The scientific method and the properties of gases

Scientific method The scientific method is a step by step procedure used by scientists to solve problems. It includes observation, statement of the problem, hypothesis, experimentation and drawing conclusions such theories and laws.

Over the past four centuries, scientists have performed many experiments to understand the common behaviors of gases. They have observed that a gas's physical condition—its state—depends on four variables: pressure (P), volume (V), temperature (T), and amount of gas.

Is not the learning of facts, but the training of the mind to think! Observation: facts Education Is not the learning of facts, but the training of the mind to think! Albert Einstein Properties of gases They adopt the shape of the container. They occupy all the available volume. They exert pressure

Observation: facts In a gas the magnitudes of Pressure (Pascal or atmospheres) Volume (m3 or l) Temperature (Kelvin) are connected and if we change one of the others will change.

The mass and temperature of the gas don’t change Experiment Materials and Procedure Variable This is the magnitude .... Independent (manipulated) pressure I will change during the experiment. It is the only one that I should change. Dependent (responding) volume It could change as a consequence. I will measure during the experiment. control Mass temperature These never change (in this experiment) manometer Graduated container Drag this Variables are anything that might change or be changed in an experiment. The mass and temperature of the gas don’t change

Data and graphs

Simulation of the experiment Below is a Boyle's Law applet like the syringe we played with in class that allows you to explore the relationship between pressure and volume along with a graph of the data. click image to launch apple

When the pressure increases the volume decreases Drawing conclusions When the pressure increases the volume decreases P.V seems to be constant

Many scientific laws can be expressed as a mathematical equation Formulation of laws The Boyle-Mariotte law states that …… Many scientific laws can be expressed as a mathematical equation For the same mass of gas at a constante temperature, when the pressure increases, the volume of the gas decreases, and vice versa

Statement of hypothesis In general, a scientific law is the description of an observed phenomenon. It doesn't explain WHY the phenomenon exists or what causes it. A hypothesis is a supposition which attempts to explain an observed phenomenon.

Theories The explanation of a phenomenon is called a scientific theory. In science, a theory is an explanation that generally is accepted to be true but theories can change over time when new data are found.

The kinetic Theory of matter- Gases The kinetic theory explains the Boyle’s Law

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When the gas is heated its particles move faster and the energy and number of the collisions with the container wall increase.

Science is a collective enterprise

The Kinetic Theory of matter Explain the properties of the different states of aggregation and the change of state.

The Kinetic Theory of matter