now as we know candle contains wax then when the candle melts it is an physical change but when the candle solidifies it is a chemical change.
When a candle burns, both physical & chemical changes occur.
Physical Changes in Burning Candle: On heating, candle wax melts and form liquid wax. It is a physical change. Since it again turns into solid wax on cooling. This is a reversible change.
Chemical Changes in Burning Candle: When you light the candle, the wax present near the wick will melt. Wick absorbs the liquid wax. The liquid wax vaporizes due the heat produced by the flame. This wax vapor near to flame burns and gives new substances like Carbon Dioxide, Carbon soot, water vapours, heat and light. This is an irreversible change.
Ans. It is a physical change because It doesn't show new properties.
Wildfires represent one of the most common disturbances in boreal regions, and have the potential to reduce C, N, and Hg stocks in soils while contributing to atmospheric emissions. Organic soil layers of the forest floor were sampled before and after the FROSTFIRE experimental burn in interior Alaska, and were analyzed for bulk density, major and trace elements, and organic compounds. Concentrations of carbon, nutrients, and several major and trace elements were significantly altered by the burn. Emissions of C, N, and Hg, estimated from chemical mass balance equations using Fe, Al, and Si as stable constituents, indicated that 500 to 900 g C and up to 0 to 4 × 10−4 g Hg/m2 were lost from the site. Calculations of nitrogen loss range from −4 to +6 g/m2 but were highly variable (standard deviation 19), with some samples showing increased N concentrations post‐burn potentially from canopy ash. Noncombustible major nutrients such as Ca and K also were inherited from canopy ash. Thermogravimetry indicates a loss of thermally labile C and increase of lignin‐like C in char and ash relative to unburned counterparts. Overall, atmospheric impacts of boreal fires include large emissions of C, N and Hg that vary greatly as a function of severe fire weather and its access to deep organic layers rich in C, N, and Hg. In terrestrial systems, burning rearranges the vertical distribution of nutrients in fuels and soils, the proximity of nutrients and permafrost to surface biota, and the chemical composition of soil including its nutrient and organic constituents, all of which impact C cycling.
Emissions and ash deposition from wildfires have important impacts on atmospheric and watershed chemistry [Liu et al., 2000; Van Wyk et al., 1992], forest biogeochemical cycling [Trabaud, 1994], and the types and rates of vegetative regrowth [Luc and Luc, 1998; Schimel and Granstrom, 1989]. Fires are particularly widespread and severe in boreal forests [Kasischke and Stocks, 2000] and can lead to major changes in the elemental composition of soils and vegetation. In particular, fires can lead to combustion losses of organic matter and nutrients, changes in the availability of plant nutrients, and mobilization of particulates into the atmosphere, soils, and streams.
forest fires occurs
due to pollutants
b) man made industries
follow me give me Star ⭐⭐⭐⭐⭐
A. Addition reaction
B. Decomposition reaction
C. Displacement reaction
D. Double displacement
Please solve it fast