1. What are the four indicators that allow someone to know that a chemical react
ID: 715640 • Letter: 1
Question
1. What are the four indicators that allow someone to know that a chemical reaction has taken place? 2. What will you be looking for to know if a gas has been produced in a chemical reaction? How will you know a change in temperature happens? Briefly define: 3. 4. The term precipitate. The change that occurred was physical and not chemical. Determine whether each of the following observations is evidence of a physical or chemical change. Briefly explain. 5. On a hot day, drops of water collect on the outside of a glass holding ice tea. Clear, colorless lemon juice is added to a glass of iced tea. The tea color changes from brown to yellow brown. Water is added to iced tea. The tea color lightens.Explanation / Answer
Q1. The four indicators are :
Q2. Gas production on chemical reaction generally forms bubbles in liquid medium. These bubbles are formed because gas rises from bottom to surface in the form of bubbles. Hence we have to look for bubbles.
Q3. If the temperature change is positive, that is, temperature after reaction is higher then reaction vessel (like test tube , beaker) will be hot or warm to touch and if the temperature change is negative, that is, temperature after reaction is lower then reaction vessel will be cold to touch.
Q4. Precipitate : it is a solid substance (generally granular or crystalline) which is obtained as a reaction between two or more chemical species.
Physical change not chemical : This type of change does not involve breaking or forming of new bonds but rather change in physical form of substance : Example : freezing of water
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