6th Grade 4.2- Physical And Chemical Changes

When plants undergo photosynthesis, they convert water and carbon dioxide into sugar and oxygen through a series of chemical reactions. This process involves the breaking and formation of chemical bonds, resulting in the production of new substances. Therefore, the occurrence described in the question is a chemical change, not a physical change.

When wood burns, it undergoes a chemical change. Burning wood involves a chemical reaction called combustion, where the wood reacts with oxygen in the air to produce heat, light, and various combustion byproducts such as carbon dioxide and water vapor. This chemical reaction results in a permanent change in the composition and properties of the wood, making it a clear example of a chemical change rather than a physical change.

When a watermelon is smashed into the ground, it undergoes a physical change. This is because the physical state or appearance of the watermelon changes, but its chemical composition remains the same. The smashing of the watermelon only alters its shape and texture, but the molecules and atoms that make up the watermelon are still the same. Therefore, it is considered a physical change rather than a chemical change.

When you eat food, your body undergoes a process called digestion, where the food is broken down into smaller molecules such as carbohydrates, proteins, and fats. These molecules are then further broken down through various chemical reactions in the body to release energy. This transformation of food into energy involves the rearrangement of atoms and the formation of new substances, indicating a chemical change.

When a popsicle melts, it undergoes a physical change. This is because the change in state from solid to liquid does not involve any chemical reactions or the formation of new substances. The molecules in the popsicle simply gain enough energy to break free from their fixed positions and move more freely, resulting in a change in physical form.

A chemical change refers to a process in which the original substances undergo a transformation and change into different substances with new chemical properties. This involves the breaking and forming of chemical bonds, resulting in a change in the composition and structure of the substances involved. Unlike physical changes, such as changes in state or shape, a chemical change is not reversible and often involves the release or absorption of energy.

The Grand Canyon is an example of a physical change because it is a result of natural processes of erosion and weathering over millions of years. These processes have physically altered the landscape, creating the deep canyon with its distinct layers and formations. No new substances are formed during this process, making it a physical change rather than a chemical change.

Physical change refers to any change in size, shape, or form of matter. Unlike chemical change, which involves a rearrangement of atoms and results in the formation of new substances, physical change does not alter the chemical composition of the matter. Examples of physical changes include melting, freezing, boiling, cutting, and crushing. In these processes, the substance may change its state or appearance, but its chemical identity remains the same. Therefore, physical change is the correct answer for the given question.

When iron and oxygen in the air react slowly, they undergo a chemical reaction known as oxidation. This reaction results in the formation of a reddish-brown compound called rust. Rust is a combination of iron oxide and usually forms on the surface of iron or steel objects when they are exposed to moisture and oxygen over time.

When leaves change color in the fall, it is an example of a chemical change. This is because the process of changing color involves the breakdown of chlorophyll, the pigment responsible for the green color in leaves, and the synthesis of other pigments such as carotenoids and anthocyanins. This chemical reaction alters the composition of the leaf, resulting in a different color. It is not a physical change because the molecular structure of the leaf is being altered, rather than just a change in its physical state or appearance.