or state without forming new substances, while a chemical change involves the formation of new substances (often with gas production, color change, heat change, etc.).

Step 1: Analyze "mix together flour, sugar and baking soda" (1)

Mixing these dry ingredients just combines them physically; no new substance is formed. So this is a physical change (P).

Step 2: Analyze "melt some butter" (2)

Melting butter changes it from solid to liquid, which is a change in state (from solid to liquid) without forming a new substance. This is a physical change (P).

Step 3: Analyze "add eggs and milk and stir" (3)

Adding and stirring these liquids with other ingredients is just mixing; no new substance is formed. This is a physical change (P).

Step 4: Analyze "little bubbles start to rise in the batter" (4)

The bubbles here are likely from baking soda reacting (but wait, at this stage, before cooking, maybe it's just mixing? Wait, no—when you mix baking soda with liquid (from eggs and milk), a reaction starts? Wait, no, in the batter before cooking, maybe the initial mixing of dry and wet: but actually, when baking soda (a base) reacts with an acid (from milk, maybe eggs), it produces CO₂ gas. Wait, but in step 4, when you combine the two mixtures (dry and wet), the baking soda reacts with acids in the wet ingredients to produce CO₂ bubbles. So this is a chemical change (C) because a new substance (CO₂ gas) is formed.

Step 5: Analyze "more little bubbles appear" (5) when cooking

When cooking the batter, the heat causes the baking soda reaction to speed up, and also the proteins in the eggs and flour are denaturing, and the batter is undergoing chemical changes (like Maillard reaction for browning, and the baking soda reaction producing more gas). The bubbles here are from chemical reactions (production of CO₂ and maybe water vapor, but mainly CO₂ from baking soda reaction and also the cooking process causing chemical changes). So this is a chemical change (C).

Step 6: Analyze "cook until the other side is nice and brown" (6)

Cooking (especially browning) involves the Maillard reaction, which is a chemical reaction between amino acids and reducing sugars, forming new brown-colored compounds. Also, the batter is being cooked, so new substances are formed (the cooked pancake is different from the batter). This is a chemical change (C).

Step 7: Analyze "cut a big bite" (7)

Cutting the pancake just changes its shape; no new substance is formed. This is a physical change (P).

Answer:

s:
(1) $\boldsymbol{P}$
(2) $\boldsymbol{P}$
(3) $\boldsymbol{P}$
(4) $\boldsymbol{C}$
(5) $\boldsymbol{C}$
(6) $\boldsymbol{C}$
(7) $\boldsymbol{P}$