Given the stoichiometric reaction, strong chemical bonds have been broken and reformed, and new chemical substances, carbon dioxide, and water, have been formed. Ergo, this is a chemical change. Is wood burning a physical or chemical change? Chemistry Matter Physical and Chemical Changes. Apr 22, Chemical change. Explanation: New substances are formed when wood burns. Explanation: Here we got combustion of wood, the which we may treat as cellulose, i. Ask yourself what you can measure for the quantitative observations.
For your observations and measurements, consider not only the physical candle, but also consider its influence on the air in the space surrounding it.
Now sketch a detailed drawing of the burning candle, an enlargement of the portion about a centimeter from the top of the candle to the topmost tip of the flame:. Now distinguish as many different aspects of the flame itself and label them in the drawing. When you have completed recording your observations and drawings, prepare to blow out the candle, and be ready to make further observations as you do this! Blow out the candle and record two qualitative and two quantitative observations of the candle immediately after it is extinguished:.
In a phase change from solid to liquid or from liquid to gas the particles of a substance in this case the molecules of wax will change the arrangement they have with each other. As a solid they will be closely packed together and unable to move freely. In the liquid they will be able to flow around each other but will still be close together, and as a gas they will fly freely apart but they will still be wax molecules and will have the same structure they had as molecules in the solid and the liquid phases:.
In the boxes below, use small, single shapes to represent entire wax molecules, and sketch their arrangement in the three physical phases:.
Based on your observations of the burning candle, did you find evidence for the change from the solid wax phase to the liquid wax phase? Interestingly, a candle releases energy through the same kind of reaction that your body uses to obtain energy. Hold your breath for a moment. What is your body craving? This is the same substance the candle needs to burn in a chemical change that we call combustion.
We are not aware of oxygen in the air because it is an odorless and colorless gas, and at the temperature of a burning candle, both the CO2 and the H2O are also gases that are invisible to us. We can see evidence of chemical change, however, if we restrict the amount of oxygen that is allowed to react with the wax. Relight the candle and lower the bottom of a small beaker or a clear watch glass into the flame so that the flame touches the surface of the glass.
Hold it there for a moment where it restricts some of the air flow to the flame and then remove it. Finally, let us consider the physical phase of the wax as it reacts with the oxygen to produce carbon dioxide and water. Prepare to observe carefully! Blow out the candle and very quickly bring a match close to the wick.
Try to notice exactly where the lit wooden splint is with respect to the wick when the candle reignites. Do this several times to see if you observe something interesting. Note any evidence you have observed that helps to determine the physical phase of the wax when it reacts with oxygen.
If you do not respond, everything you entered on this page will be lost and you will have to login again. Skip Navigation. Lab Investigation. Teacher's Overview Summary In this investigation, students are challenged to make careful observations about a burning candle to discover the chemical and physical changes that make it work. Objective Students will desribe their observations about a burning candle to discover the chemical and physical changes that make it work.
Safety Be sure to wear safety goggles while making close observations, tie your hair back if you have long hair, and always be aware of where the flame is with respect to your clothing—do not lean over the flame. Burning candles are open flames that can cause burns. Liquid wax is hot and can cause burns to the skin. Lab Tips Tea candles can be purchased in large quantities, as can tapered candles from hardware stores.
Student Investigation. Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:. Skip to main content. Introduction to Chemistry. Search for:. Physical and Chemical Changes to Matter. Learning Objective Identify the key features of physical and chemical changes. Key Points Physical changes only change the appearance of a substance, not its chemical composition. Chemical changes cause a substance to change into an entirely substance with a new chemical formula.
Show Sources Boundless vets and curates high-quality, openly licensed content from around the Internet. Licenses and Attributions.
0コメント