Learn: Chemistry Reactions and Alkanes: Formulas, Combustion, and Precipitates

Atom

A tiny particle that makes up matter.

Element

A substance containing only one type of atom.

Compound

Two or more different elements chemically joined.

Chemical reaction

A process where atoms rearrange to form new substances.

Hydrocarbon

A compound containing only carbon and hydrogen.

Alkane

A hydrocarbon with only single bonds between carbon atoms.

Alkane general formula

CnH2n+2

Methane

CH4

Ethane

C2H6

Propane

C3H8

Butane

C4H10

Pentane

C5H12

Hexane

C6H14

Heptane

C7H16

Octane

C8H18

Structural formula

Shows how atoms are connected by bonds.

Covalent bond

A bond where atoms share electrons.

How many bonds does carbon form?

4 bonds.

How many bonds does hydrogen form?

1 bond.

How many bonds does oxygen normally form?

2 bonds.

Alcohol

An organic compound containing an -OH group.

Hydroxyl group

The -OH group found in alcohols.

Methanol

CH3OH

Ethanol

C2H5OH

Combustion

A reaction where fuel reacts with oxygen and releases energy.

Complete combustion

Burning with plenty of oxygen.

Products of complete combustion

Carbon dioxide and water.

Incomplete combustion

Burning with limited oxygen.

Products of incomplete combustion

Carbon monoxide and/or carbon (soot), plus water.

Complete combustion flame

Usually blue and clean.

Incomplete combustion flame

Often yellow or orange and smoky.

Why is incomplete combustion dangerous?

It can produce poisonous carbon monoxide.

How do you test for carbon dioxide?

Limewater turns milky or cloudy.

How do you test for water?

Blue cobalt chloride paper turns pink.

How do you balance combustion equations?

Balance carbon, then hydrogen, then oxygen.

Greenhouse effect

Greenhouse gases absorb and re-emit infrared radiation, warming Earth.

What increases the greenhouse effect?

Extra carbon dioxide from burning fossil fuels.

Combination reaction

Two or more reactants join to make one product.

Combination reaction pattern

A + B → AB

Magnesium + oxygen

Produces magnesium oxide.

Magnesium oxide colour

White.

Copper + oxygen

Produces copper oxide.

Copper oxide colour

Black.

Displacement reaction

A more reactive metal replaces a less reactive metal in a compound.

Displacement reaction pattern

A + BC → AC + B

What determines if displacement occurs?

The reactivity of the metals.

What happens when magnesium reacts with copper sulfate?

Magnesium replaces copper.

What happens when copper reacts with silver nitrate?

Copper replaces silver.

Precipitate

An insoluble solid formed when solutions react.

Precipitation reaction

Two solutions react to form an insoluble solid.

What does (aq) mean?

Dissolved in water.

What does (s) mean?

Solid.

What is solubility?

How well a substance dissolves in water.

What do nitrates usually do?

Dissolve in water.

What do most carbonates do?

Do not dissolve in water.

What do most hydroxides do?

Do not dissolve in water.

What colour is a copper(II) precipitate?

Blue.

What colour is an iron(II) precipitate?

Green.

What colour is an iron(III) precipitate?

Orange-brown.

What can a white precipitate that dissolves in excess sodium hydroxide indicate?

Aluminium ions.

What does sodium hydroxide provide?

Hydroxide ions (OH-).What does DNA stand for? Deoxyribonucleic acid.

What is DNA?

The molecule that stores genetic instructions.

Where is most DNA found?

In the nucleus.

What shape is DNA?

A double helix.

What are the four DNA bases?

Adenine, thymine, cytosine and guanine.

What does A pair with?

T.

What does C pair with?

G.

What is a nucleotide?

A unit that makes up DNA.

What does DNA's base sequence do?

Stores genetic information.

What is a chromosome?

A long DNA molecule packaged with proteins.

What is a gene?

A section of DNA that contributes to a functional product or characteristic.

What is an allele?

A version of a gene.

What is a genome?

An organism's complete genetic material.

What is genotype?

The alleles an organism has.

What is phenotype?

An observable characteristic.

What is a dominant allele?

An allele that can affect the phenotype with one copy.

What is a recessive allele?

An allele that usually affects the phenotype when two copies are present.

What is homozygous?

Having two identical alleles.

What is heterozygous?

Having two different alleles.

What is a mutation?

A change in the DNA sequence.

How can mutations create variation?

They can create new alleles.

Which mutations can be inherited?

Mutations in cells that contribute to sperm or eggs.

What is genetic variation?

Differences in alleles between individuals in a population.

What is meiosis?

Cell division that produces gametes.

How many chromosomes are in human body cells?

46.

How many chromosomes are in human gametes?

23.

What is independent assortment?

Chromosome pairs separate into different combinations.

What is crossing over?

Matching chromosomes exchange sections of DNA.

What is fertilisation?

A sperm and egg join together.

How does sexual reproduction create variation?

Offspring receive different combinations of alleles from two parents.

What is a Punnett square?

A grid used to predict possible offspring genotypes.

What is the genotype ratio of Bb x Bb?

1 BB : 2 Bb : 1 bb.

What is the phenotype ratio of Bb x Bb?

3 dominant : 1 recessive.

What is natural selection?

Individuals with helpful inherited traits tend to survive and reproduce more.

What happens to helpful alleles over generations?

They may become more common.

What is a selection pressure?

An environmental factor affecting survival or reproduction.

What is the bottleneck effect?

A population becomes smaller and loses genetic variation.

What can cause a bottleneck effect?

Disease, natural disasters or habitat destruction.

Why is genetic variation important?

It helps populations respond to environmental changes.

What is DNA sequencing?

Finding the order of DNA bases.