Physical Changes: On heating, candle wax gets melted. Since it again turns into solid wax on cooling. So, the melting of wax and vapourisation of melted wax are physical changes. Chemical Changes : The wax near flame burns and gives new substances like carbon dioxide, carbon soot, water vapour, heat and light.

Burning of candle is actually chemical change. Wax is basically made up of hydrocarbons. When you light the wick, the wax near the wick melts and then goes up through the thread through capillary action. Then the liquid turns to hot gas where the hydrocarbons are broken down.

Melting of wax is physical change because only physical state is changing from solid to liquid but burning of wax is chemical change because in burning, wax reacts with oxygen present in surroundings and forms carbon di oxide and ash.

Answer: Baking a cake is a chemical change because the baking powder or soda whichever one undergoes a chemical reaction. Heat helps baking powder produce tiny bubbles of gas which makes the cake light and fluffy.

Many reactions can be created using common household items such as vinegar, food coloring, dish soap and salt. Some reactions are very messy and should be done outside if possible.

There’s no real chemical reaction here – as you say, it’s a physical process, which is why rubbing the soap helps – you’re applying shear to the structure and helping to separate the strands.

Baking soda, or sodium bicarbonate (NaHCO3), is a chemical that can undergo a decomposition reaction when heated. At temperatures above 176 degrees Fahrenheit (80 degrees Celsius), sodium bicarbonate starts to break down into three compounds, forming sodium carbonate (Na2CO3), water (H2O) and carbon dioxide (CO2).

Baking soda added to water raises the temperature slightly. Chemical reactions are either endothermic or exothermic. Left over heat will raise the temperature. Baking soda and water is exothermic and so the water gets a little warmer.

When baking soda is mixed with vinegar, something new is formed. The mixture quickly foams up with carbon dioxide gas. If enough vinegar is used, all of the baking soda can be made to react and disappear into the vinegar solution. Sodium bicarbonate and acetic acid reacts to carbon dioxide, water and sodium acetate.