chemistry Flashcards
Q: Define burning or combustion.
A: Burning is a chemical reaction in which a substance combines with oxygen.
Q: What is the substance that reacts with oxygen in burning called, and give examples?
A: It is called fuel. Examples include charcoal, wood, coal, natural gas, and oil.
Q: What happens when fuel burns?
A: The chemical energy in the fuel is converted into thermal, light, and sound energy, which dissipate into the surroundings.
Q: What are the components of the fire triangle?
A: Heat, oxygen, and fuel.
A: Heat, oxygen, and fuel.
Q: What is an exothermic reaction, and how does energy flow in it?
A: An exothermic reaction is a chemical reaction in which thermal energy is released from the system to the surroundings (chemical energy to thermal energy).
Q: Provide an example of an exothermic reaction.
A: The reaction in a self-heating can where calcium oxide reacts with water.
Q: Provide examples of endothermic processes.
A: Melting ice and dissolving potassium chloride in water.
Q: What is an oxidation reaction?
A: It is a reaction in which a substance combines with oxygen.
Q: Why is melting ice considered an endothermic process?
A: Thermal energy is absorbed from the surroundings as solid ice changes to liquid water.
Q: What happens to the particles in ice during melting?
A: Ice particles, initially arranged in fixed rows, absorb thermal energy, vibrate more vigorously, and eventually overcome the strong forces holding them in place, allowing them to move freely as a liquid.
Q: How do self-heating cans work?
A: A self-heating can has a compartment with calcium oxide and water. Pressing a button breaks the foil seal, mixing the substances, which react and release heat.
Q: Write the reaction involved in self-heating cans.
A: Calcium oxide + water → calcium hydroxide.
Q: What are the benefits of self-heating cans?
A: They are useful in remote areas or emergencies, portable, easy to use, and heat up contents quickly within minutes.
Q: What are the disadvantages of self-heating cans?
A: They are expensive to produce because the compartments must be sealed from one another and from the food so that it does not become contaminated. , not reusable, may heat unevenly, can break and become hazardous, and the temperature is not controllable.
Q: How do ice packs work, and what makes them endothermic?
A: Ice packs contain compartments with ammonium nitrate and water. When the compartments are broken, the substances mix, and the reaction absorbs heat, causing the pack to cool
Q: Why is this process not considered a reaction?
A: No new substance is formed; it’s simply a physical process where heat is absorbed.
A: No new substance is formed; it’s simply a physical process where heat is absorbed.
Q: What are the benefits of ice packs?
A: They can be used without a fridge or freezer, providing convenient cooling for injuries.
Q: What is the general equation for a metal reacting with oxygen
A: Metal + oxygen → metal oxide.
Q: Why don’t metals like gold and silver react with oxygen?
A: They are unreactive and considered inert.
Q: What is rusting, and which substance is formed?
A: Rusting is the reaction of iron with oxygen in the presence of water, forming iron oxide.
Q: Write the chemical equation for rusting.
A: Iron + oxygen → iron oxide.
Q: What conditions are required for rusting?
A: Both water and oxygen must be present.
Q: Where does iron rust the most and the least?
A: Iron rusts the most in water and air and the least in plain dry air.
Q: How can rusting be prevented?
A: By painting iron to block oxygen or galvanizing it with a protective layer of zinc.
A: By painting iron to block oxygen or galvanizing it with a protective layer of zinc.
