Science Sem 2 Year 10

Law of Conservation of Mass

The law of conservation of mass states that in a chemical reaction, mass is neither created nor destroyed. This is why chemical equations must be balanced.

Endothermic and Exothermic reactions

Endothermic reactions absorb energy, while exothermic reactions release energy.

Activation energy

The minimum energy required for a reaction to begin is called activation energy. Once the activation energy has been reached, the reactants have enough energy to collide with each other and form products.

Complete combustion

Complete combustion occurs when fuels react with an excess supply of oxygen and produce water vapor and carbon dioxide.

Rates of Chemical Reactions

The rate of reaction is described as the speed at which a chemical reaction takes place. It can be found by measuring the amount of reactant used up or the amount of product formed in a given time.

Collision theory

For a chemical reaction to occur, the reactant particles must collide. Successful reactions occur when the particles have enough energy and the rate of reaction depends on the rate of successful collisions between reactant particles.

Factors that affect rate of reaction

Factors such as temperature, concentration of reactants, surface area of reactants, and agitation can affect the rate of reaction.

Current

Current is a continuous loop of electrons flowing through a circuit, which requires a power source, conducting material, and a load.

Electromagnetism

Electromagnetism is the interaction between electric currents and magnetic fields. It involves the production of magnetic fields by electric currents and the production of electric currents by changing magnetic fields.

Ohm's Law

Ohm's Law states that the current flowing through a conductor is directly proportional to the voltage across the conductor and inversely proportional to the resistance of the conductor.

Variation within species

Members of the same species show variation in their traits or characteristics, which can be caused by a combination of inherited and environmental factors.

Asexual reproduction

Asexual reproduction does not involve the union of gametes and offspring come from one parent organism only. Offspring are mostly genetically identical to parents.

Sexual reproduction

Sexual reproduction involves the union of gametes to combine genetic information from two parents. Offspring show a great deal of genetic diversity because of the combination of genes from parents.

Mitosis

Mitosis is a simple cell division in body cells, where the DNA is replicated and split between two cells. Daughter cells are identical to parent cells in number of chromosomes and genetic information.

Meiosis

Meiosis is cell division in sex cells, where the DNA is replicated and split between two cells, each of which splits again. Daughter cells are non-identical to parent cells in number of chromosomes and genetic information.

Gene

A gene is a specific sequence of nucleotides found on a chromosome that codes for a specific trait or characteristic in a living thing.

Allele

Alleles are the different versions of a gene.

Dominant

Dominant alleles will be expressed if present in an individual.

Recessive

Recessive alleles will be covered up by dominant alleles if both are present and will only be expressed if both alleles are recessive.

Gregor Mendel

Gregor Mendel was an Austrian monk who conducted extensive experiments on pea plants and discovered patterns of inheritance. He is known as the father of modern genetics.

Mendel's breakthrough

Recognized pattern in inheritance of characteristics and proposed model of inheritance.

Genotype

Combination of two alleles an individual has for a specific trait.

Homozygous

Both alleles of the genotype are the same.

Heterozygous

The alleles of the genotype are different.

Phenotype

Observable characteristic expressed in an individual, controlled by genotype.

Variation

Differences between individuals within a species.

Evolution

Process by which different kinds of living organisms develop from earlier forms.

Natural Selection

Organisms with favorable characteristics survive longer and pass down these traits to offspring.

Species

Group of organisms that can interbreed and produce fertile offspring.

Divergent evolution

Differences in closely related species, indicating recent divergence from a common ancestor.

Convergent evolution

Similarities in distantly related species, indicating adaptation to similar environments.

Extinction

Occurs when no remaining individuals of a species are alive.

Speciation

Formation of a new species through isolation and evolution under different selection pressures.

Biosphere

Life-support system of the planet, including the atmosphere, lithosphere, hydrosphere, and biota.

Atmosphere

Divided into the troposphere and stratosphere, with the ozone layer.

Human activity and the atmosphere

Release of chlorofluorocarbons leading to ozone depletion and increased UV radiation.

Human activity and the hydrosphere

Toxic or industrial wastes and untreated sewage impacting water systems and organisms.

Lithosphere

Earth's soil, rocky crust, and upper mantle, where rocks are formed, broken down, and changed.

Human activity and the lithosphere

Overstocking, soil erosion, deforestation, and chemical emissions impacting habitats and resources.

Carbon Cycle

Importance of carbon in living cells, fuel, and common reactions like respiration, photosynthesis, and combustion.

Nitrogen Cycle

Importance of nitrogen in building proteins, its abundance in the atmosphere, and its cycling through organisms and soil.