Chemistry Notes – Grade 10
National Curriculum Pakistan - NCP
Chapter 1: History of Chemistry
Aligned with National Curriculum Pakistan (Federal Board, NBF, PTB)
- What is the conservation of mass and energy and who introduced the principle of conservation of mass in chemistry?
Antoine Lavoisier in the 18th century proposed the law of conservation of mass and energy. It states that mass and energy cannot be created or destroyed in a closed system. For example, in a chemical reaction, the total mass of the reactants is always equal to the total mass of the products. If an experiment doesn't follow this rule, chemists check their procedure and calculations to find out what went wrong. - What is the difference between repeatability and reproducibility in chemistry?
Repeatability: Scientific results should be verifiable by conducting the same experiment under the same physical conditions.
Reproducibility: Similar results should be obtained under different conditions, methods, or experiments. - What is the role of observation and logical thinking in chemistry and who is Dmitri Mendeleev?
Observation and logical thinking help chemists make sense of their findings. Dmitri Mendeleev created the periodic table by observing patterns in the properties of elements. He even predicted elements that hadn't been discovered yet based on these patterns. - How do controlled experiments help in pharmaceutical chemistry?
Controlled experiments in pharmaceutical chemistry are used to test if new medicines work and are safe. This method is also used in other sciences like biology and physics to test ideas and find cause-and-effect relationships. - What is the importance of controlled experiments in chemistry?
Chemists, like other scientists, use controlled experiments to test their ideas. They change one variable at a time while keeping others constant to observe the effects. - Why is objectivity important in chemistry?
Objectivity ensures that results are based on precise measurements and standard methods, reducing bias and increasing reliability. - Why are scientists naturally skeptical?
Scientists are naturally skeptical and always double-check new discoveries to ensure that only trustworthy information becomes part of science. They repeat experiments and conduct tests to verify results, ensuring reliability. - What is a scientific paradigm?
A scientific paradigm is a set of ideas, methods, and rules that guide scientists in their research. It helps them understand the natural world and explain their discoveries. - What is phlogiston theory?
In the 1700s, scientists believed in the phlogiston theory to explain burning (combustion) and rusting. According to this theory, materials that could burn contained a substance called "phlogiston," which was released during burning. For example, when metals rusted, it was believed they absorbed "dephlogisticated air." - Who disproved the Phlogiston Theory?
Antoine Lavoisier disproved the phlogiston theory. He proved that combustion occurs because of oxygen combining with substances, not due to phlogiston. His work introduced modern concepts of oxidation and reduction. - Give a short view of the historical models of the atom.
Plum Pudding Model (1904): J.J. Thomson suggested that atoms are like a pudding with negatively charged electrons ("plums") scattered in a positively charged "soup."
Rutherford’s Model (1911): Ernest Rutherford’s gold foil experiment showed that atoms have a small, dense, positively charged nucleus with electrons orbiting around it.
Bohr’s Model and Quantum Model: Later models added the idea of energy levels (Bohr) and eventually led to quantum mechanics, which is the modern understanding of atoms. - What do confidence intervals show?
Confidence intervals show how precise a measurement is. For example, if a pharmacist measures a solution's concentration as 0.50 molar with a 95% confidence interval of 0.48–0.52 molar, it means they are 95% sure the true value lies within that range. - What do p-values help to determine?
P-values help scientists check if experimental results are meaningful. For instance, if a catalyst test gives a p-value of 0.01, it means there's only a 1% chance the result is random—indicating the result is statistically significant. - What does Bayesian probability do?
Bayesian probability updates confidence in an idea based on new evidence. For example, a chemist may believe there's a 60% chance a reaction occurs a certain way, but if new data increases confidence to 80%, they have used Bayesian probability. - What does uncertainty tell us?
Uncertainty tells us how reliable a measurement is. For instance, if a solution’s concentration is measured as 0.250 molar ± 0.005 molar, it shows the possible error range in the measurement.
Tags
Antoine Lavoisier
Bohr model
confidence intervals in chemistry
historical atomic models
J.J. Thomson
phlogiston theory
quantum model of atom
Rutherford model