Chapter 1- Elements Flashcards
(17 cards)
Do Compounds conduct electricity?
No. Only when ionic compounds are molten are they able to conduct electricity
What is the meaning of a chain reaction?
A self-sustaining series of reactions in which the products of the reaction contribute directly to the next reaction.
How would you determine whether a given substance is a compound or mixture
Check if the melting point of the solid. If it has a fixed melting point, the sample is a compound. However, if the solid melts over a wide range of temperatures, it’s a mixture.
Perform chromatography. A single spot implies the sample is a pure compound. If it has more than 1 spot, it’s a mixture
What are the general properties of metals?
They are shiny, mostly solids, high B.P and M.P, ductile, malleable, sonorous, good electrical and heat conductors.
What are the general properties of metalloids?
They are shiny, solid, have high B.P and M.P, brittle and moderate electrical and heat conductors
What are the general properties of non-metals?
They are dull in colour, are gases, volatile liquids, or solids. They have low melting and boiling points other than carbon and silicon, brittle if solid and are poor heat and electrical conductors (other than carbon in the form of graphite and diamond. But diamond can’t conduct electricity.
What are the differences between a compound and a mixture?
A mixture can be separated by physical processes like magnetic separation, filtration or distillation. A compound can only be broken down into its elements or into simpler compounds by chemical processes, like thermal decomposition or electrolysis.
The chemical properties of a mixture are the same as those of the components of a mixture. The physical and chemical properties of a compound are different from those of its constituent elements.
NO chemical reaction takes place when a mixture is formed- usually little or no energy change. A chemical reaction takes place when a compound is formed- usually there’s an energy change, eg. the reactants get hot or cold.
The components of a mixture can be mixed in any proportion. the elements in a compound are always combined in a fixed proportion.
What types of mixtures are there?
Mixtures can be made out of:
- Two elements (Eg. H2 and Ne)
- Two compounds(Eg. H20 and C02)
- One element and one compound.(eg. H2 and NH3)
What’s a pure substance
It is made up of ONE SINGLE element or compound
Why is Crystallisation used to extract a pure solid from a solution?
Some substances decompose when heated strongly.
What can we do to test if a solution is saturated or not?
Dip a clean glass rod into the solution and remove it soon after that. There will be a small amount of solution on the rod. If small crystals form on the rod and the solution cools, the solution is saturated. We say the solution is at its saturation point or crystallisation point.
How do we separate a mixture of 2 solids?
Use a solvent in which only ONE solid is soluble.
How to separate 2 immiscible liquids, for example oil and water?
- Pour mixture into separating funnel
- Support funnel with retort stand
- Allow liquids to separate completely
- Open tap of funnel to allow bottom layer to drain into the beaker. Close the tap before the top layer of liquid runs out.
- Place another beaker below the funnel. Open the tap to allow a little of the top layer of liquid into the beaker. Dispose of the liquid collected.
What happens during fractional distillation?
The liquid which is more volatile reaches the upper part of the column and is distilled over first.
The vapours of liquids with higher boiling points condense along the fractionating column and fall back into the round-bottomed flask.
How to carry out Chromatography?
- Draw a line with a pencil at about 1cm from the bottom of a strip of filter paper or chromatography paper.
- Put a drop of green food colouring on the pencil line. Allow the drop to dry.
- Dip the paper into a glass tank containing the solvent. The solvent is soaked up by the paper and will dissolve the dyes.
- Leave the apparatus to stand for a while. The more soluble a dye is in the solvent, the further it will move up the paper.
What is a chromatography paper with the separated components called?
A Chromatogram
What’s a locating agent used for?
To make colourless substances visible. It reacts with the substances to form coloured spots
