Heating zinc oxide is physical changes because zinc oxide is a white powder the loss of oxygen makes it reversible chemical change so the oxidation takes place.

Thus, when zinc oxide is heated in air, there is a change in colour from white to yellow, and when we cool it, it reverts back. The zinc oxide heated will absorb blue light wavelength, and reflected light will turn yellow. The colour change occurs due to loss of oxygen.

Zinc Oxide is originally a white powder. When heated up, it turns yellow but does not decompose and when it is removed from the heat it gradually goes back to its original white color. If you heat it strongly enough to very high temperatures it will sublime without apparent decomposition.

When zinc oxide is heated strongly above 800∘C it turns yellow. After cooling down, the colour of zinc oxide changes back to white. Thus, it is a reversible process. The hot zinc oxide absorbs blue wavelength of light and thus, the reflected light is observed as yellow.

The temperature gradient effect is utilized in the co-precipitation method for ZnO synthesis which resulted in reduction of the average particle size (from 64 nm to 44 nm) with increase in reaction temperature. ZnO nano particles so obtained are spherical in shape.

yellow

In ZnO, Zn2+ ions occupy the interstitial sites and electrons are trapped in the interstitial sites for the neutralization. Zinc oxide is white in color but on heating it turns into yellow because on heating it loses oxygen reversibly at high temperature.

The colour of the lead oxide before heating is red/ orange while after heating its colour changes to yellow.

Zinc oxide is white in color but on heating, it turns into yellow because it loses oxygen reversibly at high temperatures.

Lead monoxide

Litharge is the key component in the manufacture of chrome-yellow and chrome-green pigments. It serves as an accelerator, toughener, and control ingredient in rubber production and as a catalyst in oil refining, where it breaks up some of the organic sulfur compounds found in petroleum.

Litharge, also called Lithargite, one of two mineral forms of lead(II) oxide (PbO).

Litharge, or alpha lead monoxide, is a red or reddish yellow solid, has a tetragonal crystal structure, and is the stable form at temperatures below 488° C (910° F). Massicot, or beta lead monoxide, is a yellow solid and has an orthorhombic crystal structure; it is the stable form above 488° C.

Litharge is prepared as the oxidized product of molten lead that has been stirred or atomized to incorporate air then cooled and ground to form the yellow powder. Massicot, another crystalline form of lead monoxide, occurs naturally but can also be made by heating lead carbonate to 300C.

Lead(II,IV) oxide, also called red lead or minium, is the inorganic compound with the formula. . A bright red or orange solid, it is used as pigment, in the manufacture of batteries, and rustproof primer paints.

Pb3O4

Minium, also known as red lead, is a bright orange red pigment that was widely used in the Middle Ages for the decoration of manuscripts and for painting.

Iron(III) oxide

Mixed oxide is a combination of two different oxides. For example: Fe3O4 is a mixed oxide of Fe2O3 and FeO. Similarly, Pb3O4 is a mixed oxide of 2PbO. Only oxygen can form mixed oxides, sulphur cannot form mixed sulphides, and similarly other elements of the group cannot form mixed oxides.

Lead oxide

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Nitrogen has an oxidation state of +3 in the oxide N₂O₃ (a dark blue liquid with acidic properties) and nitrous acid HNO₂.

+6