Question

critical thinking
use this photo to answer the following question.
7 analyze as the bright sun shines upon the water, the water slowly disappears. the same sunlight gives energy to the surrounding plants to convert water and carbon dioxide into sugar and oxygen gas. which change is physical and which is chemical?
8 compare relate the statement \you cant get something for nothing\ to the law of conservation of mass.
9 infer sharpening a pencil leaves behind pencil shavings. is sharpening a pencil a physical change or a chemical change? explain.
lesson 3 physical and chemical changes

Explanation:

Question 7

Step1: Define physical and chemical change

Physical change is a change in state or form without changing chemical composition. Chemical change results in new substances with different chemical properties.

Step2: Analyze water - disappearance

Water disappearing due to sunlight is evaporation. It changes from liquid to gas state. No new substance is formed. So, it's a physical change.

Step3: Analyze plant - process

Plants converting water and carbon - dioxide into sugar and oxygen gas is photosynthesis. New substances (sugar and oxygen) are formed. So, it's a chemical change.

The law of conservation of mass states that mass is neither created nor destroyed in a chemical or physical process. The statement "You can't get something for nothing" implies that there is always an input or cost to get an output. In the context of the law of conservation of mass, matter (mass) must be present initially to be transformed or used in a process, and the total mass remains constant throughout. There is no creation of mass out of nothing.

Step1: Recall physical and chemical change definitions

Physical change is a change in form or state without altering chemical composition. Chemical change involves formation of new substances.

Step2: Analyze pencil - sharpening

Sharpening a pencil only changes its physical form. The pencil shavings are still made of the same graphite and wood material as the original pencil. No new chemical substances are formed.

Answer:

The disappearance of water is a physical change. The conversion of water and carbon - dioxide into sugar and oxygen by plants is a chemical change.

Question 8