Chapter 11: Chemical Changes, Acids and Alkalis Flashcards
(25 cards)
What are the 2 types of changes?
Physical and Chemical changes.
What are the differences between physical and chemical changes?
- Physical changes are reversible, but chemical changes are irreversible.
- Physical changes are temporary, but chemical changes are permanent.
- Chemical changes form new substances, but physical changes do not form new substances.
Why is the total mass of products equal to the total mass of reactants, despite the fact that the products are chemically different from the reactants?
The total mass of products is equal to the total mass of reactant, because atoms are not created or destroyed. The products are chemically different from the reactants, because atoms are rearranged in a chemical reaction, forming new substances.
What are the four ways in which new substances can be formed due to chemical changes?
Heat, Light, Electricity and Mixing
What are exothermic and endothermic reactions?
A chemical reaction that releases heat is called an exothermic reaction. A chemical reaction that gains heat is called an endothermic reaction.
What is thermal decomposition? Is it an endothermic or exothermic reaction? Give an example of thermal decomposition, as well as the word equation for said example.
(ENDOTHERMIC REACTION) Thermal decomposition is the process by which a substance, when heated, is broken down into 2 or more simpler substances. An example is that sugar decomposes into carbon and water vapour through heating. Sugar ——> (heat) carbon + water vapour
What is combustion/burning? Is it an endothermic or exothermic reaction? Give an example of combustion/burning, as well as the word equation for said example.
(EXOTHERMIC) combustion is the process, by which a substance, when heated, combines with oxygen in the air to form new substances, giving out heat, and sometimes light. An example is when carbon combines with oxygen to form carbon. Dioxide through heating. carbon + oxygen ——>(heat) carbon dioxide
What is oxidation? Is it an endothermic or exothermic reaction? Give an example of oxidation, as well as the word equation for said example.
(EXOTHERMIC) The addition of oxygen to a substance to form a new substance is called oxidation, occurring when metals or nonmetals react with oxygen in the air. An example is when iron reacts with oxygen to form iron(III) oxide, also known as rust. Iron + oxygen ——> iron(III) oxide. Another example is cellular respiration, when living cells of plants and animals take in oxygen to release the energy stored in glucose. Glucose + oxygen——> carbon dioxide + water (Neither require heat to occur!!!)
What is photosynthesis? What is the word equation for it?
Light energy is absorbed by green plants to make food (glucose). carbon dioxide + water ——> (light) glucose + oxygen
What is photography? What is the word equation for it?
when films are developed into negatives, light decomposes the silver bromide coating on photographic films into silver, which produces the dark areas on the film, according to the shape of the image formed. Silver bromide ——>(light) Silver + Bromine
What is electrolysis? What are some examples of electrolysis?
electrolysis is the chemical decomposition of substances with the passage of an electric current. some examples of electrolysis is separating water into its components, oxygen and hydrogen, and electroplating, a process, in which a substance is coated with a metal with the passage of a electric current.
What is the general equation for mixing an acid and a metal?
Acid + metal -> salt + hydrogen gas
What is the general equation for mixing an acid and a carbonate?
Acid + carbonate -> salt + water + carbon dioxide
What is the general equation for mixing an acid and an alkali?
Acid + alkali -> salt + water (this is called neutralisation, and its also compulsory to know this)
how do you know if there is gas being produced in a reaction?
There will be effervescence.
How do you test if hydrogen gas is produced in a reaction?
Insert a lighted splints into the test gas, and if there is hydrogen gas, the lighted splint will extinguish with a pop sound.
how do you test if carbon dioxide is produced in a reaction?
bubble the test gas into limewater, and if there is carbon dioxide, white precipitate will be formed in the limewater.
How do you test if oxygen is produced in a reaction?
Insert a glowing splint into the test gas, and if there is oxygen, the splint will rekindle.
How do you know whether a solution is acidic, alkaline, or neutral using the pH scale?
if a solution’s pH value is less than seven (orange or red in colour), it is acidic. If a solution’s pH value is more than seven (blue or violet in colour), the solution is alkaline. if a solution’s pH value is seven (green in colour), the solution is neutral.
What are the physical properties of acids?
- Acids have a sour taste.
- Acids turn blue litmus paper red.
What are the chemical properties of acids?
Acids react with other substances to form new substances during chemical changes. For example, dilute acid reacts with metal to produce salt and hydrogen gas. Dilute acid reacts with carbonates to produce salt, water and carbon dioxide gas. Dilute acid reacts with alkalis to produce salt and water, also known as neutralisation.
What are the physical properties of alkali?
- Alkalis have a bitter taste.
- Alkalis turn red litmus paper blue.
What are the chemical properties of alkalis?
Alkalis react with other substances to form new substances during chemical changes. for example, dilute acid reacts with alkalis to produce salt and water.
How would you identify an unknown solution to be neutral pH, using litmus paper?
Dip blue litmus paper and red litmus paper into the solution. Blue litmus paper would remain blue and red litmus paper would remain red.
