Q1: What are the main characteristics of an element?
A1: An element has the following characteristics:
- It is a pure substance.
- It has a fixed composition.
- It has a fixed set of properties.
- It cannot be broken down into simpler substances by chemical means.
Q2: What is the difference between a mixture and a compound?
A2: A mixture is a physical combination of two or more substances, whereas a compound is a chemical combination of two or more elements.
Q3: What is the law of conservation of mass?
A3: The law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction.
Q4: What is the difference between an acid and a base?
A4: An acid is a substance that donates H+ ions, whereas a base is a substance that accepts H+ ions.
Q5: What is the pH scale?
A5: The pH scale is a measure of the concentration of hydrogen ions in a solution, ranging from 0 to 14.
Q6: What is the difference between a physical change and a chemical change?
A6: A physical change involves a change in state or properties of a substance without changing its chemical composition, whereas a chemical change involves a change in the chemical composition of a substance.
Q7: What is a chemical reaction?
A7: A chemical reaction is a process in which one or more substances are converted into new substances.
Q8: What is the difference between a combination reaction and a decomposition reaction?
A8: A combination reaction involves the combination of two or more substances to form a new substance, whereas a decomposition reaction involves the breakdown of a single substance into two or more simpler substances.
Q9: What is the law of definite proportions?
A9: The law of definite proportions states that a chemical compound always contains its component elements in a fixed ratio by mass.
Q10: What is the difference between a metal and a non-metal?
A10: A metal is an element that is typically shiny, malleable, and good conductor of electricity, whereas a non-metal is an element that is typically dull, brittle, and poor conductor of electricity.
