Pure substances and mixtures

Imagine you have a box of plastic counters. Some of them are green, some blue, some red and some yellow. If each counter represented a different substance we would say we had a mixture. We have a mixture when there is more than one substance in our container.

Pure substances and mixtures

The colloid particles are attracted toward water. They are also called reversible sols. These are opposite in nature to hydrophilic colloids.

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The colloid particles are repelled by water. They are also called irreversible sols. In some cases, a colloid suspension can be considered a homogeneous mixture. This is because the distinction between "dissolved" and "particulate" matter can be sometimes a matter of approach, which affects whether or not it is homogeneous or heterogeneous.

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Interaction between particles The following forces play an important role in the interaction of colloid particles: This refers to the impossibility of any overlap between hard particles. Colloidal particles often carry an electrical charge and therefore attract or repel each other. The charge of both the continuous and the dispersed phase, as well as the mobility of the phases are factors affecting this interaction.

This is due to interaction between two dipoles that are either permanent or induced. Even if the particles do not have a permanent dipole, fluctuations of the electron density gives rise to a temporary dipole in a particle.

This temporary dipole induces a dipole in particles nearby. The temporary dipole and the induced dipoles are then attracted to each other. This is known as van der Waals force, and is always present unless the refractive indexes of the dispersed and continuous phases are matchedis short-range, and is attractive.

According to the second law of thermodynamics, a system progresses to a state in which entropy is maximized. This can result in effective forces even between hard spheres[ how? Steric forces between polymer-covered surfaces or in solutions containing non-adsorbing polymer can modulate interparticle forces, producing an additional steric repulsive force which is predominantly entropic in origin or an attractive depletion force between them.

Such an effect is specifically searched for with tailor-made superplasticizers developed to increase the workability of concrete and to reduce its water content.

Preparation There are two principal ways of preparation of colloids: Condensation of small dissolved molecules into larger colloidal particles by precipitation, condensation, or redox reactions.

Pure substances and mixtures

Such processes are used in the preparation of colloidal silica or gold. Stabilization peptization The stability of a colloidal system is defined by particles remaining suspended in solution at equilibrium.

Stability is hindered by aggregation and sedimentation phenomena, which are driven by the colloid's tendency to reduce surface energy. Reducing the interfacial tension will stabilize the colloidal system by reducing this driving force.Melting Point and Freezing Point. Pure, crystalline solids have a characteristic melting point, the temperature at which the solid melts to become a plombier-nemours.com transition between the solid and the liquid is so sharp for small samples of a pure substance that melting points can be measured to o C.

The melting point of solid oxygen, for example, is o C. Water is a pure substance, if you put sand into a glass of water, it would turn into a mixture.

More facts and examples of pure substances and mixtures. Water is a pure substance, if you put sand into a glass of water, it would turn into a mixture. More facts and examples of pure substances and mixtures.

An important property of mixtures is that they can (usually) be separated into their individual components without requiring any chemical reactions. For example, we can evaporate our sugar-water solution to obtain pure water or pure sugar.

Likewise, we could put our chocolate chip cookie into water to dissolve away the dough and collect pure chocolate chips. Aug 30,  · Pure substances cannot be separated into any other kinds of matter, while a mixture is a combination of two or more pure substances.

2. A pure substance has constant physical and chemical properties, while mixtures have varying physical and chemical properties (i.e., boiling point and melting point). Matter is composed of tiny particles called atoms and there are about naturally occurring types of atoms called elements.

Elements are shown in the periodic table and are either metals or non-metals.

Pure Substances and Mixtures - Chemistry for Kids | Mocomi