3. Chemical Changes Flashcards
What are the properties of metals that make them useful materials?
Metals are good conductors of heat and electricity, and their layers of atoms can slide over each other, allowing them to be bent or hammered into shape.
What is an alloy?
An alloy is a mixture of at least two elements, one of which is a metal, often having different properties from the pure metals.
Why is copper useful for electrical wiring and plumbing?
Copper is a good conductor of heat and electricity, can be bent but is hard enough to make pipes or tanks, and does not react with water.
What is the reactivity series?
It is an arrangement of metals in order of their reactivity from their reactions with water and dilute acids.
Describe a displacement reaction in terms of oxidation and reduction.
In a displacement reaction, a more reactive metal displaces a less reactive metal from its compound. Oxidation is the loss of electrons, and reduction is the gain of electrons.
How are unreactive metals like gold found in nature?
Unreactive metals are found in the Earth as the metal itself.
How are metals less reactive than carbon extracted from their oxides?
Metals less reactive than carbon are extracted by reduction with carbon, e.g., iron is reduced from iron oxide in a blast furnace.
How are metals more reactive than carbon, like aluminum, extracted?
Metals more reactive than carbon are extracted by electrolysis of molten compounds, which requires large amounts of energy.
What are phytomining and bioleaching?
Phytomining uses plants to absorb metal compounds; plants are then burned to produce ash containing metal compounds.
Bioleaching uses bacteria to produce solutions containing metal compounds.
How is copper obtained from copper salts solutions?
Copper can be obtained by electrolysis or by displacement using scrap iron.
Why should we recycle metals?
Recycling metals conserves limited resources, saves energy, and reduces environmental impact.
What happens when metal carbonates decompose on heating?
Metal carbonates decompose to produce carbon dioxide and a metal oxide.
What is produced when metal carbonates react with acids?
Metal carbonates react with acids to produce carbon dioxide, a salt, and water.
What happens to ions in an ionic substance when it is melted or dissolved in water?
The ions are free to move within the liquid or solution.
What is electrolysis?
Electrolysis is the process of using an electric current to break down an ionic substance into elements. The substance broken down is called the electrolyte.
During electrolysis, where do positively and negatively charged ions move?
Positively charged ions move to the cathode (negative electrode), and negatively charged ions move to the anode (positive electrode).
How can oxidation and reduction be defined?
Oxidation is the loss of electrons, and reduction is the gain of electrons.
What occurs at the cathode and anode during electrolysis?
At the cathode, positively charged ions gain electrons. At the anode, negatively charged ions lose electrons.
What is a half equation for a reaction at an electrode?
A half equation represents the reaction at an electrode, e.g.,
2πΆπββπΆπ2 + 2πβ
.
How do products form at the cathode and anode if there is a mixture of ions?
At the cathode, the products depend on the reactivity of the elements involved. At the anode, the products depend on the relative concentrations of the ions present.
What is electroplating and why is it used?
Electroplating involves using electrolysis to coat an object with a thin layer of metal for appearance, durability, or corrosion prevention.
How is aluminum manufactured by electrolysis?
Aluminum is produced by the electrolysis of a molten mixture of aluminum oxide and cryolite, forming aluminum at the negative electrode and oxygen at the positive electrode.
What is the role of cryolite in the extraction of aluminum?
Cryolite lowers the melting point of aluminum oxide, reducing the energy required for the process.
What products are formed during the electrolysis of sodium chloride solution?
Electrolysis of sodium chloride solution produces hydrogen, chlorine, and sodium hydroxide, which are important for various industrial applications.
