Chemistry Flashcards
Nucleus
The positively charged center of the atom consisting of protons and neutrons. Contains most of the atom’s mass. It is the control centre of the cell.
Electron
A particle that has a negative charge of electricity and travels around the nucleus of an atom.
Neutron
Have approximately the same mass as protons. They have no charge but contribute to the mass of the atom. 1800x heavier than electrons
Atom
The smallest part that a substance can be broken down into ‘naturally’.
Nucleus size
6 micrometers (µm)
Proton relative mass
1
Electron relative mass
0.0005
Neutron relative mass
1
How does the charge of subatomic particles result in an atom being neutral in charge.
All atoms have the same number of electrons as protons, so the positive and negative charges “cancel out”, making atoms electrically neutral.
Elements
The building blocks of all substances. Made up of atoms with the same number of protons in the nucleus
- same chemical properties
- proton number determines the element
Molecule
Two or more atoms chemically joined together. The number varies from substance to substance. If more than one type of element is bonded, we call it a compound.
Chemical bonds form because
Atoms like to have full valence shells (to become stable). They achieve this by sharing or transferring their electrons.
Types of bonds
Ionis: metal, nonmetal. Covalent: two nonmetals. Metallic: two metals.
Cation
Loss of electrons (positive charge).
Anion
Gain of electrons (negative charge).
Ion
At atom or molecule with an electric charge.
Law of conservation of mass
Mass cannot be formed nor destroyed.
Physical change
Changes in the appearance of a substance that are reversible and do not produce a new substance.
Chemical change
A change of materials into another, new materials with different properties and one or more than one new substances are formed.
Examples of physical change
Melting, boiling, breaking, dissolving.
Signs of a chemical change (observations)
Bubbles, cloudiness, temperature change, colour change, change in smell, precipitate (formation of a solid)
Examples of chemical change
Burning, rusting, decomposing.
Chemical properties
Combustibility, ability to burn (flammability), reactivity, acidity, toxicity, instability.
Physical properties
Appearance, melting and boiling points, density, solubility, polarity.
Synthesis
A + B -> AB
Decomposition
AB -> A + B
Combustion
fuel + O2 -> CO2 + H2O
Single replacement
X + AB -> XB + A
Double replacement
XY + AB -> XB + AY
Neutralisation
Acid + Base -> Metal Salt + Water
Acid + Reactive metal
Acid + Reactive metal -> Metal salt + hydrogen
Acid + Metal carbonate
Acid + metal carbonate -> salt + water + carbon dioxide
Pure substance
Consists only of one element or one compound.
Mixture
Consists of two or more different substances, not chemically joined together.
Homogeneous substance
A substance that has uniform composition and properties throughout.
Heterogeneous substance
A substance in which the composition is not uniform throughout.
Solute
The substance dissolved into the solvent.
Solvent
A substance in which the solute is dissolved into.
Solution
A homogeneous mixture of one or more solutes dissolved in a solvent.
Unsaturated
Not saturated; capable of absorbing or dissolving more of something
Saturated
A solution that is unable to absorb or dissolve any more of a solute at a given temperature and pressure
Supersaturated
A solution that contains more than the maximum amount of solute that is capable of being dissolved at a given temperature
Example of a solution
Sparkling water is a solution of water and carbon dioxide. Salt water.
Concentrated solution
One that has a relatively large amount of dissolved solute.
Dilute solution
One that has a relatively small amount of dissolved solute.
Process to create solutions
In chemistry, an unsaturated solution consists of solute completely dissolved in solute. If no additional solute can dissolve in a solution, that solution is said to be saturated. Solubility depends on temperature. Raising the temperature of a solution may even turn a saturated solution into an unsaturated one.
Why is a precipitate formed
When solutions containing ionic compounds are mixed and an insoluble product is formed.
pH scale
pH is a measure of how acidic/basic a substance is. The range goes from 0 - 14, with 7 being neutral. pHs of less than 7 indicate acidity, whereas a pH of greater than 7 indicates a base.
Acid
A substance that produces hydrogen ions when dissolved in water.
eg. hydrochloric acid, sulfuric acid, citric acid
Acid properties
- Sour taste
- A pH less than 7
- Turn blue litmus paper red
- Turn universal indicator red
- Corrosive
Alkaline/base
A substance that produces hydroxide ions when dissolved in water. Eg. sodium hydroxide, ammonia
Alkaline/base properties
- Turn red litmus paper blue.
- Bitter in taste.
- Conduct electricity.
- Feel slippery or soapy.
Dilute acid
The acid is mixed with water in an amount more than the acid itself. It does not reduce the reactivity of acid or make it weaker. It reduces the amount of acid in the solution
Concentrated acid
One in which many acid molecules are dissolved in a set volume of solution
Concentrated base
An aqueous solution which has a relatively high percentage of the base
Dilute base
An aqueous solution which has a relatively low percentage of the base
Chemical test for hydrogen gas
Pop test: Hydrogen gas is highly flammable You can safely test for small quantities of hydrogen gas (eg collected in a test tube) by holding a burning splint near to the top of the test tube. The positive result is a squeaky pop sound as the hydrogen reacts with oxygen in the air in a small explosion.
Chemical test for carbon dioxide gas
Limewater test: Carbon dioxide reacts with calcium hydroxide solution to produce a white precipitate of calcium carbonate. Limewater is a solution of calcium hydroxide. If carbon dioxide is bubbled through limewater, the limewater turns milky or cloudy white.
Chemical reactions in relation with stuff
Chemical reactions, including combustion and the reactions of acids, are important in both nonliving and living systems and involve energy transfer.
Chemical reactions in living systems
Are needed to digest food, for plants to grow (photosynthesis).
