LONG ANSWER QUESTIONS

Q.1 Chalk, iron nail, wood, aluminium, candle, and cotton usually look different from each other. Give some properties by which we can prove that these materials are different.

Ans. here are revised properties that differentiate the materials:
Chalk – Soft, powdery, non-metallic
Iron nail – Hard, metallic, magnetic
Wood – Fibrous, non-metallic, combustible
Aluminium – Lightweight, metallic, non-magnetic
Candle – Waxy, combustible, non-metallic
Cotton – Soft, fibrous, non-metallic

Q.2 Why do you think oxygen dissolved in water is important for the survival of aquatic animals and plants?

Ans. Oxygen dissolved in water is crucial for the survival of aquatic animals and plants because it is essential for respiration. Aquatic organisms breathe oxygen dissolved in water through their gills or surface tissues. Without dissolved oxygen, aquatic life cannot respire effectively, leading to suffocation and potential death.

Q.3 Differentiate among opaque, translucent and transparent materials, giving one example of each.

Ans. Opaque materials do not allow light to pass through, like wood. Translucent materials allow some light to pass through but not clear images, like frosted glass. Transparent materials allow light to pass through clearly, like glass.

Q.4 Sugar, salt, mustard oil, sand, sawdust, honey, chalk powder, petals of flower, soil, copper sulphate crystals, glucose, wheat flour are some substances given to Paheli. She wants to know whether these substances are soluble in water or not. Help her in identifying soluble and insoluble substances in water.

Ans. Paheli can conduct a simple experiment to determine solubility. Substances like sugar, salt, mustard oil, honey, chalk powder, glucose, and copper sulphate crystals are soluble in water. Insoluble substances include sand, sawdust, petals of flower, soil, and wheat flour, which do not dissolve in water.