Question

referring to the figures below, answer question 7 and question 8
a. molecular diagram → molecular diagram
b. molecular diagram → molecular diagram
c. molecular diagram → molecular diagram
d. molecular diagram → molecular diagram

1. which of the following figures represent a chemical change?

a. figure a
b. figure b
c. figure c
d. figure d

1. statement: \figure a represents a physical change.\ - is the statement true? why?

a. true. there are same number of particles before and after the change in figure a.
b. true. the composition and identity of particles are the same before and after the change in figure a.
c. false. figure a represents a chemical change because it contains different atoms before and after the change.
d. false. figure a represents a chemical change because its particles got closer after the change.

1. which figure correctly represents \2h₂o\?

a. molecular diagram
b. molecular diagram
c. molecular diagram
d. molecular diagram

Explanation:

Step1: Define chemical change

A chemical change forms new substances (particles with different compositions).

Step2: Analyze Figure A

Left: mixed particles (e.g., 1 yellow+1 black, 2 blacks, 1 yellow+1 black). Right: new particles (2 yellows+2 blacks). New substances form → chemical change.

Step3: Analyze Figure B

Left: identical particles (1 yellow+1 black). Right: separate yellow/black particles. No new substances → physical change.

Step4: Analyze Figure C

Left: large dark particles. Right: smaller dark particles. Same substance (dark), just broken → physical change.

Step5: Analyze Figure D

Left/right: same dark particles. No change → physical.

Step1: Define physical change

Physical change keeps particle composition/identity unchanged.

Step2: Evaluate Figure A

Left: mixed particles (e.g., 1 yellow+1 black). Right: new particles (2 yellows+2 blacks). Composition changes → chemical change, so statement is false.

Step3: Check options

Option c says "False. Figure A represents a chemical change because it contains different particles before and after the change." (Note: "atoms" likely typo for "particles"—key is new particles = chemical change.)

Step1: Interpret "2H₂O"

"2" = 2 molecules; H₂O = 1 O bonded to 2 Hs per molecule.

Step2: Analyze options

• A: Separate H₂ and O₂ → not H₂O.
• B: H₂ and O₂ mixed → not H₂O.
• C: 2 H₂O molecules (each H-O-H) → matches.
• D: Separate H and O atoms → not H₂O.

Answer:

a. Figure A